| Message ID | 20210726013806.84815-1-damien.lemoal@wdc.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Initial support for multi-actuator HDDs | expand |
On 2021/07/26 10:38, Damien Le Moal wrote: > Single LUN multi-actuator hard-disks are cappable to seek and execute > multiple commands in parallel. This capability is exposed to the host > using the Concurrent Positioning Ranges VPD page (SCSI) and Log (ATA). > Each positioning range describes the contiguous set of LBAs that an > actuator serves. > > This series adds support the scsi disk driver to retreive this > information and advertize it to user space through sysfs. libata is also > modified to handle ATA drives. > > The first patch adds the block layer plumbing to expose concurrent > sector ranges of the device through sysfs as a sub-directory of the > device sysfs queue directory. Patch 2 and 3 add support to sd and > libata. Finally patch 4 documents the sysfs queue attributed changes. > > This series does not attempt in any way to optimize accesses to > multi-actuator devices (e.g. block IO scheduler or filesystems). This > initial support only exposes the actuators information to user space > through sysfs. Jens, Martin, Any comment on this series ? > > Changes from v2: > * Update patch 1 to fix a compilation warning for a potential NULL > pointer dereference of the cr argument of blk_queue_set_cranges(). > Warning reported by the kernel test robot <lkp@intel.com>). > > Changes from v1: > * Moved libata-scsi hunk from patch 1 to patch 3 where it belongs > * Fixed unintialized variable in patch 2 > Reported-by: kernel test robot <lkp@intel.com> > Reported-by: Dan Carpenter <dan.carpenter@oracle.com > * Changed patch 3 adding struct ata_cpr_log to contain both the number > of concurrent ranges and the array of concurrent ranges. > * Added a note in the documentation (patch 4) about the unit used for > the concurrent ranges attributes. > > Damien Le Moal (4): > block: Add concurrent positioning ranges support > scsi: sd: add concurrent positioning ranges support > libata: support concurrent positioning ranges log > doc: document sysfs queue/cranges attributes > > Documentation/block/queue-sysfs.rst | 30 ++- > block/Makefile | 2 +- > block/blk-cranges.c | 295 ++++++++++++++++++++++++++++ > block/blk-sysfs.c | 13 ++ > block/blk.h | 3 + > drivers/ata/libata-core.c | 52 +++++ > drivers/ata/libata-scsi.c | 48 ++++- > drivers/scsi/sd.c | 81 ++++++++ > drivers/scsi/sd.h | 1 + > include/linux/ata.h | 1 + > include/linux/blkdev.h | 29 +++ > include/linux/libata.h | 15 ++ > 12 files changed, 559 insertions(+), 11 deletions(-) > create mode 100644 block/blk-cranges.c >
On 2021/07/26 10:38, Damien Le Moal wrote: > Single LUN multi-actuator hard-disks are cappable to seek and execute > multiple commands in parallel. This capability is exposed to the host > using the Concurrent Positioning Ranges VPD page (SCSI) and Log (ATA). > Each positioning range describes the contiguous set of LBAs that an > actuator serves. > > This series adds support the scsi disk driver to retreive this > information and advertize it to user space through sysfs. libata is also > modified to handle ATA drives. > > The first patch adds the block layer plumbing to expose concurrent > sector ranges of the device through sysfs as a sub-directory of the > device sysfs queue directory. Patch 2 and 3 add support to sd and > libata. Finally patch 4 documents the sysfs queue attributed changes. > > This series does not attempt in any way to optimize accesses to > multi-actuator devices (e.g. block IO scheduler or filesystems). This > initial support only exposes the actuators information to user space > through sysfs. Jens, Martin, re-ping... Any comment on this series ? > > Changes from v2: > * Update patch 1 to fix a compilation warning for a potential NULL > pointer dereference of the cr argument of blk_queue_set_cranges(). > Warning reported by the kernel test robot <lkp@intel.com>). > > Changes from v1: > * Moved libata-scsi hunk from patch 1 to patch 3 where it belongs > * Fixed unintialized variable in patch 2 > Reported-by: kernel test robot <lkp@intel.com> > Reported-by: Dan Carpenter <dan.carpenter@oracle.com > * Changed patch 3 adding struct ata_cpr_log to contain both the number > of concurrent ranges and the array of concurrent ranges. > * Added a note in the documentation (patch 4) about the unit used for > the concurrent ranges attributes. > > Damien Le Moal (4): > block: Add concurrent positioning ranges support > scsi: sd: add concurrent positioning ranges support > libata: support concurrent positioning ranges log > doc: document sysfs queue/cranges attributes > > Documentation/block/queue-sysfs.rst | 30 ++- > block/Makefile | 2 +- > block/blk-cranges.c | 295 ++++++++++++++++++++++++++++ > block/blk-sysfs.c | 13 ++ > block/blk.h | 3 + > drivers/ata/libata-core.c | 52 +++++ > drivers/ata/libata-scsi.c | 48 ++++- > drivers/scsi/sd.c | 81 ++++++++ > drivers/scsi/sd.h | 1 + > include/linux/ata.h | 1 + > include/linux/blkdev.h | 29 +++ > include/linux/libata.h | 15 ++ > 12 files changed, 559 insertions(+), 11 deletions(-) > create mode 100644 block/blk-cranges.c >
Damien, > Single LUN multi-actuator hard-disks are cappable to seek and execute > multiple commands in parallel. This capability is exposed to the host > using the Concurrent Positioning Ranges VPD page (SCSI) and Log (ATA). > Each positioning range describes the contiguous set of LBAs that an > actuator serves. I have to say that I prefer the multi-LUN model. > The first patch adds the block layer plumbing to expose concurrent > sector ranges of the device through sysfs as a sub-directory of the > device sysfs queue directory. So how do you envision this range reporting should work when putting DM/MD on top of a multi-actuator disk? And even without multi-actuator drives, how would you express concurrent ranges on a DM/MD device sitting on top of a several single-actuator devices? While I appreciate that it is easy to just export what the hardware reports in sysfs, I also think we should consider how filesystems would use that information. And how things would work outside of the simple fs-on-top-of-multi-actuator-drive case.
On 2021/08/06 12:42, Martin K. Petersen wrote: > > Damien, > >> Single LUN multi-actuator hard-disks are cappable to seek and execute >> multiple commands in parallel. This capability is exposed to the host >> using the Concurrent Positioning Ranges VPD page (SCSI) and Log (ATA). >> Each positioning range describes the contiguous set of LBAs that an >> actuator serves. > > I have to say that I prefer the multi-LUN model. It is certainly easier: nothing to do :) SATA, as usual, makes things harder... > >> The first patch adds the block layer plumbing to expose concurrent >> sector ranges of the device through sysfs as a sub-directory of the >> device sysfs queue directory. > > So how do you envision this range reporting should work when putting > DM/MD on top of a multi-actuator disk? The ranges are attached to the device request queue. So the DM/MD target driver can use that information from the underlying devices for whatever possible optimization. For the logical device exposed by the target driver, the ranges are not limits so they are not inherited. As is, right now, DM target devices will not show any range information for the logical devices they create, even if the underlying devices have multiple ranges. The DM/MD target driver is free to set any range information pertinent to the target. E.g. dm-liear could set the range information corresponding to sector chunks from different devices used to build the dm-linear device. > And even without multi-actuator drives, how would you express concurrent > ranges on a DM/MD device sitting on top of a several single-actuator > devices? Similar comment as above: it is up to the DM/MD target driver to decide if range information can be useful. For dm-linear, there are obvious cases where it is. Ex: 2 single actuator drives concatenated together can generate 2 ranges similarly to a real split-actuator disk. Expressing the chunks of a dm-linear setup as ranges may not always be possible though, that is, if we keep the assumption that a range is independent from others in terms of command execution. Ex: a dm-linear setup that shuffles a drive LBA mapping (high to low and low to high) has no business showing sector ranges. > While I appreciate that it is easy to just export what the hardware > reports in sysfs, I also think we should consider how filesystems would > use that information. And how things would work outside of the simple > fs-on-top-of-multi-actuator-drive case. Without any change anywhere in existing code (kernel and applications using raw disk accesses), things will just work as is. The multi/split actuator drive will behave as a single actuator drive, even for commands spanning range boundaries. Your guess on potential IOPS gains is as good as mine in this case. Performance will totally depend on the workload but will not be worse than an equivalent single actuator disk. FS block allocators can definitely use the range information to distribute writes among actuators. For reads, well, gains will depend on the workload, obviously, but optimizations at the block IO scheduler level can improve things too, especially if the drive is being used at a QD beyond its capability (that is, requests are accumulated in the IO scheduler). Similar write optimization can be achieved by applications using block device files directly. This series is intended for this case for now. FS and bloc IO scheduler optimization can be added later.
On 8/6/21 6:05 AM, Damien Le Moal wrote: > On 2021/08/06 12:42, Martin K. Petersen wrote: >> >> Damien, >> >>> Single LUN multi-actuator hard-disks are cappable to seek and execute >>> multiple commands in parallel. This capability is exposed to the host >>> using the Concurrent Positioning Ranges VPD page (SCSI) and Log (ATA). >>> Each positioning range describes the contiguous set of LBAs that an >>> actuator serves. >> >> I have to say that I prefer the multi-LUN model. > > It is certainly easier: nothing to do :) > SATA, as usual, makes things harder... > >> >>> The first patch adds the block layer plumbing to expose concurrent >>> sector ranges of the device through sysfs as a sub-directory of the >>> device sysfs queue directory. >> >> So how do you envision this range reporting should work when putting >> DM/MD on top of a multi-actuator disk? > > The ranges are attached to the device request queue. So the DM/MD target driver > can use that information from the underlying devices for whatever possible > optimization. For the logical device exposed by the target driver, the ranges > are not limits so they are not inherited. As is, right now, DM target devices > will not show any range information for the logical devices they create, even if > the underlying devices have multiple ranges. > > The DM/MD target driver is free to set any range information pertinent to the > target. E.g. dm-liear could set the range information corresponding to sector > chunks from different devices used to build the dm-linear device. > And indeed, that would be the easiest consumer. One 'just' needs to have a simple script converting the sysfs ranges into the corresponding dm-linear table definitions, and create one DM device for each range. That would simulate the multi-LUN approach. Not sure if that would warrant a 'real' DM target, seeing that it's fully scriptable. >> And even without multi-actuator drives, how would you express concurrent >> ranges on a DM/MD device sitting on top of a several single-actuator >> devices? > > Similar comment as above: it is up to the DM/MD target driver to decide if range > information can be useful. For dm-linear, there are obvious cases where it is. > Ex: 2 single actuator drives concatenated together can generate 2 ranges > similarly to a real split-actuator disk. Expressing the chunks of a dm-linear > setup as ranges may not always be possible though, that is, if we keep the > assumption that a range is independent from others in terms of command > execution. Ex: a dm-linear setup that shuffles a drive LBA mapping (high to low > and low to high) has no business showing sector ranges. > >> While I appreciate that it is easy to just export what the hardware >> reports in sysfs, I also think we should consider how filesystems would >> use that information. And how things would work outside of the simple >> fs-on-top-of-multi-actuator-drive case. > > Without any change anywhere in existing code (kernel and applications using raw > disk accesses), things will just work as is. The multi/split actuator drive will > behave as a single actuator drive, even for commands spanning range boundaries. > Your guess on potential IOPS gains is as good as mine in this case. Performance > will totally depend on the workload but will not be worse than an equivalent > single actuator disk. > > FS block allocators can definitely use the range information to distribute > writes among actuators. For reads, well, gains will depend on the workload, > obviously, but optimizations at the block IO scheduler level can improve things > too, especially if the drive is being used at a QD beyond its capability (that > is, requests are accumulated in the IO scheduler). > > Similar write optimization can be achieved by applications using block device > files directly. This series is intended for this case for now. FS and bloc IO > scheduler optimization can be added later. > > Rumours have it that Paolo Valente is working on adapting BFQ to utilize the range information for better actuator utilisation. And eventually one should modify filesystem utilities like xfs to adapt the metadata layout to multi-actuator drives. The _real_ fun starts once the HDD manufactures starts putting out multi-actuator SMR drives :-) Cheers, Hannes
On 2021/08/06 17:36, Hannes Reinecke wrote: > On 8/6/21 6:05 AM, Damien Le Moal wrote: >> On 2021/08/06 12:42, Martin K. Petersen wrote: >>> >>> Damien, >>> >>>> Single LUN multi-actuator hard-disks are cappable to seek and execute >>>> multiple commands in parallel. This capability is exposed to the host >>>> using the Concurrent Positioning Ranges VPD page (SCSI) and Log (ATA). >>>> Each positioning range describes the contiguous set of LBAs that an >>>> actuator serves. >>> >>> I have to say that I prefer the multi-LUN model. >> >> It is certainly easier: nothing to do :) >> SATA, as usual, makes things harder... >> >>> >>>> The first patch adds the block layer plumbing to expose concurrent >>>> sector ranges of the device through sysfs as a sub-directory of the >>>> device sysfs queue directory. >>> >>> So how do you envision this range reporting should work when putting >>> DM/MD on top of a multi-actuator disk? >> >> The ranges are attached to the device request queue. So the DM/MD target driver >> can use that information from the underlying devices for whatever possible >> optimization. For the logical device exposed by the target driver, the ranges >> are not limits so they are not inherited. As is, right now, DM target devices >> will not show any range information for the logical devices they create, even if >> the underlying devices have multiple ranges. >> >> The DM/MD target driver is free to set any range information pertinent to the >> target. E.g. dm-liear could set the range information corresponding to sector >> chunks from different devices used to build the dm-linear device. >> > And indeed, that would be the easiest consumer. > One 'just' needs to have a simple script converting the sysfs ranges > into the corresponding dm-linear table definitions, and create one DM > device for each range. > That would simulate the multi-LUN approach. > Not sure if that would warrant a 'real' DM target, seeing that it's > fully scriptable. > >>> And even without multi-actuator drives, how would you express concurrent >>> ranges on a DM/MD device sitting on top of a several single-actuator >>> devices? >> >> Similar comment as above: it is up to the DM/MD target driver to decide if range >> information can be useful. For dm-linear, there are obvious cases where it is. >> Ex: 2 single actuator drives concatenated together can generate 2 ranges >> similarly to a real split-actuator disk. Expressing the chunks of a dm-linear >> setup as ranges may not always be possible though, that is, if we keep the >> assumption that a range is independent from others in terms of command >> execution. Ex: a dm-linear setup that shuffles a drive LBA mapping (high to low >> and low to high) has no business showing sector ranges. >> >>> While I appreciate that it is easy to just export what the hardware >>> reports in sysfs, I also think we should consider how filesystems would >>> use that information. And how things would work outside of the simple >>> fs-on-top-of-multi-actuator-drive case. >> >> Without any change anywhere in existing code (kernel and applications using raw >> disk accesses), things will just work as is. The multi/split actuator drive will >> behave as a single actuator drive, even for commands spanning range boundaries. >> Your guess on potential IOPS gains is as good as mine in this case. Performance >> will totally depend on the workload but will not be worse than an equivalent >> single actuator disk. >> >> FS block allocators can definitely use the range information to distribute >> writes among actuators. For reads, well, gains will depend on the workload, >> obviously, but optimizations at the block IO scheduler level can improve things >> too, especially if the drive is being used at a QD beyond its capability (that >> is, requests are accumulated in the IO scheduler). >> >> Similar write optimization can be achieved by applications using block device >> files directly. This series is intended for this case for now. FS and bloc IO >> scheduler optimization can be added later. >> >> > Rumours have it that Paolo Valente is working on adapting BFQ to utilize > the range information for better actuator utilisation. Paolo has a talk on this subject scheduled for SNIA SDC 2021. https://storagedeveloper.org/events/sdc-2021/abstracts#hd-Walker > And eventually one should modify filesystem utilities like xfs to adapt > the metadata layout to multi-actuator drives. > > The _real_ fun starts once the HDD manufactures starts putting out > multi-actuator SMR drives :-) Well, that does not change things that much in the end. The same constraints remain, and the sector ranges will be aligned to zones. So no added difficulty. > > Cheers, > > Hannes >