| Message ID | 1367971156.30363.32.camel@misato.fc.hp.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
On Tuesday, May 07, 2013 05:59:16 PM Toshi Kani wrote: > On Wed, 2013-05-08 at 01:17 +0200, Rafael J. Wysocki wrote: > > On Tuesday, May 07, 2013 04:45:40 PM Toshi Kani wrote: > > > On Wed, 2013-05-08 at 00:10 +0200, Rafael J. Wysocki wrote: > > > > On Tuesday, May 07, 2013 03:03:49 PM Toshi Kani wrote: > > > > > On Tue, 2013-05-07 at 14:11 +0200, Rafael J. Wysocki wrote: > > > > > > On Tuesday, May 07, 2013 12:59:45 PM Vasilis Liaskovitis wrote: > > > > > > > > > > : > > > > > > > > > > > Updated patch is appended for completness. > > > > > > > > > > Yes, this updated patch solved the locking issue. > > > > > > > > > > > > > > A more general issue is that there are now two memory offlining efforts: > > > > > > > > > > > > > > > > > > 1) from acpi_bus_offline_companions during device offline > > > > > > > > > 2) from mm: remove_memory during device detach (offline_memory_block_cb) > > > > > > > > > > > > > > > > > > The 2nd is only called if the device offline operation was already succesful, so > > > > > > > > > it seems ineffective or redundant now, at least for x86_64/acpi_memhotplug machine > > > > > > > > > (unless the blocks were re-onlined in between). > > > > > > > > > > > > > > > > Sure, and that should be OK for now. Changing the detach behavior is not > > > > > > > > essential from the patch [2/2] perspective, we can do it later. > > > > > > > > > > > > > > yes, ok. > > > > > > > > > > > > > > > > > > > > > > > > On the other hand, the 2nd effort has some more intelligence in offlining, as it > > > > > > > > > tries to offline twice in the precense of memcg, see commits df3e1b91 or > > > > > > > > > reworked 0baeab16. Maybe we need to consolidate the logic. > > > > > > > > > > > > > > > > Hmm. Perhaps it would make sense to implement that logic in > > > > > > > > memory_subsys_offline(), then? > > > > > > > > > > > > > > the logic tries to offline the memory blocks of the device twice, because the > > > > > > > first memory block might be storing information for the subsequent memblocks. > > > > > > > > > > > > > > memory_subsys_offline operates on one memory block at a time. Perhaps we can get > > > > > > > the same effect if we do an acpi_walk of acpi_bus_offline_companions twice in > > > > > > > acpi_scan_hot_remove but it's probably not a good idea, since that would > > > > > > > affect non-memory devices as well. > > > > > > > > > > > > > > I am not sure how important this intelligence is in practice (I am not using > > > > > > > mem cgroups in my guest kernel tests yet). Maybe Wen (original author) has > > > > > > > more details on 2-pass offlining effectiveness. > > > > > > > > > > > > OK > > > > > > > > > > > > It may be added in a separate patch in any case. > > > > > > > > > > I had the same comment as Vasilis. And, I agree with you that we can > > > > > enhance it in separate patches. > > > > > > > > > > : > > > > > > > > > > > +static int memory_subsys_offline(struct device *dev) > > > > > > +{ > > > > > > + struct memory_block *mem = container_of(dev, struct memory_block, dev); > > > > > > + int ret; > > > > > > + > > > > > > + mutex_lock(&mem->state_mutex); > > > > > > + ret = __memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE, -1); > > > > > > > > > > This function needs to check mem->state just like > > > > > offline_memory_block(). That is: > > > > > > > > > > int ret = 0; > > > > > : > > > > > if (mem->state != MEM_OFFLINE) > > > > > ret = __memory_block_change_state(...); > > > > > > > > > > Otherwise, memory hot-delete to an off-lined memory fails in > > > > > __memory_block_change_state() since mem->state is already set to > > > > > MEM_OFFLINE. > > > > > > > > > > With that change, for the series: > > > > > Reviewed-by: Toshi Kani <toshi.kani@hp.com> > > > > > > > > OK, one more update, then (appended). > > > > > > > > That said I thought that the check against dev->offline in device_offline() > > > > would be sufficient to guard agaist that. Is there any "offline" code path > > > > I didn't take into account? > > > > > > Oh, you are right about that. The real problem is that dev->offline is > > > set to false (0) when a new memory is hot-added in off-line state. So, > > > instead, dev->offline needs to be set properly. > > > > OK, where does that happen? > > It's a bit messy, but the following change seems to work. A tricky part > is that online() is not called during boot, so I needed to update the > offline flag in __memory_block_change_state(). I wonder why? -> > --- > drivers/base/memory.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/base/memory.c b/drivers/base/memory.c > index b9dfd34..1c8d781 100644 > --- a/drivers/base/memory.c > +++ b/drivers/base/memory.c > @@ -294,8 +294,10 @@ static int __memory_block_change_state(struct > memory_block *mem, > mem->state = from_state_req; > } else { > mem->state = to_state; > - if (to_state == MEM_ONLINE) > + if (to_state == MEM_ONLINE) { > mem->last_online = online_type; > + mem->dev.offline = false; > + } -> __memory_block_change_state() is called by memory_subsys_online/offline() and by __memory_block_change_state_uevent() only, so it should be sufficient to do this under the switch () in the latter. Still, though, __memory_block_change_state_uevent() is only called (indirectly) from store_mem_state() and by offline_memory_block() the both of which update dev->offline. What's the exact scenario you needed this for? > } > return ret; > } > @@ -613,6 +615,7 @@ static int init_memory_block(struct memory_block > **memory, > mem->state = state; > mem->last_online = ONLINE_KEEP; > mem->section_count++; > + mem->dev.offline = (state == MEM_OFFLINE) ? true : false; You could write this as + mem->dev.offline = state == MEM_OFFLINE; Moreover, it'd be better to do it in register_memory(), I think. > mutex_init(&mem->state_mutex); > start_pfn = section_nr_to_pfn(mem->start_section_nr); > mem->phys_device = arch_get_memory_phys_device(start_pfn); Thanks, Rafael
On Wed, 2013-05-08 at 02:24 +0200, Rafael J. Wysocki wrote: > On Tuesday, May 07, 2013 05:59:16 PM Toshi Kani wrote: > > On Wed, 2013-05-08 at 01:17 +0200, Rafael J. Wysocki wrote: > > > On Tuesday, May 07, 2013 04:45:40 PM Toshi Kani wrote: > > > > On Wed, 2013-05-08 at 00:10 +0200, Rafael J. Wysocki wrote: > > > > > On Tuesday, May 07, 2013 03:03:49 PM Toshi Kani wrote: > > > > > > On Tue, 2013-05-07 at 14:11 +0200, Rafael J. Wysocki wrote: > > > > > > > On Tuesday, May 07, 2013 12:59:45 PM Vasilis Liaskovitis wrote: > > > > > > > > > > > > : > > > > > > > > > > > > > Updated patch is appended for completness. > > > > > > > > > > > > Yes, this updated patch solved the locking issue. > > > > > > > > > > > > > > > > A more general issue is that there are now two memory offlining efforts: > > > > > > > > > > > > > > > > > > > > 1) from acpi_bus_offline_companions during device offline > > > > > > > > > > 2) from mm: remove_memory during device detach (offline_memory_block_cb) > > > > > > > > > > > > > > > > > > > > The 2nd is only called if the device offline operation was already succesful, so > > > > > > > > > > it seems ineffective or redundant now, at least for x86_64/acpi_memhotplug machine > > > > > > > > > > (unless the blocks were re-onlined in between). > > > > > > > > > > > > > > > > > > Sure, and that should be OK for now. Changing the detach behavior is not > > > > > > > > > essential from the patch [2/2] perspective, we can do it later. > > > > > > > > > > > > > > > > yes, ok. > > > > > > > > > > > > > > > > > > > > > > > > > > > On the other hand, the 2nd effort has some more intelligence in offlining, as it > > > > > > > > > > tries to offline twice in the precense of memcg, see commits df3e1b91 or > > > > > > > > > > reworked 0baeab16. Maybe we need to consolidate the logic. > > > > > > > > > > > > > > > > > > Hmm. Perhaps it would make sense to implement that logic in > > > > > > > > > memory_subsys_offline(), then? > > > > > > > > > > > > > > > > the logic tries to offline the memory blocks of the device twice, because the > > > > > > > > first memory block might be storing information for the subsequent memblocks. > > > > > > > > > > > > > > > > memory_subsys_offline operates on one memory block at a time. Perhaps we can get > > > > > > > > the same effect if we do an acpi_walk of acpi_bus_offline_companions twice in > > > > > > > > acpi_scan_hot_remove but it's probably not a good idea, since that would > > > > > > > > affect non-memory devices as well. > > > > > > > > > > > > > > > > I am not sure how important this intelligence is in practice (I am not using > > > > > > > > mem cgroups in my guest kernel tests yet). Maybe Wen (original author) has > > > > > > > > more details on 2-pass offlining effectiveness. > > > > > > > > > > > > > > OK > > > > > > > > > > > > > > It may be added in a separate patch in any case. > > > > > > > > > > > > I had the same comment as Vasilis. And, I agree with you that we can > > > > > > enhance it in separate patches. > > > > > > > > > > > > : > > > > > > > > > > > > > +static int memory_subsys_offline(struct device *dev) > > > > > > > +{ > > > > > > > + struct memory_block *mem = container_of(dev, struct memory_block, dev); > > > > > > > + int ret; > > > > > > > + > > > > > > > + mutex_lock(&mem->state_mutex); > > > > > > > + ret = __memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE, -1); > > > > > > > > > > > > This function needs to check mem->state just like > > > > > > offline_memory_block(). That is: > > > > > > > > > > > > int ret = 0; > > > > > > : > > > > > > if (mem->state != MEM_OFFLINE) > > > > > > ret = __memory_block_change_state(...); > > > > > > > > > > > > Otherwise, memory hot-delete to an off-lined memory fails in > > > > > > __memory_block_change_state() since mem->state is already set to > > > > > > MEM_OFFLINE. > > > > > > > > > > > > With that change, for the series: > > > > > > Reviewed-by: Toshi Kani <toshi.kani@hp.com> > > > > > > > > > > OK, one more update, then (appended). > > > > > > > > > > That said I thought that the check against dev->offline in device_offline() > > > > > would be sufficient to guard agaist that. Is there any "offline" code path > > > > > I didn't take into account? > > > > > > > > Oh, you are right about that. The real problem is that dev->offline is > > > > set to false (0) when a new memory is hot-added in off-line state. So, > > > > instead, dev->offline needs to be set properly. > > > > > > OK, where does that happen? > > > > It's a bit messy, but the following change seems to work. A tricky part > > is that online() is not called during boot, so I needed to update the > > offline flag in __memory_block_change_state(). > > I wonder why? -> > > > --- > > drivers/base/memory.c | 5 ++++- > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/base/memory.c b/drivers/base/memory.c > > index b9dfd34..1c8d781 100644 > > --- a/drivers/base/memory.c > > +++ b/drivers/base/memory.c > > @@ -294,8 +294,10 @@ static int __memory_block_change_state(struct > > memory_block *mem, > > mem->state = from_state_req; > > } else { > > mem->state = to_state; > > - if (to_state == MEM_ONLINE) > > + if (to_state == MEM_ONLINE) { > > mem->last_online = online_type; > > + mem->dev.offline = false; > > + } > > -> > > __memory_block_change_state() is called by memory_subsys_online/offline() > and by __memory_block_change_state_uevent() only, so it should be sufficient > to do this under the switch () in the latter. > > Still, though, __memory_block_change_state_uevent() is only called (indirectly) > from store_mem_state() and by offline_memory_block() the both of which update > dev->offline. > > What's the exact scenario you needed this for? Right. I was in hurry and made a wrong assumption... This change is not necessary. > > } > > return ret; > > } > > @@ -613,6 +615,7 @@ static int init_memory_block(struct memory_block > > **memory, > > mem->state = state; > > mem->last_online = ONLINE_KEEP; > > mem->section_count++; > > + mem->dev.offline = (state == MEM_OFFLINE) ? true : false; > > You could write this as > > + mem->dev.offline = state == MEM_OFFLINE; Right. > Moreover, it'd be better to do it in register_memory(), I think. Yes, if we change register_memory() to have the arg state. Thanks, -Toshi > > > mutex_init(&mem->state_mutex); > > start_pfn = section_nr_to_pfn(mem->start_section_nr); > > mem->phys_device = arch_get_memory_phys_device(start_pfn); > > Thanks, > Rafael > > -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" 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/base/memory.c b/drivers/base/memory.c index b9dfd34..1c8d781 100644 --- a/drivers/base/memory.c +++ b/drivers/base/memory.c @@ -294,8 +294,10 @@ static int __memory_block_change_state(struct memory_block *mem, mem->state = from_state_req; } else { mem->state = to_state; - if (to_state == MEM_ONLINE) + if (to_state == MEM_ONLINE) { mem->last_online = online_type; + mem->dev.offline = false; + } } return ret;