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Date:   Tue, 11 May 2021 10:13:06 +0800
From:   Oliver Sang <oliver.sang@intel.com>
To:     Roman Gushchin <guro@fb.com>
Cc:     Dennis Zhou <dennis@kernel.org>,
        Pratik Sampat <psampat@linux.ibm.com>,
        LKML <linux-kernel@vger.kernel.org>,
        "lkp@lists.01.org" <lkp@lists.01.org>,
        "lkp@intel.com" <lkp@intel.com>,
        "ying.huang@intel.com" <ying.huang@intel.com>,
        "feng.tang@intel.com" <feng.tang@intel.com>,
        "zhengjun.xing@intel.com" <zhengjun.xing@intel.com>
Subject: Re: [percpu]  ace7e70901:  aim9.sync_disk_rw.ops_per_sec -2.3%
 regression
Message-ID: <20210511021306.GA8539@xsang-OptiPlex-9020>
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Hi Roman,

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!

sorry for late. according to our tests, the answer seems be yes.
let me explain our test a little, we found the KPI (here is aim9)
droped, then an automatic bisection was triggered. the ace7e70901
was finally recognized as the commit introduced the change.

since it's a bisection result, we have test data for both parent
and this commit. (BTW, we make sure the config for both kernels are
same)

for this bisect, we tested 6 times for both parent and ace7e70901,
and the data is stable, as below:

parent:
f183324133ea535db4127f9fad3e19725ca88bf3/avg.json:  "aim9.sync_disk_rw.ops_per_sec": 103531.76166666666,

f183324133ea535db4127f9fad3e19725ca88bf3/matrix.json:  "aim9.sync_disk_rw.ops_per_sec": [
f183324133ea535db4127f9fad3e19725ca88bf3/matrix.json-    103673.09,
f183324133ea535db4127f9fad3e19725ca88bf3/matrix.json-    102188.39,
f183324133ea535db4127f9fad3e19725ca88bf3/matrix.json-    104325.06,
f183324133ea535db4127f9fad3e19725ca88bf3/matrix.json-    104038.4,
f183324133ea535db4127f9fad3e19725ca88bf3/matrix.json-    102908.57,
f183324133ea535db4127f9fad3e19725ca88bf3/matrix.json-    104057.06
f183324133ea535db4127f9fad3e19725ca88bf3/matrix.json-  ],

ace7e70901:
ace7e7090137ee996757eb5eebc94439b0e2803a/avg.json:  "aim9.sync_disk_rw.ops_per_sec": 101102.73857142858,

ace7e7090137ee996757eb5eebc94439b0e2803a/matrix.json:  "aim9.sync_disk_rw.ops_per_sec": [
ace7e7090137ee996757eb5eebc94439b0e2803a/matrix.json-    101193.43,
ace7e7090137ee996757eb5eebc94439b0e2803a/matrix.json-    100689.98,
ace7e7090137ee996757eb5eebc94439b0e2803a/matrix.json-    100988.63,
ace7e7090137ee996757eb5eebc94439b0e2803a/matrix.json-    100732.64,
ace7e7090137ee996757eb5eebc94439b0e2803a/matrix.json-    101389.69,
ace7e7090137ee996757eb5eebc94439b0e2803a/matrix.json-    101662.74,
ace7e7090137ee996757eb5eebc94439b0e2803a/matrix.json-    101062.06
ace7e7090137ee996757eb5eebc94439b0e2803a/matrix.json-  ],