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RE: [PATCH] block: loose check on sg gap

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  RE: [PATCH] block: loose check on sg gap Dexuan Cui <decui@microsoft.com> - 2017-01-11 06:20 +0100
    Re: [PATCH] block: loose check on sg gap Ming Lei <ming.lei@canonical.com> - 2017-01-12 04:00 +0100
      RE: [PATCH] block: loose check on sg gap Dexuan Cui <decui@microsoft.com> - 2017-01-12 04:20 +0100

#1556209 — RE: [PATCH] block: loose check on sg gap

> From: Dexuan Cui
> Sent: Tuesday, December 20, 2016 11:41
> To: 'Jens Axboe' <axboe@fb.com>; Ming Lei <ming.lei@canonical.com>
> Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>; linux-block
> <linux-block@vger.kernel.org>; Christoph Hellwig <hch@infradead.org>;
> Vitaly Kuznetsov <vkuznets@redhat.com>; Keith Busch
> <keith.busch@intel.com>; Hannes Reinecke <hare@suse.de>; Mike Christie
> <mchristi@redhat.com>; Martin K. Petersen <martin.petersen@oracle.com>;
> Toshi Kani <toshi.kani@hpe.com>; Dan Williams <dan.j.williams@intel.com>;
> Damien Le Moal <damien.lemoal@hgst.com>
> Subject: RE: [PATCH] block: loose check on sg gap
> 
> > From: Jens Axboe [mailto:axboe@fb.com]
> > Sent: Tuesday, December 20, 2016 10:31
> > To: Ming Lei <ming.lei@canonical.com>
> > Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>; linux-block
> <linux-
> > block@vger.kernel.org>; Christoph Hellwig <hch@infradead.org>; Dexuan
> Cui
> > <decui@microsoft.com>; Vitaly Kuznetsov <vkuznets@redhat.com>; Keith
> Busch
> > <keith.busch@intel.com>; Hannes Reinecke <hare@suse.de>; Mike Christie
> > <mchristi@redhat.com>; Martin K. Petersen
> <martin.petersen@oracle.com>;
> > Toshi Kani <toshi.kani@hpe.com>; Dan Williams
> <dan.j.williams@intel.com>;
> > Damien Le Moal <damien.lemoal@hgst.com>
> > Subject: Re: [PATCH] block: loose check on sg gap
> >
> > On 12/19/2016 07:07 PM, Ming Lei wrote:
> > > On Sun, Dec 18, 2016 at 12:49 AM, Jens Axboe <axboe@fb.com> wrote:
> > >> On 12/17/2016 03:49 AM, Ming Lei wrote:
> > >>> If the last bvec of the 1st bio and the 1st bvec of the next
> > >>> bio are contineous physically, and the latter can be merged
> > >>> to last segment of the 1st bio, we should think they don't
> > >>> violate sg gap(or virt boundary) limit.
> > >>>
> > >>> Both Vitaly and Dexuan reported lots of unmergeable small bios
> > >>> are observed when running mkfs on Hyper-V virtual storage, and
> > >>> performance becomes quite low, so this patch is figured out for
> > >>> fixing the performance issue.
> > >>>
> > >>> The same issue should exist on NVMe too sine it sets virt boundary
> too.
> > >>
> > >> It looks pretty reasonable to me. I'll queue it up for some testing,
> > >> changes like this always make me a little nervous.
> > >
> > > Understood.
> > >
> > > But given it is still in early stage of 4.10 cycle, seems fine to expose
> > > it now, and we should have enough time to fix it if there might be
> > > regressions.
> > >
> > > BTW, it passes my xfstest(ext4) over sata/NVMe.
> >
> > It's been fine here in testing, too. I'm not worried about performance
> > regressions, those we can always fix. Merging makes me worried about
> > corruption, and those regressions are much worse.
> >
> > Any reason we need to rush this? I'd be more comfortable pushing this to
> > 4.11, unless there are strong reasons this should make 4.10.
> >
> > --
> > Jens Axboe
> 
> Hi Jens,
> 
> As far as I know, the patch is important to popular Linux distros,
> e.g. at least Ubuntu 14.04.5, 16.x and RHEL 7.3, when they run on
> Hyper-V/Azure, because they can suffer from a pretty bad
> throughput/latency
> in some cases, e.g. mkfs.ext4 for a 100GB partition can take 8 minutes, but
> with the patch, it only takes 1 second.
> 
> -- Dexuan

Hi Ming, Jens,
Did you find any issue later when testing with the patch?

May I know if it's possible to have it in 4.10 considering the above impact?

Is it on some temporary branch of linux-block.git? Looks not.

Thanks,
-- Dexuan

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#1557078

On Wed, Jan 11, 2017 at 1:10 PM, Dexuan Cui <decui@microsoft.com> wrote:
>> From: Dexuan Cui
>> Sent: Tuesday, December 20, 2016 11:41
>> To: 'Jens Axboe' <axboe@fb.com>; Ming Lei <ming.lei@canonical.com>
>> Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>; linux-block
>> <linux-block@vger.kernel.org>; Christoph Hellwig <hch@infradead.org>;
>> Vitaly Kuznetsov <vkuznets@redhat.com>; Keith Busch
>> <keith.busch@intel.com>; Hannes Reinecke <hare@suse.de>; Mike Christie
>> <mchristi@redhat.com>; Martin K. Petersen <martin.petersen@oracle.com>;
>> Toshi Kani <toshi.kani@hpe.com>; Dan Williams <dan.j.williams@intel.com>;
>> Damien Le Moal <damien.lemoal@hgst.com>
>> Subject: RE: [PATCH] block: loose check on sg gap
>>
>> > From: Jens Axboe [mailto:axboe@fb.com]
>> > Sent: Tuesday, December 20, 2016 10:31
>> > To: Ming Lei <ming.lei@canonical.com>
>> > Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>; linux-block
>> <linux-
>> > block@vger.kernel.org>; Christoph Hellwig <hch@infradead.org>; Dexuan
>> Cui
>> > <decui@microsoft.com>; Vitaly Kuznetsov <vkuznets@redhat.com>; Keith
>> Busch
>> > <keith.busch@intel.com>; Hannes Reinecke <hare@suse.de>; Mike Christie
>> > <mchristi@redhat.com>; Martin K. Petersen
>> <martin.petersen@oracle.com>;
>> > Toshi Kani <toshi.kani@hpe.com>; Dan Williams
>> <dan.j.williams@intel.com>;
>> > Damien Le Moal <damien.lemoal@hgst.com>
>> > Subject: Re: [PATCH] block: loose check on sg gap
>> >
>> > On 12/19/2016 07:07 PM, Ming Lei wrote:
>> > > On Sun, Dec 18, 2016 at 12:49 AM, Jens Axboe <axboe@fb.com> wrote:
>> > >> On 12/17/2016 03:49 AM, Ming Lei wrote:
>> > >>> If the last bvec of the 1st bio and the 1st bvec of the next
>> > >>> bio are contineous physically, and the latter can be merged
>> > >>> to last segment of the 1st bio, we should think they don't
>> > >>> violate sg gap(or virt boundary) limit.
>> > >>>
>> > >>> Both Vitaly and Dexuan reported lots of unmergeable small bios
>> > >>> are observed when running mkfs on Hyper-V virtual storage, and
>> > >>> performance becomes quite low, so this patch is figured out for
>> > >>> fixing the performance issue.
>> > >>>
>> > >>> The same issue should exist on NVMe too sine it sets virt boundary
>> too.
>> > >>
>> > >> It looks pretty reasonable to me. I'll queue it up for some testing,
>> > >> changes like this always make me a little nervous.
>> > >
>> > > Understood.
>> > >
>> > > But given it is still in early stage of 4.10 cycle, seems fine to expose
>> > > it now, and we should have enough time to fix it if there might be
>> > > regressions.
>> > >
>> > > BTW, it passes my xfstest(ext4) over sata/NVMe.
>> >
>> > It's been fine here in testing, too. I'm not worried about performance
>> > regressions, those we can always fix. Merging makes me worried about
>> > corruption, and those regressions are much worse.
>> >
>> > Any reason we need to rush this? I'd be more comfortable pushing this to
>> > 4.11, unless there are strong reasons this should make 4.10.
>> >
>> > --
>> > Jens Axboe
>>
>> Hi Jens,
>>
>> As far as I know, the patch is important to popular Linux distros,
>> e.g. at least Ubuntu 14.04.5, 16.x and RHEL 7.3, when they run on
>> Hyper-V/Azure, because they can suffer from a pretty bad
>> throughput/latency
>> in some cases, e.g. mkfs.ext4 for a 100GB partition can take 8 minutes, but
>> with the patch, it only takes 1 second.
>>
>> -- Dexuan
>
> Hi Ming, Jens,
> Did you find any issue later when testing with the patch?
>
> May I know if it's possible to have it in 4.10 considering the above impact?
>
> Is it on some temporary branch of linux-block.git? Looks not.

Dexuan, Jens has said that this patch may land v4.11, so just wait a release
and let it expose into more tests.

Thanks,
Ming

[toc] | [prev] | [next] | [standalone]

#1557082

> From: Ming Lei [mailto:ming.lei@canonical.com]
> Sent: Thursday, January 12, 2017 10:54
> To: Dexuan Cui <decui@microsoft.com>
> Cc: Jens Axboe <axboe@fb.com>; Linux Kernel Mailing List <linux-
> kernel@vger.kernel.org>; linux-block <linux-block@vger.kernel.org>;
> Christoph Hellwig <hch@infradead.org>; Vitaly Kuznetsov
> <vkuznets@redhat.com>; Keith Busch <keith.busch@intel.com>; Hannes
> Reinecke <hare@suse.de>; Mike Christie <mchristi@redhat.com>; Martin K.
> Petersen <martin.petersen@oracle.com>; Toshi Kani <toshi.kani@hpe.com>;
> Dan Williams <dan.j.williams@intel.com>; Damien Le Moal
> <damien.lemoal@hgst.com>; KY Srinivasan <kys@microsoft.com>
> Subject: Re: [PATCH] block: loose check on sg gap
> 
> On Wed, Jan 11, 2017 at 1:10 PM, Dexuan Cui <decui@microsoft.com> wrote:
> >> From: Dexuan Cui
> >> Sent: Tuesday, December 20, 2016 11:41
> >> To: 'Jens Axboe' <axboe@fb.com>; Ming Lei <ming.lei@canonical.com>
> >> Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>; linux-block
> >> <linux-block@vger.kernel.org>; Christoph Hellwig <hch@infradead.org>;
> >> Vitaly Kuznetsov <vkuznets@redhat.com>; Keith Busch
> >> <keith.busch@intel.com>; Hannes Reinecke <hare@suse.de>; Mike
> Christie
> >> <mchristi@redhat.com>; Martin K. Petersen
> <martin.petersen@oracle.com>;
> >> Toshi Kani <toshi.kani@hpe.com>; Dan Williams
> <dan.j.williams@intel.com>;
> >> Damien Le Moal <damien.lemoal@hgst.com>
> >> Subject: RE: [PATCH] block: loose check on sg gap
> >>
> >> > From: Jens Axboe [mailto:axboe@fb.com]
> >> > Sent: Tuesday, December 20, 2016 10:31
> >> > To: Ming Lei <ming.lei@canonical.com>
> >> > Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>; linux-block
> >> <linux-
> >> > block@vger.kernel.org>; Christoph Hellwig <hch@infradead.org>;
> Dexuan
> >> Cui
> >> > <decui@microsoft.com>; Vitaly Kuznetsov <vkuznets@redhat.com>;
> Keith
> >> Busch
> >> > <keith.busch@intel.com>; Hannes Reinecke <hare@suse.de>; Mike
> Christie
> >> > <mchristi@redhat.com>; Martin K. Petersen
> >> <martin.petersen@oracle.com>;
> >> > Toshi Kani <toshi.kani@hpe.com>; Dan Williams
> >> <dan.j.williams@intel.com>;
> >> > Damien Le Moal <damien.lemoal@hgst.com>
> >> > Subject: Re: [PATCH] block: loose check on sg gap
> >> >
> >> > On 12/19/2016 07:07 PM, Ming Lei wrote:
> >> > > On Sun, Dec 18, 2016 at 12:49 AM, Jens Axboe <axboe@fb.com> wrote:
> >> > >> On 12/17/2016 03:49 AM, Ming Lei wrote:
> >> > >>> If the last bvec of the 1st bio and the 1st bvec of the next
> >> > >>> bio are contineous physically, and the latter can be merged
> >> > >>> to last segment of the 1st bio, we should think they don't
> >> > >>> violate sg gap(or virt boundary) limit.
> >> > >>>
> >> > >>> Both Vitaly and Dexuan reported lots of unmergeable small bios
> >> > >>> are observed when running mkfs on Hyper-V virtual storage, and
> >> > >>> performance becomes quite low, so this patch is figured out for
> >> > >>> fixing the performance issue.
> >> > >>>
> >> > >>> The same issue should exist on NVMe too sine it sets virt boundary
> >> too.
> >> > >>
> >> > >> It looks pretty reasonable to me. I'll queue it up for some testing,
> >> > >> changes like this always make me a little nervous.
> >> > >
> >> > > Understood.
> >> > >
> >> > > But given it is still in early stage of 4.10 cycle, seems fine to expose
> >> > > it now, and we should have enough time to fix it if there might be
> >> > > regressions.
> >> > >
> >> > > BTW, it passes my xfstest(ext4) over sata/NVMe.
> >> >
> >> > It's been fine here in testing, too. I'm not worried about performance
> >> > regressions, those we can always fix. Merging makes me worried about
> >> > corruption, and those regressions are much worse.
> >> >
> >> > Any reason we need to rush this? I'd be more comfortable pushing this
> to
> >> > 4.11, unless there are strong reasons this should make 4.10.
> >> >
> >> > --
> >> > Jens Axboe
> >>
> >> Hi Jens,
> >>
> >> As far as I know, the patch is important to popular Linux distros,
> >> e.g. at least Ubuntu 14.04.5, 16.x and RHEL 7.3, when they run on
> >> Hyper-V/Azure, because they can suffer from a pretty bad
> >> throughput/latency
> >> in some cases, e.g. mkfs.ext4 for a 100GB partition can take 8 minutes,
> but
> >> with the patch, it only takes 1 second.
> >>
> >> -- Dexuan
> >
> > Hi Ming, Jens,
> > Did you find any issue later when testing with the patch?
> >
> > May I know if it's possible to have it in 4.10 considering the above impact?
> >
> > Is it on some temporary branch of linux-block.git? Looks not.
> 
> Dexuan, Jens has said that this patch may land v4.11, so just wait a release
> and let it expose into more tests.
> 
> Thanks,
> Ming

Thanks for the reply!

Sorry, I didn't mean to be pushy -- I just wanted to get more idea about the
status of the patch, since I'm unfamiliar with the linux-block repo. :-)

BTW, I've been using the patch for ~1 month and I didn't get any issue.

Thanks,
-- Dexuan

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