| Message ID | 1413399924-599-1-git-send-email-prarit@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
Hi Prarit, On Wed, Oct 15, 2014 at 1:05 PM, Prarit Bhargava <prarit@redhat.com> wrote: > Consider a multi-node, multiple pci root bridge system which can be > configured into one large node or one node/socket. When configuring the > system the numa_node value for each PCI root bridge is always set > incorrectly to -1, or NUMA_NO_NODE, rather than to the node value of each > socket. Each PCI device inherits the numa value directly from it's parent > device, so that the NUMA_NO_NODE value is passed through the entire PCI > tree. > > Some new drivers, such as the Intel QAT driver, drivers/crypto/qat, > require that a specific node be assigned to the device in order to > achieve maximum performance for the device, and will fail to load if the > device has NUMA_NO_NODE. It seems ... unfriendly for a driver to fail to load just because it can't guarantee maximum performance. Out of curiosity, where does this actually happen? I had a quick look for NUMA_NO_NODE and module_init() functions in drivers/crypto/qat, and I didn't see the spot. > The driver would load if the numa_node value > was equal to or greater than -1 and quickly hacking the driver results in > a functional QAT driver. > > Using lspci and numactl it is easy to determine what the numa value should > be. The problem is that there is no way to set it. This patch adds a > store function for the PCI device's numa_node value. I'm not familiar with numactl. It sounds like it can show you the NUMA topology? Where does that information come from? > To use this, one can do > > echo 3 > /sys/devices/pci0000:ff/0000:ff:1f.3/numa_node > > to set the numa node for PCI device 0000:ff:1f.3. It definitely seems wrong that we don't set the node number correctly. pci_acpi_scan_root() sets the node number by looking for a _PXM method that applies to the host bridge. Why does that not work in this case? Does the BIOS not supply _PXM? If there's information that numactl uses, maybe the kernel should use that, too? A sysfs interface might be a useful workaround, but obviously it would be far better if we could fix the BIOS and/or kernel so the workaround isn't necessary in the first place. Bjorn > Cc: Myron Stowe <mstowe@redhat.com> > Cc: Bjorn Helgaas <bhelgaas@google.com> > Cc: linux-pci@vger.kernel.org > Signed-off-by: Prarit Bhargava <prarit@redhat.com> > --- > drivers/pci/pci-sysfs.c | 23 ++++++++++++++++++++++- > 1 file changed, 22 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c > index 92b6d9a..c05ed30 100644 > --- a/drivers/pci/pci-sysfs.c > +++ b/drivers/pci/pci-sysfs.c > @@ -221,12 +221,33 @@ static ssize_t enabled_show(struct device *dev, struct device_attribute *attr, > static DEVICE_ATTR_RW(enabled); > > #ifdef CONFIG_NUMA > +static ssize_t numa_node_store(struct device *dev, > + struct device_attribute *attr, > + const char *buf, size_t count) > +{ > + int node, ret; > + > + if (!capable(CAP_SYS_ADMIN)) > + return -EPERM; > + > + ret = kstrtoint(buf, 0, &node); > + if (ret) > + return ret; > + > + if (!node_online(node)) > + return -EINVAL; > + > + dev->numa_node = node; > + > + return count; > +} > + > static ssize_t numa_node_show(struct device *dev, struct device_attribute *attr, > char *buf) > { > return sprintf(buf, "%d\n", dev->numa_node); > } > -static DEVICE_ATTR_RO(numa_node); > +static DEVICE_ATTR_RW(numa_node); > #endif > > static ssize_t dma_mask_bits_show(struct device *dev, > -- > 1.7.9.3 > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 10/15/2014 03:23 PM, Bjorn Helgaas wrote: > Hi Prarit, > > On Wed, Oct 15, 2014 at 1:05 PM, Prarit Bhargava <prarit@redhat.com> wrote: >> Consider a multi-node, multiple pci root bridge system which can be >> configured into one large node or one node/socket. When configuring the >> system the numa_node value for each PCI root bridge is always set >> incorrectly to -1, or NUMA_NO_NODE, rather than to the node value of each >> socket. Each PCI device inherits the numa value directly from it's parent >> device, so that the NUMA_NO_NODE value is passed through the entire PCI >> tree. >> >> Some new drivers, such as the Intel QAT driver, drivers/crypto/qat, >> require that a specific node be assigned to the device in order to >> achieve maximum performance for the device, and will fail to load if the >> device has NUMA_NO_NODE. > > It seems ... unfriendly for a driver to fail to load just because it > can't guarantee maximum performance. Out of curiosity, where does > this actually happen? I had a quick look for NUMA_NO_NODE and > module_init() functions in drivers/crypto/qat, and I didn't see the > spot. The whole point of the Intel QAT driver is to guarantee max performance. If that is not possible the driver should not load (according to the thread mentioned below) > >> The driver would load if the numa_node value >> was equal to or greater than -1 and quickly hacking the driver results in >> a functional QAT driver. >> >> Using lspci and numactl it is easy to determine what the numa value should >> be. The problem is that there is no way to set it. This patch adds a >> store function for the PCI device's numa_node value. > > I'm not familiar with numactl. It sounds like it can show you the > NUMA topology? Where does that information come from? You can map at least what nodes are available (although I suppose you can get the same information from dmesg). You have to do a bit of hunting through the PCI tree to determine the root PCI devices, but you can determine which root device is connected to which node. > >> To use this, one can do >> >> echo 3 > /sys/devices/pci0000:ff/0000:ff:1f.3/numa_node >> >> to set the numa node for PCI device 0000:ff:1f.3. > > It definitely seems wrong that we don't set the node number correctly. > pci_acpi_scan_root() sets the node number by looking for a _PXM method > that applies to the host bridge. Why does that not work in this case? > Does the BIOS not supply _PXM? Yeah ... unfortunately the BIOS is broken in this case. And I know what you're thinking ;) -- why not get the BIOS fixed? I'm through relying on BIOS fixes which can take six months to a year to appear in a production version... I've been bitten too many times by promises of BIOS fixes that never materialize. We have systems that only have a support cycle of 3 years, and things like ACPI _PXM updates are at the bottom of the list :/. FWIW, on this particular system I have a filed a bug with the vendor. > > If there's information that numactl uses, maybe the kernel should use that, too? > > A sysfs interface might be a useful workaround, but obviously it would > be far better if we could fix the BIOS and/or kernel so the workaround > isn't necessary in the first place. Yep ... but like I said, I don't think anyone wants to wait a year. What if we never see a fix? Side issue: While investigating this I noticed that plain kmalloc() is used in the setup code. Is there a reason we don't use kmalloc_node() in pci_alloc_dev(), and other allocation functions? It seems like we should be to optimize system performance. OTOH ... I haven't done any measurements to see if it actually makes a difference :) P. > > Bjorn > >> Cc: Myron Stowe <mstowe@redhat.com> >> Cc: Bjorn Helgaas <bhelgaas@google.com> >> Cc: linux-pci@vger.kernel.org >> Signed-off-by: Prarit Bhargava <prarit@redhat.com> >> --- >> drivers/pci/pci-sysfs.c | 23 ++++++++++++++++++++++- >> 1 file changed, 22 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c >> index 92b6d9a..c05ed30 100644 >> --- a/drivers/pci/pci-sysfs.c >> +++ b/drivers/pci/pci-sysfs.c >> @@ -221,12 +221,33 @@ static ssize_t enabled_show(struct device *dev, struct device_attribute *attr, >> static DEVICE_ATTR_RW(enabled); >> >> #ifdef CONFIG_NUMA >> +static ssize_t numa_node_store(struct device *dev, >> + struct device_attribute *attr, >> + const char *buf, size_t count) >> +{ >> + int node, ret; >> + >> + if (!capable(CAP_SYS_ADMIN)) >> + return -EPERM; >> + >> + ret = kstrtoint(buf, 0, &node); >> + if (ret) >> + return ret; >> + >> + if (!node_online(node)) >> + return -EINVAL; >> + >> + dev->numa_node = node; >> + >> + return count; >> +} >> + >> static ssize_t numa_node_show(struct device *dev, struct device_attribute *attr, >> char *buf) >> { >> return sprintf(buf, "%d\n", dev->numa_node); >> } >> -static DEVICE_ATTR_RO(numa_node); >> +static DEVICE_ATTR_RW(numa_node); >> #endif >> >> static ssize_t dma_mask_bits_show(struct device *dev, >> -- >> 1.7.9.3 >> > > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 10/15/2014 03:47 PM, Prarit Bhargava wrote: > On 10/15/2014 03:23 PM, Bjorn Helgaas wrote: >> Hi Prarit, >> >> On Wed, Oct 15, 2014 at 1:05 PM, Prarit Bhargava <prarit@redhat.com> wrote: >>> Consider a multi-node, multiple pci root bridge system which can be >>> configured into one large node or one node/socket. When configuring the >>> system the numa_node value for each PCI root bridge is always set >>> incorrectly to -1, or NUMA_NO_NODE, rather than to the node value of each >>> socket. Each PCI device inherits the numa value directly from it's parent >>> device, so that the NUMA_NO_NODE value is passed through the entire PCI >>> tree. >>> >>> Some new drivers, such as the Intel QAT driver, drivers/crypto/qat, >>> require that a specific node be assigned to the device in order to >>> achieve maximum performance for the device, and will fail to load if the >>> device has NUMA_NO_NODE. >> >> It seems ... unfriendly for a driver to fail to load just because it >> can't guarantee maximum performance. Out of curiosity, where does >> this actually happen? I had a quick look for NUMA_NO_NODE and >> module_init() functions in drivers/crypto/qat, and I didn't see the >> spot. > > The whole point of the Intel QAT driver is to guarantee max performance. If > that is not possible the driver should not load (according to the thread > mentioned below) > Whups. This thread: http://marc.info/?l=linux-crypto-vger&m=141279031626999&w=2 >> >>> The driver would load if the numa_node value >>> was equal to or greater than -1 and quickly hacking the driver results in >>> a functional QAT driver. >>> >>> Using lspci and numactl it is easy to determine what the numa value should >>> be. The problem is that there is no way to set it. This patch adds a >>> store function for the PCI device's numa_node value. >> >> I'm not familiar with numactl. It sounds like it can show you the >> NUMA topology? Where does that information come from? > > You can map at least what nodes are available (although I suppose you can get > the same information from dmesg). You have to do a bit of hunting through the > PCI tree to determine the root PCI devices, but you can determine which root > device is connected to which node. > >> >>> To use this, one can do >>> >>> echo 3 > /sys/devices/pci0000:ff/0000:ff:1f.3/numa_node >>> >>> to set the numa node for PCI device 0000:ff:1f.3. >> >> It definitely seems wrong that we don't set the node number correctly. >> pci_acpi_scan_root() sets the node number by looking for a _PXM method >> that applies to the host bridge. Why does that not work in this case? >> Does the BIOS not supply _PXM? > > Yeah ... unfortunately the BIOS is broken in this case. And I know what you're > thinking ;) -- why not get the BIOS fixed? I'm through relying on BIOS fixes > which can take six months to a year to appear in a production version... I've > been bitten too many times by promises of BIOS fixes that never materialize. > > We have systems that only have a support cycle of 3 years, and things like ACPI > _PXM updates are at the bottom of the list :/. > > FWIW, on this particular system I have a filed a bug with the vendor. > >> >> If there's information that numactl uses, maybe the kernel should use that, too? >> >> A sysfs interface might be a useful workaround, but obviously it would >> be far better if we could fix the BIOS and/or kernel so the workaround >> isn't necessary in the first place. > > Yep ... but like I said, I don't think anyone wants to wait a year. What if we > never see a fix? > > Side issue: While investigating this I noticed that plain kmalloc() is used in > the setup code. Is there a reason we don't use kmalloc_node() in > pci_alloc_dev(), and other allocation functions? It seems like we should be to > optimize system performance. OTOH ... I haven't done any measurements to see if > it actually makes a difference :) > > P. > >> >> Bjorn >> >>> Cc: Myron Stowe <mstowe@redhat.com> >>> Cc: Bjorn Helgaas <bhelgaas@google.com> >>> Cc: linux-pci@vger.kernel.org >>> Signed-off-by: Prarit Bhargava <prarit@redhat.com> >>> --- >>> drivers/pci/pci-sysfs.c | 23 ++++++++++++++++++++++- >>> 1 file changed, 22 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c >>> index 92b6d9a..c05ed30 100644 >>> --- a/drivers/pci/pci-sysfs.c >>> +++ b/drivers/pci/pci-sysfs.c >>> @@ -221,12 +221,33 @@ static ssize_t enabled_show(struct device *dev, struct device_attribute *attr, >>> static DEVICE_ATTR_RW(enabled); >>> >>> #ifdef CONFIG_NUMA >>> +static ssize_t numa_node_store(struct device *dev, >>> + struct device_attribute *attr, >>> + const char *buf, size_t count) >>> +{ >>> + int node, ret; >>> + >>> + if (!capable(CAP_SYS_ADMIN)) >>> + return -EPERM; >>> + >>> + ret = kstrtoint(buf, 0, &node); >>> + if (ret) >>> + return ret; >>> + >>> + if (!node_online(node)) >>> + return -EINVAL; >>> + >>> + dev->numa_node = node; >>> + >>> + return count; >>> +} >>> + >>> static ssize_t numa_node_show(struct device *dev, struct device_attribute *attr, >>> char *buf) >>> { >>> return sprintf(buf, "%d\n", dev->numa_node); >>> } >>> -static DEVICE_ATTR_RO(numa_node); >>> +static DEVICE_ATTR_RW(numa_node); >>> #endif >>> >>> static ssize_t dma_mask_bits_show(struct device *dev, >>> -- >>> 1.7.9.3 >>> >> >> > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Oct 15, 2014 at 1:47 PM, Prarit Bhargava <prarit@redhat.com> wrote: > On 10/15/2014 03:23 PM, Bjorn Helgaas wrote: >> Hi Prarit, >> >> On Wed, Oct 15, 2014 at 1:05 PM, Prarit Bhargava <prarit@redhat.com> wrote: >>> Consider a multi-node, multiple pci root bridge system which can be >>> configured into one large node or one node/socket. When configuring the >>> system the numa_node value for each PCI root bridge is always set >>> incorrectly to -1, or NUMA_NO_NODE, rather than to the node value of each >>> socket. Each PCI device inherits the numa value directly from it's parent >>> device, so that the NUMA_NO_NODE value is passed through the entire PCI >>> tree. >>> >>> Some new drivers, such as the Intel QAT driver, drivers/crypto/qat, >>> require that a specific node be assigned to the device in order to >>> achieve maximum performance for the device, and will fail to load if the >>> device has NUMA_NO_NODE. >> >> It seems ... unfriendly for a driver to fail to load just because it >> can't guarantee maximum performance. Out of curiosity, where does >> this actually happen? I had a quick look for NUMA_NO_NODE and >> module_init() functions in drivers/crypto/qat, and I didn't see the >> spot. > > The whole point of the Intel QAT driver is to guarantee max performance. If > that is not possible the driver should not load (according to the thread > mentioned below) > >> >>> The driver would load if the numa_node value >>> was equal to or greater than -1 and quickly hacking the driver results in >>> a functional QAT driver. >>> >>> Using lspci and numactl it is easy to determine what the numa value should >>> be. The problem is that there is no way to set it. This patch adds a >>> store function for the PCI device's numa_node value. >> >> I'm not familiar with numactl. It sounds like it can show you the >> NUMA topology? Where does that information come from? > > You can map at least what nodes are available (although I suppose you can get > the same information from dmesg). You have to do a bit of hunting through the > PCI tree to determine the root PCI devices, but you can determine which root > device is connected to which node. Is numactl reading SRAT? SLIT? SMBIOS tables? Presumably the kernel has access to whatever information you're getting from numactl and lspci, and if so, maybe we can do the workaround automatically in the kernel. >>> To use this, one can do >>> >>> echo 3 > /sys/devices/pci0000:ff/0000:ff:1f.3/numa_node >>> >>> to set the numa node for PCI device 0000:ff:1f.3. >> >> It definitely seems wrong that we don't set the node number correctly. >> pci_acpi_scan_root() sets the node number by looking for a _PXM method >> that applies to the host bridge. Why does that not work in this case? >> Does the BIOS not supply _PXM? > > Yeah ... unfortunately the BIOS is broken in this case. And I know what you're > thinking ;) -- why not get the BIOS fixed? I'm through relying on BIOS fixes > which can take six months to a year to appear in a production version... I've > been bitten too many times by promises of BIOS fixes that never materialize. Yep, I understand. The question is how we implement a workaround so it doesn't become the accepted way to do things. Obviously we don't want people manually grubbing through numactl/lspci output or writing shell scripts to do things that *should* happen automatically. > We have systems that only have a support cycle of 3 years, and things like ACPI > _PXM updates are at the bottom of the list :/. Something's wrong with this picture. If vendors are building systems where node information is important, and the platform doesn't tell the OS what the node numbers ARE, then in my opinion, the vendor is essentially asking for low performance and is getting what he asked for, and his customers should learn that the answer is to shop elsewhere. Somewhere in the picture there needs to be a feedback loop that encourages the vendor to fix the problem. I don't see that happening yet. Having QAT fail because the platform didn't supply the information required to make it work would be a nice loop. I don't want to completely paper over the problem without providing some other kind of feedback at the same time. You're probably aware of [1], which was the same problem. Apparently it was originally reported to RedHat as [2] (which is private, so I can't read it). That led to a workaround hack for some AMD systems [3, 4]. [1] https://bugzilla.kernel.org/show_bug.cgi?id=72051 [2] https://bugzilla.redhat.com/show_bug.cgi?id=1040440 [3] http://lkml.kernel.org/r/1394053603-3724-1-git-send-email-suravee.suthikulpanit@amd.com [4] http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=94d4bb5b1397 > FWIW, on this particular system I have a filed a bug with the vendor. > >> >> If there's information that numactl uses, maybe the kernel should use that, too? >> >> A sysfs interface might be a useful workaround, but obviously it would >> be far better if we could fix the BIOS and/or kernel so the workaround >> isn't necessary in the first place. > > Yep ... but like I said, I don't think anyone wants to wait a year. What if we > never see a fix? > > Side issue: While investigating this I noticed that plain kmalloc() is used in > the setup code. Is there a reason we don't use kmalloc_node() in > pci_alloc_dev(), and other allocation functions? It seems like we should be to > optimize system performance. OTOH ... I haven't done any measurements to see if > it actually makes a difference :) Yeah, that probably would make sense. We do use kmalloc_node() for some of the host bridge stuff, thanks to 965cd0e4a5e5 ("x86, PCI, ACPI: Use kmalloc_node() to optimize for performance"). But it probably would make sense to extend that farther down, too. >>> Cc: Myron Stowe <mstowe@redhat.com> >>> Cc: Bjorn Helgaas <bhelgaas@google.com> >>> Cc: linux-pci@vger.kernel.org >>> Signed-off-by: Prarit Bhargava <prarit@redhat.com> >>> --- >>> drivers/pci/pci-sysfs.c | 23 ++++++++++++++++++++++- >>> 1 file changed, 22 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c >>> index 92b6d9a..c05ed30 100644 >>> --- a/drivers/pci/pci-sysfs.c >>> +++ b/drivers/pci/pci-sysfs.c >>> @@ -221,12 +221,33 @@ static ssize_t enabled_show(struct device *dev, struct device_attribute *attr, >>> static DEVICE_ATTR_RW(enabled); >>> >>> #ifdef CONFIG_NUMA >>> +static ssize_t numa_node_store(struct device *dev, >>> + struct device_attribute *attr, >>> + const char *buf, size_t count) >>> +{ >>> + int node, ret; >>> + >>> + if (!capable(CAP_SYS_ADMIN)) >>> + return -EPERM; >>> + >>> + ret = kstrtoint(buf, 0, &node); >>> + if (ret) >>> + return ret; >>> + >>> + if (!node_online(node)) >>> + return -EINVAL; >>> + >>> + dev->numa_node = node; >>> + >>> + return count; >>> +} >>> + >>> static ssize_t numa_node_show(struct device *dev, struct device_attribute *attr, >>> char *buf) >>> { >>> return sprintf(buf, "%d\n", dev->numa_node); >>> } >>> -static DEVICE_ATTR_RO(numa_node); >>> +static DEVICE_ATTR_RW(numa_node); >>> #endif >>> >>> static ssize_t dma_mask_bits_show(struct device *dev, >>> -- >>> 1.7.9.3 >>> >> >> > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 10/15/2014 05:20 PM, Bjorn Helgaas wrote: > On Wed, Oct 15, 2014 at 1:47 PM, Prarit Bhargava <prarit@redhat.com> wrote: >> On 10/15/2014 03:23 PM, Bjorn Helgaas wrote: >>> Hi Prarit, >>> >>> On Wed, Oct 15, 2014 at 1:05 PM, Prarit Bhargava <prarit@redhat.com> wrote: >>>> Consider a multi-node, multiple pci root bridge system which can be >>>> configured into one large node or one node/socket. When configuring the >>>> system the numa_node value for each PCI root bridge is always set >>>> incorrectly to -1, or NUMA_NO_NODE, rather than to the node value of each >>>> socket. Each PCI device inherits the numa value directly from it's parent >>>> device, so that the NUMA_NO_NODE value is passed through the entire PCI >>>> tree. >>>> >>>> Some new drivers, such as the Intel QAT driver, drivers/crypto/qat, >>>> require that a specific node be assigned to the device in order to >>>> achieve maximum performance for the device, and will fail to load if the >>>> device has NUMA_NO_NODE. >>> >>> It seems ... unfriendly for a driver to fail to load just because it >>> can't guarantee maximum performance. Out of curiosity, where does >>> this actually happen? I had a quick look for NUMA_NO_NODE and >>> module_init() functions in drivers/crypto/qat, and I didn't see the >>> spot. >> >> The whole point of the Intel QAT driver is to guarantee max performance. If >> that is not possible the driver should not load (according to the thread >> mentioned below) >> >>> >>>> The driver would load if the numa_node value >>>> was equal to or greater than -1 and quickly hacking the driver results in >>>> a functional QAT driver. >>>> >>>> Using lspci and numactl it is easy to determine what the numa value should >>>> be. The problem is that there is no way to set it. This patch adds a >>>> store function for the PCI device's numa_node value. >>> >>> I'm not familiar with numactl. It sounds like it can show you the >>> NUMA topology? Where does that information come from? >> >> You can map at least what nodes are available (although I suppose you can get >> the same information from dmesg). You have to do a bit of hunting through the >> PCI tree to determine the root PCI devices, but you can determine which root >> device is connected to which node. > > Is numactl reading SRAT? SLIT? SMBIOS tables? Presumably the kernel > has access to whatever information you're getting from numactl and > lspci, and if so, maybe we can do the workaround automatically in the > kernel. I'll go figure that out ... > >>>> To use this, one can do >>>> >>>> echo 3 > /sys/devices/pci0000:ff/0000:ff:1f.3/numa_node >>>> >>>> to set the numa node for PCI device 0000:ff:1f.3. >>> >>> It definitely seems wrong that we don't set the node number correctly. >>> pci_acpi_scan_root() sets the node number by looking for a _PXM method >>> that applies to the host bridge. Why does that not work in this case? >>> Does the BIOS not supply _PXM? >> >> Yeah ... unfortunately the BIOS is broken in this case. And I know what you're >> thinking ;) -- why not get the BIOS fixed? I'm through relying on BIOS fixes >> which can take six months to a year to appear in a production version... I've >> been bitten too many times by promises of BIOS fixes that never materialize. > > Yep, I understand. The question is how we implement a workaround so > it doesn't become the accepted way to do things. Obviously we don't > want people manually grubbing through numactl/lspci output or writing > shell scripts to do things that *should* happen automatically. > >> We have systems that only have a support cycle of 3 years, and things like ACPI >> _PXM updates are at the bottom of the list :/. > > > Somewhere in the picture there needs to be a feedback loop that > encourages the vendor to fix the problem. I don't see that happening > yet. Having QAT fail because the platform didn't supply the > information required to make it work would be a nice loop. I don't > want to completely paper over the problem without providing some other > kind of feedback at the same time. Okay -- I see what you're after here and I completely agree with it. But sometimes I feel like I banging on a silent drum with some of these companies about this stuff :( My frustration with these companies is starting to show I guess... > > You're probably aware of [1], which was the same problem. Apparently > it was originally reported to RedHat as [2] (which is private, so I > can't read it). That led to a workaround hack for some AMD systems > [3, 4]. Yeah ... part of me was thinking that maybe I should do something like the above but I didn't know how you'd feel about expanding that hack. I'll look into it. I'd prefer it to be opt-in with a kernel parameter. P. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 10/16/2014 05:32 AM, Prarit Bhargava wrote: > On 10/15/2014 05:20 PM, Bjorn Helgaas wrote: >> On Wed, Oct 15, 2014 at 1:47 PM, Prarit Bhargava <prarit@redhat.com> wrote: >>> On 10/15/2014 03:23 PM, Bjorn Helgaas wrote: >>>> Hi Prarit, >>>> >>>> On Wed, Oct 15, 2014 at 1:05 PM, Prarit Bhargava <prarit@redhat.com> wrote: >>>>> Consider a multi-node, multiple pci root bridge system which can be >>>>> configured into one large node or one node/socket. When configuring the >>>>> system the numa_node value for each PCI root bridge is always set >>>>> incorrectly to -1, or NUMA_NO_NODE, rather than to the node value of each >>>>> socket. Each PCI device inherits the numa value directly from it's parent >>>>> device, so that the NUMA_NO_NODE value is passed through the entire PCI >>>>> tree. >>>>> >>>>> Some new drivers, such as the Intel QAT driver, drivers/crypto/qat, >>>>> require that a specific node be assigned to the device in order to >>>>> achieve maximum performance for the device, and will fail to load if the >>>>> device has NUMA_NO_NODE. >>>> It seems ... unfriendly for a driver to fail to load just because it >>>> can't guarantee maximum performance. Out of curiosity, where does >>>> this actually happen? I had a quick look for NUMA_NO_NODE and >>>> module_init() functions in drivers/crypto/qat, and I didn't see the >>>> spot. >>> The whole point of the Intel QAT driver is to guarantee max performance. If >>> that is not possible the driver should not load (according to the thread >>> mentioned below) This is just short-sighted thinking. The fact that the PCI device advertises -1 means that either the BIOS isn't configured, or the PCI slots are shared as was the case on some Nehalem systems where the IOH was shared between two sockets. I suspect that this driver doesn't even take that into account as it was likely only written for Sandy Bridge architectures. >>>>> To use this, one can do >>>>> >>>>> echo 3 > /sys/devices/pci0000:ff/0000:ff:1f.3/numa_node >>>>> >>>>> to set the numa node for PCI device 0000:ff:1f.3. >>>> It definitely seems wrong that we don't set the node number correctly. >>>> pci_acpi_scan_root() sets the node number by looking for a _PXM method >>>> that applies to the host bridge. Why does that not work in this case? >>>> Does the BIOS not supply _PXM? >>> Yeah ... unfortunately the BIOS is broken in this case. And I know what you're >>> thinking ;) -- why not get the BIOS fixed? I'm through relying on BIOS fixes >>> which can take six months to a year to appear in a production version... I've >>> been bitten too many times by promises of BIOS fixes that never materialize. >> Yep, I understand. The question is how we implement a workaround so >> it doesn't become the accepted way to do things. Obviously we don't >> want people manually grubbing through numactl/lspci output or writing >> shell scripts to do things that *should* happen automatically. I'd say if nothing else we should flag the system as tainted as soon as we start overwriting BIOS/ACPI configured values with sysfs. This is one of the reasons for the TAINT_FIRMWARE_WORKAROUND even existing. >> Somewhere in the picture there needs to be a feedback loop that >> encourages the vendor to fix the problem. I don't see that happening >> yet. Having QAT fail because the platform didn't supply the >> information required to make it work would be a nice loop. I don't >> want to completely paper over the problem without providing some other >> kind of feedback at the same time. > Okay -- I see what you're after here and I completely agree with it. But > sometimes I feel like I banging on a silent drum with some of these companies > about this stuff :( My frustration with these companies is starting to show I > guess... Just how visible is the QAT driver load failure? I has a similar issue with DCA not being configured in a number of BIOSes and it wasn't until I made the issue painfully visible with TAINT_FIRMWARE_WORKAROUND that I started to see any traction on getting this fixed in the BIOSes. We would need to sort out the systems that actually have bad BIOSes versus just being configured without PCI slots directly associated with any given NUMA node since there are systems where that is a valid configuration. >> You're probably aware of [1], which was the same problem. Apparently >> it was originally reported to RedHat as [2] (which is private, so I >> can't read it). That led to a workaround hack for some AMD systems >> [3, 4]. > Yeah ... part of me was thinking that maybe I should do something like > the above but I didn't know how you'd feel about expanding that hack. I'll look > into it. I'd prefer it to be opt-in with a kernel parameter. > > P. Are you thinking something like a "pci=assign-numa"? The problem is there doesn't seem to be a good way to currently determine the NUMA layout without the information being provided by the BIOS/ACPI tables, and we probably don't want to be creating a definition of the NUMA layout per platform. Thanks, Alex -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 10/16/2014 10:44 AM, Alexander Duyck wrote: > > On 10/16/2014 05:32 AM, Prarit Bhargava wrote: >> On 10/15/2014 05:20 PM, Bjorn Helgaas wrote: >>> On Wed, Oct 15, 2014 at 1:47 PM, Prarit Bhargava <prarit@redhat.com> wrote: >>>> On 10/15/2014 03:23 PM, Bjorn Helgaas wrote: >>>>> Hi Prarit, >>>>> >>>>> On Wed, Oct 15, 2014 at 1:05 PM, Prarit Bhargava <prarit@redhat.com> wrote: >>>>>> Consider a multi-node, multiple pci root bridge system which can be >>>>>> configured into one large node or one node/socket. When configuring the >>>>>> system the numa_node value for each PCI root bridge is always set >>>>>> incorrectly to -1, or NUMA_NO_NODE, rather than to the node value of each >>>>>> socket. Each PCI device inherits the numa value directly from it's parent >>>>>> device, so that the NUMA_NO_NODE value is passed through the entire PCI >>>>>> tree. >>>>>> >>>>>> Some new drivers, such as the Intel QAT driver, drivers/crypto/qat, >>>>>> require that a specific node be assigned to the device in order to >>>>>> achieve maximum performance for the device, and will fail to load if the >>>>>> device has NUMA_NO_NODE. >>>>> It seems ... unfriendly for a driver to fail to load just because it >>>>> can't guarantee maximum performance. Out of curiosity, where does >>>>> this actually happen? I had a quick look for NUMA_NO_NODE and >>>>> module_init() functions in drivers/crypto/qat, and I didn't see the >>>>> spot. >>>> The whole point of the Intel QAT driver is to guarantee max performance. If >>>> that is not possible the driver should not load (according to the thread >>>> mentioned below) > > This is just short-sighted thinking. The fact that the PCI device advertises -1 > means that either the BIOS isn't configured, or the PCI slots are shared as was > the case on some Nehalem systems where the IOH was shared between two sockets. Yes ... > I suspect that this driver doesn't even take that into account as it was likely > only written for Sandy Bridge architectures. > Nope. New hardware. The issue is that there is only a performance impact if local node memory is used, o/w the claim is that the performance drops to that of doing software crypto. >>>>>> To use this, one can do >>>>>> >>>>>> echo 3 > /sys/devices/pci0000:ff/0000:ff:1f.3/numa_node >>>>>> >>>>>> to set the numa node for PCI device 0000:ff:1f.3. >>>>> It definitely seems wrong that we don't set the node number correctly. >>>>> pci_acpi_scan_root() sets the node number by looking for a _PXM method >>>>> that applies to the host bridge. Why does that not work in this case? >>>>> Does the BIOS not supply _PXM? >>>> Yeah ... unfortunately the BIOS is broken in this case. And I know what you're >>>> thinking ;) -- why not get the BIOS fixed? I'm through relying on BIOS fixes >>>> which can take six months to a year to appear in a production version... I've >>>> been bitten too many times by promises of BIOS fixes that never materialize. >>> Yep, I understand. The question is how we implement a workaround so >>> it doesn't become the accepted way to do things. Obviously we don't >>> want people manually grubbing through numactl/lspci output or writing >>> shell scripts to do things that *should* happen automatically. > > I'd say if nothing else we should flag the system as tainted as soon as we start > overwriting BIOS/ACPI configured values with sysfs. This is one of the reasons > for the TAINT_FIRMWARE_WORKAROUND even existing. > I was thinking that I could modify the patch to do this, but I'd rather investigate Bjorn's suggestion first. I think his approach has some merits, but I will definitely TAINT if I go with that approach too. >>> Somewhere in the picture there needs to be a feedback loop that >>> encourages the vendor to fix the problem. I don't see that happening >>> yet. Having QAT fail because the platform didn't supply the >>> information required to make it work would be a nice loop. I don't >>> want to completely paper over the problem without providing some other >>> kind of feedback at the same time. >> Okay -- I see what you're after here and I completely agree with it. But >> sometimes I feel like I banging on a silent drum with some of these companies >> about this stuff :( My frustration with these companies is starting to show I >> guess... > > Just how visible is the QAT driver load failure? I has a similar issue with DCA > not being configured in a number of BIOSes and it wasn't until I made the issue > painfully visible with TAINT_FIRMWARE_WORKAROUND that I started to see any > traction on getting this fixed in the BIOSes. > Just a couple of printks to the screen. > We would need to sort out the systems that actually have bad BIOSes versus just > being configured without PCI slots directly associated with any given NUMA node > since there are systems where that is a valid configuration. The problem is NUMA_NO_NODE, which as you point out can be a valid configuration. So in some cases system designers may have intentionally done this (Can anyone think of a valid reason to leave off the _PXM, or have it assigned to NUMA_NO_NODE?), so the previous statement about having an opt-in, then attempting to calculate the node location, and now TAINTING might be a good direction to move in. OTOH ... what do we do about older unsupported hardware that won't have new BIOS releases? Those would basically say "Go fix your BIOS" and there's nothing that could be done :/. All those users see is a loud warning... > >>> You're probably aware of [1], which was the same problem. Apparently >>> it was originally reported to RedHat as [2] (which is private, so I >>> can't read it). That led to a workaround hack for some AMD systems >>> [3, 4]. >> Yeah ... part of me was thinking that maybe I should do something like >> the above but I didn't know how you'd feel about expanding that hack. I'll look >> into it. I'd prefer it to be opt-in with a kernel parameter. >> >> P. > > Are you thinking something like a "pci=assign-numa"? The problem is there > doesn't seem to be a good way to currently determine the NUMA layout without the > information being provided by the BIOS/ACPI tables, and we probably don't want > to be creating a definition of the NUMA layout per platform. Well ... let me think about this for a bit. The big issue is what happens during socket hot-add events and the PCI root bridges that are added at that time. It may not be possible to come up with a correct calculation :( but let me give it a shot. IIRC the node-to-socket map should be static... P. > > Thanks, > > Alex > > > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 10/16/2014 09:07 AM, Prarit Bhargava wrote: > On 10/16/2014 10:44 AM, Alexander Duyck wrote: >> On 10/16/2014 05:32 AM, Prarit Bhargava wrote: >>> On 10/15/2014 05:20 PM, Bjorn Helgaas wrote: >>>> On Wed, Oct 15, 2014 at 1:47 PM, Prarit Bhargava <prarit@redhat.com> wrote: >>>>> On 10/15/2014 03:23 PM, Bjorn Helgaas wrote: >>>>>> Hi Prarit, >>>>>> >>>>>> On Wed, Oct 15, 2014 at 1:05 PM, Prarit Bhargava <prarit@redhat.com> wrote: >>>>>>> Consider a multi-node, multiple pci root bridge system which can be >>>>>>> configured into one large node or one node/socket. When configuring the >>>>>>> system the numa_node value for each PCI root bridge is always set >>>>>>> incorrectly to -1, or NUMA_NO_NODE, rather than to the node value of each >>>>>>> socket. Each PCI device inherits the numa value directly from it's parent >>>>>>> device, so that the NUMA_NO_NODE value is passed through the entire PCI >>>>>>> tree. >>>>>>> >>>>>>> Some new drivers, such as the Intel QAT driver, drivers/crypto/qat, >>>>>>> require that a specific node be assigned to the device in order to >>>>>>> achieve maximum performance for the device, and will fail to load if the >>>>>>> device has NUMA_NO_NODE. >>>>>> It seems ... unfriendly for a driver to fail to load just because it >>>>>> can't guarantee maximum performance. Out of curiosity, where does >>>>>> this actually happen? I had a quick look for NUMA_NO_NODE and >>>>>> module_init() functions in drivers/crypto/qat, and I didn't see the >>>>>> spot. >>>>> The whole point of the Intel QAT driver is to guarantee max performance. If >>>>> that is not possible the driver should not load (according to the thread >>>>> mentioned below) >> This is just short-sighted thinking. The fact that the PCI device advertises -1 >> means that either the BIOS isn't configured, or the PCI slots are shared as was >> the case on some Nehalem systems where the IOH was shared between two sockets. > Yes ... > >> I suspect that this driver doesn't even take that into account as it was likely >> only written for Sandy Bridge architectures. >> > Nope. New hardware. The issue is that there is only a performance impact if > local node memory is used, o/w the claim is that the performance drops to that > of doing software crypto. Yes, but the problem is what is considered a local node? In the case of the Nehalem architecture it wasn't uncommon to have two sockets share an IOH. As a result each node would have its own memory, but the PCI devices were shared. That platform would fail this test, but each node has its own memory and I suspect the QPI overhead wouldn't be that bad since the link is dedicated to the IOH connection. What I am getting at is that this driver was likely intended for specifically the current and follow-on generations of Xeon processors. As such it deciding to reject all NUMA_NO_NODE configuration may be acceptable for it since they have a very specific architecture and CPU in mind. For the workaround if you are going to try and do something as generic, you will need to be mindful of how the other architectures deal with NUMA and PCI. >>>>>>> To use this, one can do >>>>>>> >>>>>>> echo 3 > /sys/devices/pci0000:ff/0000:ff:1f.3/numa_node >>>>>>> >>>>>>> to set the numa node for PCI device 0000:ff:1f.3. >>>>>> It definitely seems wrong that we don't set the node number correctly. >>>>>> pci_acpi_scan_root() sets the node number by looking for a _PXM method >>>>>> that applies to the host bridge. Why does that not work in this case? >>>>>> Does the BIOS not supply _PXM? >>>>> Yeah ... unfortunately the BIOS is broken in this case. And I know what you're >>>>> thinking ;) -- why not get the BIOS fixed? I'm through relying on BIOS fixes >>>>> which can take six months to a year to appear in a production version... I've >>>>> been bitten too many times by promises of BIOS fixes that never materialize. >>>> Yep, I understand. The question is how we implement a workaround so >>>> it doesn't become the accepted way to do things. Obviously we don't >>>> want people manually grubbing through numactl/lspci output or writing >>>> shell scripts to do things that *should* happen automatically. >> I'd say if nothing else we should flag the system as tainted as soon as we start >> overwriting BIOS/ACPI configured values with sysfs. This is one of the reasons >> for the TAINT_FIRMWARE_WORKAROUND even existing. >> > I was thinking that I could modify the patch to do this, but I'd rather > investigate Bjorn's suggestion first. I think his approach has some merits, but > I will definitely TAINT if I go with that approach too. If we are doing any sort of workaround we should mark the system as being tainted. Otherwise we are just going to let whatever workaround you implement be accepted and nobody will ever bother to fix the BIOS in this generation or the next. >>>> Somewhere in the picture there needs to be a feedback loop that >>>> encourages the vendor to fix the problem. I don't see that happening >>>> yet. Having QAT fail because the platform didn't supply the >>>> information required to make it work would be a nice loop. I don't >>>> want to completely paper over the problem without providing some other >>>> kind of feedback at the same time. >>> Okay -- I see what you're after here and I completely agree with it. But >>> sometimes I feel like I banging on a silent drum with some of these companies >>> about this stuff :( My frustration with these companies is starting to show I >>> guess... >> Just how visible is the QAT driver load failure? I has a similar issue with DCA >> not being configured in a number of BIOSes and it wasn't until I made the issue >> painfully visible with TAINT_FIRMWARE_WORKAROUND that I started to see any >> traction on getting this fixed in the BIOSes. >> > Just a couple of printks to the screen. Yeah, taint would definitely be preferred. Then if something has a panic later because we didn't work around this correctly we should be able to see that this is a tainted system in the panic dump. I did the same thing for DSA. >> We would need to sort out the systems that actually have bad BIOSes versus just >> being configured without PCI slots directly associated with any given NUMA node >> since there are systems where that is a valid configuration. > The problem is NUMA_NO_NODE, which as you point out can be a valid > configuration. So in some cases system designers may have intentionally done > this (Can anyone think of a valid reason to leave off the _PXM, or have it > assigned to NUMA_NO_NODE?), so the previous statement about having an opt-in, > then attempting to calculate the node location, and now TAINTING might be a good > direction to move in. That is my thought. We would just need to come up with a good way of sorting these platforms out and that can be the challenge. From past experience I have even seen some systems where the memory layout wasn't configured correctly in the BIOS/ACPI tables so this is pretty much just a crapshoot as to if we can figure out the actual layout or not via software. Maybe this could be identified with TAINT_OVERRIDDEN_ACPI_TABLE since we are having to hand code an ACPI table. > OTOH ... what do we do about older unsupported hardware that won't have new BIOS > releases? Those would basically say "Go fix your BIOS" and there's nothing that > could be done :/. All those users see is a loud warning... I'm not saying we cannot provide a workaround for it, but at the same time as you have pointed out this is mostly just a performance issue due to the BIOS and we could be introducing new issues by trying to fix it in the kernel. The loud warning is both for the users and those of us that are stuck debugging the issues they find when their platform doesn't run as expected and triggers a panic. You have to keep in mind that by working around things we run the risk of introducing new issues and we have to know when we have entered one of those cases. >>>> You're probably aware of [1], which was the same problem. Apparently >>>> it was originally reported to RedHat as [2] (which is private, so I >>>> can't read it). That led to a workaround hack for some AMD systems >>>> [3, 4]. >>> Yeah ... part of me was thinking that maybe I should do something like >>> the above but I didn't know how you'd feel about expanding that hack. I'll look >>> into it. I'd prefer it to be opt-in with a kernel parameter. >>> >>> P. >> Are you thinking something like a "pci=assign-numa"? The problem is there >> doesn't seem to be a good way to currently determine the NUMA layout without the >> information being provided by the BIOS/ACPI tables, and we probably don't want >> to be creating a definition of the NUMA layout per platform. > Well ... let me think about this for a bit. The big issue is what happens > during socket hot-add events and the PCI root bridges that are added at that > time. It may not be possible to come up with a correct calculation :( but let > me give it a shot. IIRC the node-to-socket map should be static... > > P. I don't know if there is a good way to resolve all this programmatically since I have seen a number of issues where even the NUMA memory layout is messed up. The sysfs might be a good approach however I would suggest tainting the kernel at that point as you are overwritting pre-defined BIOS/ACPI table values and that may have certain side effects if things don't get configured correctly. Thanks, Alex -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, 2014-10-16 at 08:32 -0400, Prarit Bhargava wrote: > > On 10/15/2014 05:20 PM, Bjorn Helgaas wrote: > > On Wed, Oct 15, 2014 at 1:47 PM, Prarit Bhargava <prarit@redhat.com> wrote: > >> On 10/15/2014 03:23 PM, Bjorn Helgaas wrote: > >>> Hi Prarit, > >>> > >>> On Wed, Oct 15, 2014 at 1:05 PM, Prarit Bhargava <prarit@redhat.com> wrote: > >>>> Consider a multi-node, multiple pci root bridge system which can be > >>>> configured into one large node or one node/socket. When configuring the > >>>> system the numa_node value for each PCI root bridge is always set > >>>> incorrectly to -1, or NUMA_NO_NODE, rather than to the node value of each > >>>> socket. Each PCI device inherits the numa value directly from it's parent > >>>> device, so that the NUMA_NO_NODE value is passed through the entire PCI > >>>> tree. > >>>> > >>>> Some new drivers, such as the Intel QAT driver, drivers/crypto/qat, > >>>> require that a specific node be assigned to the device in order to > >>>> achieve maximum performance for the device, and will fail to load if the > >>>> device has NUMA_NO_NODE. > >>> > >>> It seems ... unfriendly for a driver to fail to load just because it > >>> can't guarantee maximum performance. Out of curiosity, where does > >>> this actually happen? I had a quick look for NUMA_NO_NODE and > >>> module_init() functions in drivers/crypto/qat, and I didn't see the > >>> spot. > >> > >> The whole point of the Intel QAT driver is to guarantee max performance. If > >> that is not possible the driver should not load (according to the thread > >> mentioned below) > >> > >>> > >>>> The driver would load if the numa_node value > >>>> was equal to or greater than -1 and quickly hacking the driver results in > >>>> a functional QAT driver. > >>>> > >>>> Using lspci and numactl it is easy to determine what the numa value should > >>>> be. The problem is that there is no way to set it. This patch adds a > >>>> store function for the PCI device's numa_node value. > >>> > >>> I'm not familiar with numactl. It sounds like it can show you the > >>> NUMA topology? Where does that information come from? > >> > >> You can map at least what nodes are available (although I suppose you can get > >> the same information from dmesg). You have to do a bit of hunting through the > >> PCI tree to determine the root PCI devices, but you can determine which root > >> device is connected to which node. > > > > Is numactl reading SRAT? SLIT? SMBIOS tables? Presumably the kernel > > has access to whatever information you're getting from numactl and > > lspci, and if so, maybe we can do the workaround automatically in the > > kernel. > > I'll go figure that out ... > > > > >>>> To use this, one can do > >>>> > >>>> echo 3 > /sys/devices/pci0000:ff/0000:ff:1f.3/numa_node > >>>> > >>>> to set the numa node for PCI device 0000:ff:1f.3. > >>> > >>> It definitely seems wrong that we don't set the node number correctly. > >>> pci_acpi_scan_root() sets the node number by looking for a _PXM method > >>> that applies to the host bridge. Why does that not work in this case? > >>> Does the BIOS not supply _PXM? > >> > >> Yeah ... unfortunately the BIOS is broken in this case. And I know what you're > >> thinking ;) -- why not get the BIOS fixed? I'm through relying on BIOS fixes > >> which can take six months to a year to appear in a production version... I've > >> been bitten too many times by promises of BIOS fixes that never materialize. > > > > Yep, I understand. The question is how we implement a workaround so > > it doesn't become the accepted way to do things. Obviously we don't > > want people manually grubbing through numactl/lspci output or writing > > shell scripts to do things that *should* happen automatically. > > > >> We have systems that only have a support cycle of 3 years, and things like ACPI > >> _PXM updates are at the bottom of the list :/. > > > > > > > Somewhere in the picture there needs to be a feedback loop that > > encourages the vendor to fix the problem. I don't see that happening > > yet. Having QAT fail because the platform didn't supply the > > information required to make it work would be a nice loop. I don't > > want to completely paper over the problem without providing some other > > kind of feedback at the same time. > > Okay -- I see what you're after here and I completely agree with it. But > sometimes I feel like I banging on a silent drum with some of these companies > about this stuff :( My frustration with these companies is starting to show I > guess... > > > > > You're probably aware of [1], which was the same problem. Apparently > > it was originally reported to RedHat as [2] (which is private, so I > > can't read it). That led to a workaround hack for some AMD systems > > [3, 4]. > > Yeah ... part of me was thinking that maybe I should do something like > the above but I didn't know how you'd feel about expanding that hack. I'll look > into it. I'd prefer it to be opt-in with a kernel parameter. I believe the point was to not consider expanding upon the AMD chip-set specific driver, or some similar tactic, and to investigate how 'numactl' obtains such information in order to see if that is a possible solution that could be used going forward. It's good to see that the latest discussions with Alexander seem to suggest that is the direction being taken now. Pursuing something like the AMD scenario, where a chip-set specific driver reads internal registers, is an untenable dead end. It leads to a perpetual cycle in which the driver has to constantly be updated as new platform chip-sets are introduced. To solve such situations, architecture independent mechanisms are thought up, formalized, and put in place - in this case ACPI's _PXM methods and/or SRAT, SLIT tables. Chip-set specific drivers like 'amd_bus.c' perpetuate circumventing architected solutions, more often than not introducing subsequent issues themselves. The previous NUMA info issue that Bjorn referenced is a prime example of both: it "snoops" out proximity info from the chip-set when the BIOS has not supplied ACPI _PXM method(s) (i.e. the circumvention) and in doing such, had at least three sub-issues; all of which can be understood by carefully reading the chain of events from the PCI list's thread [1]. As a result, the 'amd_bus.c' patch was pared down from a substantial re-factoring and update effort to its bare minimum - at one point there was even discussion about removing the driver completely as was done with 'intel_bus.c' (note that the NUMA related proximity "snooping" capability only exists for AMD based platforms, there is no equivalent for Intel based platforms). In that particular instance the end result was that the customer impact was significant enough financially that it forced the vendor to updated there BIOS to include the necessary _PXM methods. Introducing kernel parameters is a similar scenario. Customers should not need to know about, nor utilize, kernel parameters in their normal day-to-day activities. Yes, such capabilities are invaluable for those of us that work with the kernel but customers just should not be expected to have to resort to such. [1] https://lkml.org/lkml/2014/3/5/898 Myron > > P. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 10/16/2014 03:45 PM, Myron Stowe wrote: > On Thu, 2014-10-16 at 08:32 -0400, Prarit Bhargava wrote: >> >> On 10/15/2014 05:20 PM, Bjorn Helgaas wrote: >>> On Wed, Oct 15, 2014 at 1:47 PM, Prarit Bhargava <prarit@redhat.com> wrote: >>>> On 10/15/2014 03:23 PM, Bjorn Helgaas wrote: >>>>> Hi Prarit, >>>>> >>>>> On Wed, Oct 15, 2014 at 1:05 PM, Prarit Bhargava <prarit@redhat.com> wrote: >>>>>> Consider a multi-node, multiple pci root bridge system which can be >>>>>> configured into one large node or one node/socket. When configuring the >>>>>> system the numa_node value for each PCI root bridge is always set >>>>>> incorrectly to -1, or NUMA_NO_NODE, rather than to the node value of each >>>>>> socket. Each PCI device inherits the numa value directly from it's parent >>>>>> device, so that the NUMA_NO_NODE value is passed through the entire PCI >>>>>> tree. >>>>>> >>>>>> Some new drivers, such as the Intel QAT driver, drivers/crypto/qat, >>>>>> require that a specific node be assigned to the device in order to >>>>>> achieve maximum performance for the device, and will fail to load if the >>>>>> device has NUMA_NO_NODE. >>>>> >>>>> It seems ... unfriendly for a driver to fail to load just because it >>>>> can't guarantee maximum performance. Out of curiosity, where does >>>>> this actually happen? I had a quick look for NUMA_NO_NODE and >>>>> module_init() functions in drivers/crypto/qat, and I didn't see the >>>>> spot. >>>> >>>> The whole point of the Intel QAT driver is to guarantee max performance. If >>>> that is not possible the driver should not load (according to the thread >>>> mentioned below) >>>> >>>>> >>>>>> The driver would load if the numa_node value >>>>>> was equal to or greater than -1 and quickly hacking the driver results in >>>>>> a functional QAT driver. >>>>>> >>>>>> Using lspci and numactl it is easy to determine what the numa value should >>>>>> be. The problem is that there is no way to set it. This patch adds a >>>>>> store function for the PCI device's numa_node value. >>>>> >>>>> I'm not familiar with numactl. It sounds like it can show you the >>>>> NUMA topology? Where does that information come from? numactl simply determines the number of nodes on the system by traversing /sys/devices/system/node For example, the output of 'numactl --hardware' available: 2 nodes (0-1) node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 24 25 26 27 28 29 30 31 32 33 34 35 node 0 size: 32075 MB node 0 free: 30862 MB node 1 cpus: 12 13 14 15 16 17 18 19 20 21 22 23 36 37 38 39 40 41 42 43 44 45 46 47 node 1 size: 32239 MB node 1 free: 31251 MB node distances: node 0 1 0: 10 21 1: 21 10 I then use lpsci to determine what pci root nodes there are, and knowing a little bit about the system architecture (are the IOHs shared between sockets, are they 1/socket, etc.) I can make an educated guess on what the numa_node value should be. I thought about hardcoding something similar in the kernel ... but there are some significant issues (which Myron points out as well). The code would have to be constantly maintained. That is not something we can do long term. Every new processor & chipset would have to be added to the code to determine exactly how the pci root bridge was connected. Even then, it is entirely possible (as in the case with some cpu hotplug systems) that IOH-less sockets were populated [1] which would severely hamper any assumptions in a calculation. That also doesn't take into account systems where the manufacturer *wants* NUMA_NO_NODE, and doesn't want per-node allocations. Alexander has suggested that modifying my original patch to do (sorry for the cut-and-paste) static ssize_t numa_node_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { int node, ret; if (!capable(CAP_SYS_ADMIN)) return -EPERM; ret = kstrtoint(buf, 0, &node); if (ret) return ret; if (!node_online(node)) return -EINVAL; WARN_TAINT(1, TAINT_FIRMWARE_WORKAROUND, FW_BUG "ACPI _PXM should have set this device's root bridge numa_node to %d but set it to %d. Please contact your hardware vendor for updates.", node, dev->numa_node); dev->numa_node = node; return count; } *might* be amenable to everyone. I think it nicely handles Bjorn's concern about being loud when overriding the _PXM entries ... P. [1] These sockets really aren't IOH-less. The IOH has been disabled in BIOS. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 2014/10/17 19:59, Prarit Bhargava wrote: > > > On 10/16/2014 03:45 PM, Myron Stowe wrote: >> On Thu, 2014-10-16 at 08:32 -0400, Prarit Bhargava wrote: >>> >>> On 10/15/2014 05:20 PM, Bjorn Helgaas wrote: >>>> On Wed, Oct 15, 2014 at 1:47 PM, Prarit Bhargava <prarit@redhat.com> wrote: >>>>> On 10/15/2014 03:23 PM, Bjorn Helgaas wrote: >>>>>> Hi Prarit, >>>>>> >>>>>> On Wed, Oct 15, 2014 at 1:05 PM, Prarit Bhargava <prarit@redhat.com> wrote: >>>>>>> Consider a multi-node, multiple pci root bridge system which can be >>>>>>> configured into one large node or one node/socket. When configuring the >>>>>>> system the numa_node value for each PCI root bridge is always set >>>>>>> incorrectly to -1, or NUMA_NO_NODE, rather than to the node value of each >>>>>>> socket. Each PCI device inherits the numa value directly from it's parent >>>>>>> device, so that the NUMA_NO_NODE value is passed through the entire PCI >>>>>>> tree. >>>>>>> >>>>>>> Some new drivers, such as the Intel QAT driver, drivers/crypto/qat, >>>>>>> require that a specific node be assigned to the device in order to >>>>>>> achieve maximum performance for the device, and will fail to load if the >>>>>>> device has NUMA_NO_NODE. >>>>>> >>>>>> It seems ... unfriendly for a driver to fail to load just because it >>>>>> can't guarantee maximum performance. Out of curiosity, where does >>>>>> this actually happen? I had a quick look for NUMA_NO_NODE and >>>>>> module_init() functions in drivers/crypto/qat, and I didn't see the >>>>>> spot. >>>>> >>>>> The whole point of the Intel QAT driver is to guarantee max performance. If >>>>> that is not possible the driver should not load (according to the thread >>>>> mentioned below) >>>>> >>>>>> >>>>>>> The driver would load if the numa_node value >>>>>>> was equal to or greater than -1 and quickly hacking the driver results in >>>>>>> a functional QAT driver. >>>>>>> >>>>>>> Using lspci and numactl it is easy to determine what the numa value should >>>>>>> be. The problem is that there is no way to set it. This patch adds a >>>>>>> store function for the PCI device's numa_node value. >>>>>> >>>>>> I'm not familiar with numactl. It sounds like it can show you the >>>>>> NUMA topology? Where does that information come from? > > numactl simply determines the number of nodes on the system by traversing > > /sys/devices/system/node > > For example, the output of 'numactl --hardware' > > available: 2 nodes (0-1) > node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 24 25 26 27 28 29 30 31 32 33 34 35 > node 0 size: 32075 MB > node 0 free: 30862 MB > node 1 cpus: 12 13 14 15 16 17 18 19 20 21 22 23 36 37 38 39 40 41 42 43 44 45 46 47 > node 1 size: 32239 MB > node 1 free: 31251 MB > node distances: > node 0 1 > 0: 10 21 > 1: 21 10 > > I then use lpsci to determine what pci root nodes there are, and knowing a > little bit about the system architecture (are the IOHs shared between sockets, > are they 1/socket, etc.) I can make an educated guess on what the numa_node > value should be. Hi Prarit, It may be a little hard for normal users to figure out NUMA node id from [segment:bus]. [segment:bus] for PCIe host bridge are under control of BIOS/firmware. For example, one a four socket system, I have observed one vender putting all four PCIe host brdiges into PCI segment 0, another vender assigning different segment for each PCIe host bridge. And socket hotplug may also make the scenario more complex. Actually I ran into the same issue when trying to optimize interrupt vector allocation according to NUMA affinity. So it will be great if we could find an acceptable solution here:) Regard! Gerry > > I thought about hardcoding something similar in the kernel ... but there are > some significant issues (which Myron points out as well). The code would have > to be constantly maintained. That is not something we can do long term. Every > new processor & chipset would have to be added to the code to determine exactly > how the pci root bridge was connected. Even then, it is entirely possible (as > in the case with some cpu hotplug systems) that IOH-less sockets were populated > [1] which would severely hamper any assumptions in a calculation. > > That also doesn't take into account systems where the manufacturer *wants* > NUMA_NO_NODE, and doesn't want per-node allocations. > > Alexander has suggested that modifying my original patch to do (sorry for the > cut-and-paste) > > static ssize_t numa_node_store(struct device *dev, > struct device_attribute *attr, > const char *buf, size_t count) > { > int node, ret; > > if (!capable(CAP_SYS_ADMIN)) > return -EPERM; > > ret = kstrtoint(buf, 0, &node); > if (ret) > return ret; > > if (!node_online(node)) > return -EINVAL; > > WARN_TAINT(1, TAINT_FIRMWARE_WORKAROUND, > FW_BUG "ACPI _PXM should have set this device's root bridge > numa_node to %d but set it to %d. Please contact your hardware vendor for > updates.", > node, dev->numa_node); > > dev->numa_node = node; > > return count; > } > > *might* be amenable to everyone. I think it nicely handles Bjorn's concern > about being loud when overriding the _PXM entries ... > > P. > > [1] These sockets really aren't IOH-less. The IOH has been disabled in BIOS. > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index 92b6d9a..c05ed30 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -221,12 +221,33 @@ static ssize_t enabled_show(struct device *dev, struct device_attribute *attr, static DEVICE_ATTR_RW(enabled); #ifdef CONFIG_NUMA +static ssize_t numa_node_store(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t count) +{ + int node, ret; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + ret = kstrtoint(buf, 0, &node); + if (ret) + return ret; + + if (!node_online(node)) + return -EINVAL; + + dev->numa_node = node; + + return count; +} + static ssize_t numa_node_show(struct device *dev, struct device_attribute *attr, char *buf) { return sprintf(buf, "%d\n", dev->numa_node); } -static DEVICE_ATTR_RO(numa_node); +static DEVICE_ATTR_RW(numa_node); #endif static ssize_t dma_mask_bits_show(struct device *dev,
Consider a multi-node, multiple pci root bridge system which can be configured into one large node or one node/socket. When configuring the system the numa_node value for each PCI root bridge is always set incorrectly to -1, or NUMA_NO_NODE, rather than to the node value of each socket. Each PCI device inherits the numa value directly from it's parent device, so that the NUMA_NO_NODE value is passed through the entire PCI tree. Some new drivers, such as the Intel QAT driver, drivers/crypto/qat, require that a specific node be assigned to the device in order to achieve maximum performance for the device, and will fail to load if the device has NUMA_NO_NODE. The driver would load if the numa_node value was equal to or greater than -1 and quickly hacking the driver results in a functional QAT driver. Using lspci and numactl it is easy to determine what the numa value should be. The problem is that there is no way to set it. This patch adds a store function for the PCI device's numa_node value. To use this, one can do echo 3 > /sys/devices/pci0000:ff/0000:ff:1f.3/numa_node to set the numa node for PCI device 0000:ff:1f.3. Cc: Myron Stowe <mstowe@redhat.com> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: linux-pci@vger.kernel.org Signed-off-by: Prarit Bhargava <prarit@redhat.com> --- drivers/pci/pci-sysfs.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-)