Re: [stable-4.14 00/23] block/scsi multiqueue performance enhancement and

Re: [stable-4.14 00/23] block/scsi multiqueue performance enhancement and

[Jack Wang]

Hi Greg,

Thanks for quick reply. Please see reply inline.



Greg KH <gregkh@linuxfoundation.org> 于2018年7月23日周一 下午3:34写道：
>
> On Mon, Jul 23, 2018 at 03:24:22PM +0200, Jack Wang wrote:
> > Hi Greg,
> >
> > Please consider this patchset, which include block/scsi multiqueue performance
> > enhancement and bugfix.
>
> What exactly is the performance enhancement?  How can you measure it?
> How did you measure it?
I'm testing on SRP/IBNBD using fio, I've seen +10% with mix IO load,
and 50% improvement on small IO (bs=512.) with the patchset.

>
> Which one(s) are the bugfixes in this series?  Why not just submit those
> separately as they should be "obvious fixes", right?
We had queue stall problem on shared hctx restart, my colleague Roman
reported to upstream:
https://lkml.org/lkml/2017/10/18/263
the patch wasn't taken by upstream, and a bigger patchset from Lei
Ming was accepted instread with revert and further bugfix later on.

following patches meant for improving performance on scsi-mq, and also
contains the attempt to fix the queue stall problem
 358a3a6bccb7 ("blk-mq: don't handle TAG_SHARED in restart")
  blk-mq-sched: move actual dispatching into one helper
  blk-mq: introduce .get_budget and .put_budget in blk_mq_ops
  sbitmap: introduce __sbitmap_for_each_set()
  blk-mq-sched: improve dispatching from sw queue
  scsi: allow passing in null rq to scsi_prep_state_check()
  scsi: implement .get_budget and .put_budget for blk-mq
  SCSI: don't get target/host busy_count in scsi_mq_get_budget()
  blk-mq: don't handle TAG_SHARED in restart
  blk-mq: don't restart queue when .get_budget returns BLK_STS_RESOURCE
  blk-mq: don't handle failure in .get_budget

Following is independent fix:
blk-mq: quiesce queue during switching io sched and updating nr_requests
blk-mq: fix issue with shared tag queue re-running

These are clearup for flush request handling:
  blk-flush: don't run queue for requests bypassing flush
  block: pass 'run_queue' to blk_mq_request_bypass_insert
  blk-flush: use blk_mq_request_bypass_insert()
  blk-mq-sched: decide how to handle flush rq via RQF_FLUSH_SEQ
  blk-mq: move blk_mq_put_driver_tag*() into blk-mq.h
  blk-mq: don't allocate driver tag upfront for flush rq

The left are following up fixes.
>
> And why didn't you cc: the subsystem maintainer and mailing list here?
> I need their ack before I could take these.
Sorry, my mistake, now add Jens, linux-block, ilnux-scsi in reply.

Sorry for confusion.
>
> thanks,
>
> greg k-h

Regards,
Jack Wang

Re: [stable-4.14 00/23] block/scsi multiqueue performance enhancement and

[Jens Axboe]

On 7/23/18 9:00 AM, Jack Wang wrote:
> Hi Greg,
> 
> Thanks for quick reply. Please see reply inline.
> 
> 
> 
> Greg KH <gregkh@linuxfoundation.org> 于2018年7月23日周一 下午3:34写道：
>>
>> On Mon, Jul 23, 2018 at 03:24:22PM +0200, Jack Wang wrote:
>>> Hi Greg,
>>>
>>> Please consider this patchset, which include block/scsi multiqueue performance
>>> enhancement and bugfix.
>>
>> What exactly is the performance enhancement?  How can you measure it?
>> How did you measure it?
> I'm testing on SRP/IBNBD using fio, I've seen +10% with mix IO load,
> and 50% improvement on small IO (bs=512.) with the patchset.

Big nak on backporting this huge series, it's a lot of core changes.
It's way beyond the scope of a stable fix backport.

-- 
Jens Axboe

Re: [stable-4.14 00/23] block/scsi multiqueue performance enhancement and

[Jack Wang]

Jens Axboe <axboe@kernel.dk> 于2018年7月23日周一 下午5:05写道：
>
> On 7/23/18 9:00 AM, Jack Wang wrote:
> > Hi Greg,
> >
> > Thanks for quick reply. Please see reply inline.
> >
> >
> >
> > Greg KH <gregkh@linuxfoundation.org> 于2018年7月23日周一 下午3:34写道：
> >>
> >> On Mon, Jul 23, 2018 at 03:24:22PM +0200, Jack Wang wrote:
> >>> Hi Greg,
> >>>
> >>> Please consider this patchset, which include block/scsi multiqueue performance
> >>> enhancement and bugfix.
> >>
> >> What exactly is the performance enhancement?  How can you measure it?
> >> How did you measure it?
> > I'm testing on SRP/IBNBD using fio, I've seen +10% with mix IO load,
> > and 50% improvement on small IO (bs=512.) with the patchset.
>
> Big nak on backporting this huge series, it's a lot of core changes.
> It's way beyond the scope of a stable fix backport.
>
> --
> Jens Axboe
>
OK, could you shed light on how could we fix the queue stall problem on 4.14?
My colleague Roman reported to upstream:
https://lkml.org/lkml/2017/10/18/263

It's still there on latest 4.14.

Thanks,
Jack

Re: [stable-4.14 00/23] block/scsi multiqueue performance enhancement and

[Jens Axboe]

On 7/23/18 9:28 AM, Jack Wang wrote:
> Jens Axboe <axboe@kernel.dk> 于2018年7月23日周一 下午5:05写道：
>>
>> On 7/23/18 9:00 AM, Jack Wang wrote:
>>> Hi Greg,
>>>
>>> Thanks for quick reply. Please see reply inline.
>>>
>>>
>>>
>>> Greg KH <gregkh@linuxfoundation.org> 于2018年7月23日周一 下午3:34写道：
>>>>
>>>> On Mon, Jul 23, 2018 at 03:24:22PM +0200, Jack Wang wrote:
>>>>> Hi Greg,
>>>>>
>>>>> Please consider this patchset, which include block/scsi multiqueue performance
>>>>> enhancement and bugfix.
>>>>
>>>> What exactly is the performance enhancement?  How can you measure it?
>>>> How did you measure it?
>>> I'm testing on SRP/IBNBD using fio, I've seen +10% with mix IO load,
>>> and 50% improvement on small IO (bs=512.) with the patchset.
>>
>> Big nak on backporting this huge series, it's a lot of core changes.
>> It's way beyond the scope of a stable fix backport.
>>
>> --
>> Jens Axboe
>>
> OK, could you shed light on how could we fix the queue stall problem on 4.14?
> My colleague Roman reported to upstream:
> https://lkml.org/lkml/2017/10/18/263
> 
> It's still there on latest 4.14.

The proposed patch is a helluva lot simpler than doing a 23 patch selective
backport.

-- 
Jens Axboe

Re: [stable-4.14 00/23] block/scsi multiqueue performance enhancement and

[Jack Wang]

Jens Axboe <axboe@kernel.dk> 于2018年7月23日周一 下午5:31写道：
>
> On 7/23/18 9:28 AM, Jack Wang wrote:
> > Jens Axboe <axboe@kernel.dk> 于2018年7月23日周一 下午5:05写道：
> >>
> >> On 7/23/18 9:00 AM, Jack Wang wrote:
> >>> Hi Greg,
> >>>
> >>> Thanks for quick reply. Please see reply inline.
> >>>
> >>>
> >>>
> >>> Greg KH <gregkh@linuxfoundation.org> 于2018年7月23日周一 下午3:34写道：
> >>>>
> >>>> On Mon, Jul 23, 2018 at 03:24:22PM +0200, Jack Wang wrote:
> >>>>> Hi Greg,
> >>>>>
> >>>>> Please consider this patchset, which include block/scsi multiqueue performance
> >>>>> enhancement and bugfix.
> >>>>
> >>>> What exactly is the performance enhancement?  How can you measure it?
> >>>> How did you measure it?
> >>> I'm testing on SRP/IBNBD using fio, I've seen +10% with mix IO load,
> >>> and 50% improvement on small IO (bs=512.) with the patchset.
> >>
> >> Big nak on backporting this huge series, it's a lot of core changes.
> >> It's way beyond the scope of a stable fix backport.
> >>
> >> --
> >> Jens Axboe
> >>
> > OK, could you shed light on how could we fix the queue stall problem on 4.14?
> > My colleague Roman reported to upstream:
> > https://lkml.org/lkml/2017/10/18/263
> >
> > It's still there on latest 4.14.
>
> The proposed patch is a helluva lot simpler than doing a 23 patch selective
> backport.
>
> --
> Jens Axboe
>
Do you think it make sense to port Roman's patch to upstream 4.14?

So others would also be benifitial?
On the other side, stable tree only takes patches accepted into Linus tree.

Thanks,
Jack