> From: Ming Lei [mailto:ming.lei@xxxxxxxxxxxxx] > Sent: Thursday, January 12, 2017 10:54 > To: Dexuan Cui <decui@xxxxxxxxxxxxx> > Cc: Jens Axboe <axboe@xxxxxx>; Linux Kernel Mailing List <linux- > kernel@xxxxxxxxxxxxxxx>; linux-block <linux-block@xxxxxxxxxxxxxxx>; > Christoph Hellwig <hch@xxxxxxxxxxxxx>; Vitaly Kuznetsov > <vkuznets@xxxxxxxxxx>; Keith Busch <keith.busch@xxxxxxxxx>; Hannes > Reinecke <hare@xxxxxxx>; Mike Christie <mchristi@xxxxxxxxxx>; Martin K. > Petersen <martin.petersen@xxxxxxxxxx>; Toshi Kani <toshi.kani@xxxxxxx>; > Dan Williams <dan.j.williams@xxxxxxxxx>; Damien Le Moal > <damien.lemoal@xxxxxxxx>; KY Srinivasan <kys@xxxxxxxxxxxxx> > Subject: Re: [PATCH] block: loose check on sg gap > > On Wed, Jan 11, 2017 at 1:10 PM, Dexuan Cui <decui@xxxxxxxxxxxxx> wrote: > >> From: Dexuan Cui > >> Sent: Tuesday, December 20, 2016 11:41 > >> To: 'Jens Axboe' <axboe@xxxxxx>; Ming Lei <ming.lei@xxxxxxxxxxxxx> > >> Cc: Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>; linux-block > >> <linux-block@xxxxxxxxxxxxxxx>; Christoph Hellwig <hch@xxxxxxxxxxxxx>; > >> Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>; Keith Busch > >> <keith.busch@xxxxxxxxx>; Hannes Reinecke <hare@xxxxxxx>; Mike > Christie > >> <mchristi@xxxxxxxxxx>; Martin K. Petersen > <martin.petersen@xxxxxxxxxx>; > >> Toshi Kani <toshi.kani@xxxxxxx>; Dan Williams > <dan.j.williams@xxxxxxxxx>; > >> Damien Le Moal <damien.lemoal@xxxxxxxx> > >> Subject: RE: [PATCH] block: loose check on sg gap > >> > >> > From: Jens Axboe [mailto:axboe@xxxxxx] > >> > Sent: Tuesday, December 20, 2016 10:31 > >> > To: Ming Lei <ming.lei@xxxxxxxxxxxxx> > >> > Cc: Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>; linux-block > >> <linux- > >> > block@xxxxxxxxxxxxxxx>; Christoph Hellwig <hch@xxxxxxxxxxxxx>; > Dexuan > >> Cui > >> > <decui@xxxxxxxxxxxxx>; Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>; > Keith > >> Busch > >> > <keith.busch@xxxxxxxxx>; Hannes Reinecke <hare@xxxxxxx>; Mike > Christie > >> > <mchristi@xxxxxxxxxx>; Martin K. Petersen > >> <martin.petersen@xxxxxxxxxx>; > >> > Toshi Kani <toshi.kani@xxxxxxx>; Dan Williams > >> <dan.j.williams@xxxxxxxxx>; > >> > Damien Le Moal <damien.lemoal@xxxxxxxx> > >> > 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@xxxxxx> 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 ��.n��������+%������w��{.n�����{����n�r������&��z�ޗ�zf���h���~����������_��+v���)ߣ�
