On Wed, Jan 11, 2017 at 1:10 PM, Dexuan Cui <[email protected]> wrote: >> From: Dexuan Cui >> Sent: Tuesday, December 20, 2016 11:41 >> To: 'Jens Axboe' <[email protected]>; Ming Lei <[email protected]> >> Cc: Linux Kernel Mailing List <[email protected]>; linux-block >> <[email protected]>; Christoph Hellwig <[email protected]>; >> Vitaly Kuznetsov <[email protected]>; Keith Busch >> <[email protected]>; Hannes Reinecke <[email protected]>; Mike Christie >> <[email protected]>; Martin K. Petersen <[email protected]>; >> Toshi Kani <[email protected]>; Dan Williams <[email protected]>; >> Damien Le Moal <[email protected]> >> Subject: RE: [PATCH] block: loose check on sg gap >> >> > From: Jens Axboe [mailto:[email protected]] >> > Sent: Tuesday, December 20, 2016 10:31 >> > To: Ming Lei <[email protected]> >> > Cc: Linux Kernel Mailing List <[email protected]>; linux-block >> <linux- >> > [email protected]>; Christoph Hellwig <[email protected]>; Dexuan >> Cui >> > <[email protected]>; Vitaly Kuznetsov <[email protected]>; Keith >> Busch >> > <[email protected]>; Hannes Reinecke <[email protected]>; Mike Christie >> > <[email protected]>; Martin K. Petersen >> <[email protected]>; >> > Toshi Kani <[email protected]>; Dan Williams >> <[email protected]>; >> > Damien Le Moal <[email protected]> >> > 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 <[email protected]> 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
