* please revert the UFS HPB support @ 2021-10-21 14:42 Christoph Hellwig 2021-10-21 15:13 ` Jens Axboe 2021-10-23 1:54 ` Martin K. Petersen 0 siblings, 2 replies; 11+ messages in thread From: Christoph Hellwig @ 2021-10-21 14:42 UTC (permalink / raw) To: martin.petersen; +Cc: Jens Axboe, linux-scsi, linux-block Hi Martin, I just noticed the UFS HPB support landed in 5.15, and just as before it is completely broken by allocating another request on the same device and then reinserting it in the queue. It is bad enough that we have to live with blk_insert_cloned_request for dm-mpath, but this is too big of an API abuse to make it into a release. We need to drop this code ASAP, and I can prepare a patch for that. ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: please revert the UFS HPB support 2021-10-21 14:42 please revert the UFS HPB support Christoph Hellwig @ 2021-10-21 15:13 ` Jens Axboe 2021-10-21 15:15 ` Christoph Hellwig 2021-10-23 1:54 ` Martin K. Petersen 1 sibling, 1 reply; 11+ messages in thread From: Jens Axboe @ 2021-10-21 15:13 UTC (permalink / raw) To: Christoph Hellwig, martin.petersen; +Cc: linux-scsi, linux-block On 10/21/21 8:42 AM, Christoph Hellwig wrote: > Hi Martin, > > I just noticed the UFS HPB support landed in 5.15, and just as > before it is completely broken by allocating another request on > the same device and then reinserting it in the queue. It is bad > enough that we have to live with blk_insert_cloned_request for > dm-mpath, but this is too big of an API abuse to make it into > a release. We need to drop this code ASAP, and I can prepare > a patch for that. That sounds awful, do you have a link to the offending commit(s)? -- Jens Axboe ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: please revert the UFS HPB support 2021-10-21 15:13 ` Jens Axboe @ 2021-10-21 15:15 ` Christoph Hellwig 2021-10-21 15:17 ` Christoph Hellwig 0 siblings, 1 reply; 11+ messages in thread From: Christoph Hellwig @ 2021-10-21 15:15 UTC (permalink / raw) To: Jens Axboe; +Cc: Christoph Hellwig, martin.petersen, linux-scsi, linux-block On Thu, Oct 21, 2021 at 09:13:30AM -0600, Jens Axboe wrote: > On 10/21/21 8:42 AM, Christoph Hellwig wrote: > > Hi Martin, > > > > I just noticed the UFS HPB support landed in 5.15, and just as > > before it is completely broken by allocating another request on > > the same device and then reinserting it in the queue. It is bad > > enough that we have to live with blk_insert_cloned_request for > > dm-mpath, but this is too big of an API abuse to make it into > > a release. We need to drop this code ASAP, and I can prepare > > a patch for that. > > That sounds awful, do you have a link to the offending commit(s)? I'll need to look for it, busy in calls right now, but just grep for blk_insert_cloned_request. ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: please revert the UFS HPB support 2021-10-21 15:15 ` Christoph Hellwig @ 2021-10-21 15:17 ` Christoph Hellwig 2021-10-21 16:22 ` Bart Van Assche 0 siblings, 1 reply; 11+ messages in thread From: Christoph Hellwig @ 2021-10-21 15:17 UTC (permalink / raw) To: Jens Axboe; +Cc: Christoph Hellwig, martin.petersen, linux-scsi, linux-block On Thu, Oct 21, 2021 at 05:15:20PM +0200, Christoph Hellwig wrote: > > > I just noticed the UFS HPB support landed in 5.15, and just as > > > before it is completely broken by allocating another request on > > > the same device and then reinserting it in the queue. It is bad > > > enough that we have to live with blk_insert_cloned_request for > > > dm-mpath, but this is too big of an API abuse to make it into > > > a release. We need to drop this code ASAP, and I can prepare > > > a patch for that. > > > > That sounds awful, do you have a link to the offending commit(s)? > > I'll need to look for it, busy in calls right now, but just grep for > blk_insert_cloned_request. Might as well finish the git blame: commit 41d8a9333cc96f5ad4dd7a52786585338257d9f1 Author: Daejun Park <daejun7.park@samsung.com> Date: Mon Jul 12 18:00:25 2021 +0900 scsi: ufs: ufshpb: Add HPB 2.0 support Version 2.0 of HBP supports reads of varying sizes from 4KB to 1MB. A read operation <= 32KB is supported as single HPB read. A read between 36KB and 1MB is supported by a combination of write buffer command and HPB read command to deliver more PPN. The write buffer commands may not be issued immediately due to busy tags. To use HPB read more aggressively, the driver can requeue the write buffer command. The requeue threshold is implemented as timeout and can be modified with requeue_timeout_ms entry in sysfs. ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: please revert the UFS HPB support 2021-10-21 15:17 ` Christoph Hellwig @ 2021-10-21 16:22 ` Bart Van Assche 2021-10-23 15:43 ` James Bottomley [not found] ` <CGME20211023154316epcas2p208f95cf1e4a87a4b61d2daf1a2b3c725@epcms2p3> 0 siblings, 2 replies; 11+ messages in thread From: Bart Van Assche @ 2021-10-21 16:22 UTC (permalink / raw) To: Christoph Hellwig, Jens Axboe Cc: martin.petersen, linux-scsi, linux-block, Daejun Park, Jaegeuk Kim On 10/21/21 8:17 AM, Christoph Hellwig wrote: > On Thu, Oct 21, 2021 at 05:15:20PM +0200, Christoph Hellwig wrote: >>>> I just noticed the UFS HPB support landed in 5.15, and just as >>>> before it is completely broken by allocating another request on >>>> the same device and then reinserting it in the queue. It is bad >>>> enough that we have to live with blk_insert_cloned_request for >>>> dm-mpath, but this is too big of an API abuse to make it into >>>> a release. We need to drop this code ASAP, and I can prepare >>>> a patch for that. >>> >>> That sounds awful, do you have a link to the offending commit(s)? >> >> I'll need to look for it, busy in calls right now, but just grep for >> blk_insert_cloned_request. > > Might as well finish the git blame: > > commit 41d8a9333cc96f5ad4dd7a52786585338257d9f1 > Author: Daejun Park <daejun7.park@samsung.com> > Date: Mon Jul 12 18:00:25 2021 +0900 > > scsi: ufs: ufshpb: Add HPB 2.0 support > > Version 2.0 of HBP supports reads of varying sizes from 4KB to 1MB. > > A read operation <= 32KB is supported as single HPB read. A read between > 36KB and 1MB is supported by a combination of write buffer command and HPB > read command to deliver more PPN. The write buffer commands may not be > issued immediately due to busy tags. To use HPB read more aggressively, the > driver can requeue the write buffer command. The requeue threshold is > implemented as timeout and can be modified with requeue_timeout_ms entry in > sysfs. (+Daejun) Daejun, can the HPB code be reworked such that it does not use blk_insert_cloned_request()? I'm concerned that if the HPB code is not reworked that it will be removed from the upstream kernel. Thanks, Bart. ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: please revert the UFS HPB support 2021-10-21 16:22 ` Bart Van Assche @ 2021-10-23 15:43 ` James Bottomley [not found] ` <CGME20211023154316epcas2p208f95cf1e4a87a4b61d2daf1a2b3c725@epcms2p3> 1 sibling, 0 replies; 11+ messages in thread From: James Bottomley @ 2021-10-23 15:43 UTC (permalink / raw) To: Bart Van Assche, Christoph Hellwig, Jens Axboe Cc: martin.petersen, linux-scsi, linux-block, Daejun Park, Jaegeuk Kim On Thu, 2021-10-21 at 09:22 -0700, Bart Van Assche wrote: > On 10/21/21 8:17 AM, Christoph Hellwig wrote: > > On Thu, Oct 21, 2021 at 05:15:20PM +0200, Christoph Hellwig wrote: > > > > > I just noticed the UFS HPB support landed in 5.15, and just > > > > > as before it is completely broken by allocating another > > > > > request on the same device and then reinserting it in the > > > > > queue. It is bad enough that we have to live with > > > > > blk_insert_cloned_request for dm-mpath, but this is too big > > > > > of an API abuse to make it into a release. We need to drop > > > > > this code ASAP, and I can prepare a patch for that. > > > > > > > > That sounds awful, do you have a link to the offending > > > > commit(s)? > > > > > > I'll need to look for it, busy in calls right now, but just grep > > > for blk_insert_cloned_request. > > > > Might as well finish the git blame: > > > > commit 41d8a9333cc96f5ad4dd7a52786585338257d9f1 > > Author: Daejun Park <daejun7.park@samsung.com> > > Date: Mon Jul 12 18:00:25 2021 +0900 > > > > scsi: ufs: ufshpb: Add HPB 2.0 support > > > > Version 2.0 of HBP supports reads of varying sizes from 4KB to > > 1MB. > > > > A read operation <= 32KB is supported as single HPB read. A > > read between > > 36KB and 1MB is supported by a combination of write buffer > > command and HPB > > read command to deliver more PPN. The write buffer commands > > may not be > > issued immediately due to busy tags. To use HPB read more > > aggressively, the > > driver can requeue the write buffer command. The requeue > > threshold is > > implemented as timeout and can be modified with > > requeue_timeout_ms entry in > > sysfs. > > (+Daejun) > > Daejun, can the HPB code be reworked such that it does not use > blk_insert_cloned_request()? I'm concerned that if the HPB code is > not reworked that it will be removed from the upstream kernel. Just to give urgency to Bart's request: we have two or three weeks before the kernel is due to go final. Can the problems identified by Christoph be fixed within that timeframe? Specifically, looking at the paper you reference, it only uses READ BUFFER for the host cache sharing. Since the JDEC standard appears to be proprietary, I have no method of understanding why the driver now uses WRITE BUFFER as well, but it appears to be a simple optimization. If you can cut out the WRITE BUFFER code, blk_insert_cloned_request() will also be gone and thus the API abuse. Can you get us a simple patch doing this ASAP so we don't have to revert the driver? James ^ permalink raw reply [flat|nested] 11+ messages in thread
[parent not found: <CGME20211023154316epcas2p208f95cf1e4a87a4b61d2daf1a2b3c725@epcms2p3>]
* RE: please revert the UFS HPB support [not found] ` <CGME20211023154316epcas2p208f95cf1e4a87a4b61d2daf1a2b3c725@epcms2p3> @ 2021-10-25 5:16 ` Daejun Park 2021-10-25 7:07 ` Christoph Hellwig 2021-10-25 11:39 ` James Bottomley 0 siblings, 2 replies; 11+ messages in thread From: Daejun Park @ 2021-10-25 5:16 UTC (permalink / raw) To: James Bottomley, Bart Van Assche, Christoph Hellwig, Jens Axboe Cc: martin.petersen, linux-scsi, linux-block, Daejun Park, Jaegeuk Kim > On Thu, 2021-10-21 at 09:22 -0700, Bart Van Assche wrote: > > On 10/21/21 8:17 AM, Christoph Hellwig wrote: > > > On Thu, Oct 21, 2021 at 05:15:20PM +0200, Christoph Hellwig wrote: > > > > > > I just noticed the UFS HPB support landed in 5.15, and just > > > > > > as before it is completely broken by allocating another > > > > > > request on the same device and then reinserting it in the > > > > > > queue. It is bad enough that we have to live with > > > > > > blk_insert_cloned_request for dm-mpath, but this is too big > > > > > > of an API abuse to make it into a release. We need to drop > > > > > > this code ASAP, and I can prepare a patch for that. > > > > > > > > > > That sounds awful, do you have a link to the offending > > > > > commit(s)? > > > > > > > > I'll need to look for it, busy in calls right now, but just grep > > > > for blk_insert_cloned_request. > > > > > > Might as well finish the git blame: > > > > > > commit 41d8a9333cc96f5ad4dd7a52786585338257d9f1 > > > Author: Daejun Park <daejun7.park@samsung.com> > > > Date: Mon Jul 12 18:00:25 2021 +0900 > > > > > > scsi: ufs: ufshpb: Add HPB 2.0 support > > > > > > Version 2.0 of HBP supports reads of varying sizes from 4KB to > > > 1MB. > > > > > > A read operation <= 32KB is supported as single HPB read. A > > > read between > > > 36KB and 1MB is supported by a combination of write buffer > > > command and HPB > > > read command to deliver more PPN. The write buffer commands > > > may not be > > > issued immediately due to busy tags. To use HPB read more > > > aggressively, the > > > driver can requeue the write buffer command. The requeue > > > threshold is > > > implemented as timeout and can be modified with > > > requeue_timeout_ms entry in > > > sysfs. > > > > (+Daejun) > > > > Daejun, can the HPB code be reworked such that it does not use > > blk_insert_cloned_request()? I'm concerned that if the HPB code is > > not reworked that it will be removed from the upstream kernel. > > Just to give urgency to Bart's request: we have two or three weeks > before the kernel is due to go final. Can the problems identified by > Christoph be fixed within that timeframe? I'm checking to see if I can replace blk_execute_rq_nowait with blk_insert_cloned_request in the HPB code. > > Specifically, looking at the paper you reference, it only uses READ > BUFFER for the host cache sharing. Since the JDEC standard appears to > be proprietary, I have no method of understanding why the driver now > uses WRITE BUFFER as well, but it appears to be a simple optimization. > If you can cut out the WRITE BUFFER code, blk_insert_cloned_request() > will also be gone and thus the API abuse. Can you get us a simple > patch doing this ASAP so we don't have to revert the driver? If WRITE BUFFER is not used, only READs with a size of 32KB or less can be changed to HPB READs. This becomes a limiting factor in how READ performance can be improved by the HPB. Thanks, Daejun ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: please revert the UFS HPB support 2021-10-25 5:16 ` Daejun Park @ 2021-10-25 7:07 ` Christoph Hellwig 2021-10-25 11:39 ` James Bottomley 1 sibling, 0 replies; 11+ messages in thread From: Christoph Hellwig @ 2021-10-25 7:07 UTC (permalink / raw) To: Daejun Park Cc: James Bottomley, Bart Van Assche, Christoph Hellwig, Jens Axboe, martin.petersen, linux-scsi, linux-block, Jaegeuk Kim On Mon, Oct 25, 2021 at 02:16:54PM +0900, Daejun Park wrote: > > before the kernel is due to go final. Can the problems identified by > > Christoph be fixed within that timeframe? > > I'm checking to see if I can replace blk_execute_rq_nowait with > blk_insert_cloned_request in the HPB code. blk_insert_cloned_request is part of the problem. You can't just fan out one request into two on the same queue. FYI, 5.15 is supposed to be released end of this week (unless an -rc8) happens. I don't think we can sit this out, we need to revert (or at least disable) the code now. ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: please revert the UFS HPB support 2021-10-25 5:16 ` Daejun Park 2021-10-25 7:07 ` Christoph Hellwig @ 2021-10-25 11:39 ` James Bottomley 1 sibling, 0 replies; 11+ messages in thread From: James Bottomley @ 2021-10-25 11:39 UTC (permalink / raw) To: daejun7.park, Bart Van Assche, Christoph Hellwig, Jens Axboe Cc: martin.petersen, linux-scsi, linux-block, Jaegeuk Kim On Mon, 2021-10-25 at 14:16 +0900, Daejun Park wrote: > > On Thu, 2021-10-21 at 09:22 -0700, Bart Van Assche wrote: > > > On 10/21/21 8:17 AM, Christoph Hellwig wrote: > > > > On Thu, Oct 21, 2021 at 05:15:20PM +0200, Christoph Hellwig > > > > wrote: > > > > > > > I just noticed the UFS HPB support landed in 5.15, and > > > > > > > just as before it is completely broken by allocating > > > > > > > another request on the same device and then reinserting > > > > > > > it in the queue. It is bad enough that we have to live > > > > > > > with blk_insert_cloned_request for dm-mpath, but this is > > > > > > > too big of an API abuse to make it into a release. We > > > > > > > need to drop this code ASAP, and I can prepare a patch > > > > > > > for that. > > > > > > > > > > > > That sounds awful, do you have a link to the offending > > > > > > commit(s)? > > > > > > > > > > I'll need to look for it, busy in calls right now, but just > > > > > grep for blk_insert_cloned_request. > > > > > > > > Might as well finish the git blame: > > > > > > > > commit 41d8a9333cc96f5ad4dd7a52786585338257d9f1 > > > > Author: Daejun Park <daejun7.park@samsung.com> > > > > Date: Mon Jul 12 18:00:25 2021 +0900 > > > > > > > > scsi: ufs: ufshpb: Add HPB 2.0 support > > > > > > > > Version 2.0 of HBP supports reads of varying sizes from > > > > 4KB to 1MB. > > > > > > > > A read operation <= 32KB is supported as single HPB read. > > > > A read between > > > > 36KB and 1MB is supported by a combination of write buffer > > > > command and HPB > > > > read command to deliver more PPN. The write buffer > > > > commands may not be > > > > issued immediately due to busy tags. To use HPB read more > > > > aggressively, the > > > > driver can requeue the write buffer command. The requeue > > > > threshold is > > > > implemented as timeout and can be modified with > > > > requeue_timeout_ms entry in > > > > sysfs. > > > > > > (+Daejun) > > > > > > Daejun, can the HPB code be reworked such that it does not use > > > blk_insert_cloned_request()? I'm concerned that if the HPB code > > > is not reworked that it will be removed from the upstream kernel. > > > > Just to give urgency to Bart's request: we have two or three weeks > > before the kernel is due to go final. Can the problems identified > > by Christoph be fixed within that timeframe? > > I'm checking to see if I can replace blk_execute_rq_nowait with > blk_insert_cloned_request in the HPB code. That's not going to help: removing blk_insert_cloned_request() is what we need. > > Specifically, looking at the paper you reference, it only uses READ > > BUFFER for the host cache sharing. Since the JDEC standard appears > > to be proprietary, I have no method of understanding why the driver > > now uses WRITE BUFFER as well, but it appears to be a simple > > optimization. If you can cut out the WRITE BUFFER code, > > blk_insert_cloned_request() will also be gone and thus the API > > abuse. Can you get us a simple patch doing this ASAP so we don't > > have to revert the driver? > > If WRITE BUFFER is not used, only READs with a size of 32KB or less > can be changed to HPB READs. This becomes a limiting factor in how > READ performance can be improved by the HPB. Well, precisely: it's an optimization. It can be removed now and you can work out how to add the code back without the problem API later. We're running critically short of time to fix this, so unless you have a different proposal, it's either this hunk of code or the entire driver. James ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: please revert the UFS HPB support 2021-10-21 14:42 please revert the UFS HPB support Christoph Hellwig 2021-10-21 15:13 ` Jens Axboe @ 2021-10-23 1:54 ` Martin K. Petersen 2021-10-23 4:40 ` Christoph Hellwig 1 sibling, 1 reply; 11+ messages in thread From: Martin K. Petersen @ 2021-10-23 1:54 UTC (permalink / raw) To: Christoph Hellwig Cc: martin.petersen, Jens Axboe, linux-scsi, linux-block, Greg KH Hi Christoph, > I just noticed the UFS HPB support landed in 5.15, and just as before > it is completely broken by allocating another request on the same > device and then reinserting it in the queue. It is bad enough that we > have to live with blk_insert_cloned_request for dm-mpath, but this is > too big of an API abuse to make it into a release. We need to drop > this code ASAP, and I can prepare a patch for that. The series went through 40 iterations on the list prior to being merged. I don't recall a better approach to reconcile the HPB model with the stack being offered during that process? As much as I don't like HPB, all the major UFS subsystem stakeholders are behind it. The hardware is shipping and various device stacks already adopted support for it. At this stage I don't think dropping the code is a way forward. I am much more in favor of having a productive discussion about how to go about addressing the problems with the queuing model... -- Martin K. Petersen Oracle Linux Engineering ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: please revert the UFS HPB support 2021-10-23 1:54 ` Martin K. Petersen @ 2021-10-23 4:40 ` Christoph Hellwig 0 siblings, 0 replies; 11+ messages in thread From: Christoph Hellwig @ 2021-10-23 4:40 UTC (permalink / raw) To: Martin K. Petersen Cc: Christoph Hellwig, Jens Axboe, linux-scsi, linux-block, Greg KH On Fri, Oct 22, 2021 at 09:54:44PM -0400, Martin K. Petersen wrote: > The series went through 40 iterations on the list prior to being merged. > I don't recall a better approach to reconcile the HPB model with the > stack being offered during that process? > > As much as I don't like HPB, all the major UFS subsystem stakeholders > are behind it. The hardware is shipping and various device stacks > already adopted support for it. At this stage I don't think dropping the > code is a way forward. I am much more in favor of having a productive > discussion about how to go about addressing the problems with the > queuing model... This is іs not about HPB about a feature beeing a bad idea. I explained that at least a dozend times, and there's been no sensible counter arguments to that but it has been merged anyway. (FYI Zoned devices are the obvious and old answer). But this implementation is simply completely broken from the block layer POV and we must not release a kernel with that brokenness in it. ^ permalink raw reply [flat|nested] 11+ messages in thread
end of thread, other threads:[~2021-10-25 11:39 UTC | newest]
Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
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2021-10-21 14:42 please revert the UFS HPB support Christoph Hellwig
2021-10-21 15:13 ` Jens Axboe
2021-10-21 15:15 ` Christoph Hellwig
2021-10-21 15:17 ` Christoph Hellwig
2021-10-21 16:22 ` Bart Van Assche
2021-10-23 15:43 ` James Bottomley
[not found] ` <CGME20211023154316epcas2p208f95cf1e4a87a4b61d2daf1a2b3c725@epcms2p3>
2021-10-25 5:16 ` Daejun Park
2021-10-25 7:07 ` Christoph Hellwig
2021-10-25 11:39 ` James Bottomley
2021-10-23 1:54 ` Martin K. Petersen
2021-10-23 4:40 ` Christoph Hellwig
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