linux-kernel - Re: [percpu] ace7e70901: aim9.sync_disk_rw.ops_per

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Date:   Tue, 11 May 2021 10:26:14 +0800
From:   Oliver Sang <oliver.sang@...el.com>
To:     Dennis Zhou <dennis@...nel.org>
Cc:     Roman Gushchin <guro@...com>,
        Pratik Sampat <psampat@...ux.ibm.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "lkp@...ts.01.org" <lkp@...ts.01.org>,
        "lkp@...el.com" <lkp@...el.com>,
        "ying.huang@...el.com" <ying.huang@...el.com>,
        "feng.tang@...el.com" <feng.tang@...el.com>,
        "zhengjun.xing@...el.com" <zhengjun.xing@...el.com>
Subject: Re: [percpu]  ace7e70901:  aim9.sync_disk_rw.ops_per_sec -2.3%
 regression

Hi Dennis,

On Fri, May 07, 2021 at 07:08:03PM +0000, Dennis Zhou wrote:
> On Fri, May 07, 2021 at 10:52:22AM -0700, Roman Gushchin wrote:
> > On Fri, May 07, 2021 at 11:06:06AM +0800, Oliver Sang wrote:
> > > hi Roman,
> > >  
> > > On Thu, May 06, 2021 at 12:54:59AM +0000, Roman Gushchin wrote:
> > > > Ping
> > > 
> > > sorry for late.
> > > 
> > > the new patch makes the performance a little better but still has
> > > 1.9% regression comparing to
> > > f183324133 ("percpu: implement partial chunk depopulation")
> > 
> > Hi Oliver!
> > 
> > Thank you for testing it!
> > 
> > Btw, can you, please, confirm that the regression is coming specifically
> > from ace7e70901 ("percpu: use reclaim threshold instead of running for every page")?
> > I do see *some* regression in my setup, but the data is very noisy, so I'm not sure
> > I can confirm it.
> > 
> > Thanks!
> 
> Thanks Oliver and Roman. If this is the case, I'll drop the final patch
> and just merge up to f183324133 ("percpu: implement partial chunk
> depopulation") into for-next as this is v5.14 anyway.
> 
> Oliver, is there a way to trigger the kernel test robot for a specific
> test?

sorry for late.
not sure what kind of specific test you want robot to do?
if you mean for-next branch, if the branch is monitored by kernel test robot,
after merge, it will be tested by robot automatically and the bisect will be
triggered if there is still regression.

I found the ace7e70901 has already been dropped from original branch (dennis-percpu/for-5.14),
and we have data for this branch as below. from data, the f183324133 (current
branch tip) doesn't introduce regression comparing 5.12-rc7 in our tests.

f183324133ea5 percpu: implement partial chunk depopulation                 103673.09 102188.39 104325.06 104038.4 102908.57 104057.06
1c29a3ceaf5f0 percpu: use pcpu_free_slot instead of pcpu_nr_slots - 1      104777.31 102225.93 101657.6
8ea2e1e35d1eb percpu: factor out pcpu_check_block_hint()                   102290.78 101853.87 102541.65
d434405aaab7d Linux 5.12-rc7                                               102103.06 102248.12 101906.81 103033.13 102043.33


> 
> Thanks,
> Dennis