> 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. Thanks, -- Dexuan
