RE: RE: very low IOPS due to "block: reduce kblockd_mod_delayed_work_on() CPU consumption"

[Dexuan Cui]

> From: Dexuan Cui
> Sent: Friday, January 21, 2022 10:15 PM
> To: Oliver Sang <oliver.sang@xxxxxxxxx>; Jens Axboe <axboe@xxxxxxxxx>; Yin
> Fengwei <fengwei.yin@xxxxxxxxx>; linux-block@xxxxxxxxxxxxxxx
> Cc: Alex Xu (Hello71) <alex_y_xu@xxxxxxxx>; ming.lei@xxxxxxxxxx;
> hch@xxxxxx; Long Li <longli@xxxxxxxxxxxxx>; Michael Kelley (LINUX)
> <mikelley@xxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; Li, Philip
> <philip.li@xxxxxxxxx>; Rakesh Ginjupalli <Rakesh.Ginjupalli@xxxxxxxxxxxxx>
> Subject: RE: RE: very low IOPS due to "block: reduce
> kblockd_mod_delayed_work_on() CPU consumption"
> 
> > From: Oliver Sang <oliver.sang@xxxxxxxxx>
> > Sent: Tuesday, December 28, 2021 5:49 AM
> >  ...
> > Hi Jens, Dexuan,
> >
> > On Tue, Dec 28, 2021 at 10:30:43AM +0800, Yin Fengwei wrote:
> > > Hi Jens, Dexuan,
> > >
> > > On 12/20/2021 1:15 PM, Dexuan Cui wrote:
> > > >> From: Jens Axboe <axboe@xxxxxxxxx>
> > > >> Sent: Sunday, December 19, 2021 7:28 AM
> > > >>> ...
> > > >>> Dexuan, can you test this for your test case too? I'm going to queue
> > > >>> up a revert for -rc6 just in case.
> > > >>
> > > >> This one should be better...
> > > >> ...
> > > >> Jens Axboe
> > > >
> > > > Hi Jens, sorry -- unluckily I lost the test environment.. :-(
> > > > I pinged the user to set up the test environment again, but he's
> > > > on vacation till the beginning of January.
> > >
> > > We hit this issue in our testing env also and will help to verify
> > > your fixing patch. Thanks.
> >
> > as we reported in [1], we found cb2ac2912a cause big regressions in fxmark
> > tests.
> > "[block]  cb2ac2912a:
> > fxmark.ssd_f2fs_dbench_client_4_bufferedio.works/sec -66.0% regression"
> >
> > By applying the patch supplied by Jens Axboe in previous thread directly
> > upon cb2ac2912a, we confirmed the regression could be fixed:
> > ...
> > > Regards
> > > Yin, Fengwei
> 
> Hi Jens, Fengwei,
> I finally regained my test evnironment and tested Jens's Dec-19 patch
> (see https://www.spinics.net/lists/linux-block/msg78065.html) and it
> also worked fine for me, i.e. no excessive CPU utilization even with the
> default dm_mod.dm_mq_queue_depth=2048.
> 
> BTW, Jen's patch is not in the mainline yet. I tested it using the linux-block tree.
> 
> Thanks,
> -- Dexuan

Hi Jens, any plan to commit your 12/19/2021 patch? 
It works great according to Fengwei's and my test.