linux-kernel - Re: [RFC][PATCH 03/16] sched: Wrap rq::lock access

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Date:   Thu, 4 Apr 2019 18:30:45 -0700
From:   Subhra Mazumdar <subhra.mazumdar@...cle.com>
To:     Julien Desfossez <jdesfossez@...italocean.com>
Cc:     Peter Zijlstra <peterz@...radead.org>, mingo@...nel.org,
        tglx@...utronix.de, pjt@...gle.com, tim.c.chen@...ux.intel.com,
        torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
        fweisbec@...il.com, keescook@...omium.org, kerrnel@...gle.com,
        Vineeth Pillai <vpillai@...italocean.com>,
        Nishanth Aravamudan <naravamudan@...italocean.com>
Subject: Re: [RFC][PATCH 03/16] sched: Wrap rq::lock access


> We tried to comment those lines and it doesn’t seem to get rid of the
> performance regression we are seeing.
> Can you elaborate a bit more about the test you are performing, what kind of
> resources it uses ?
I am running 1 and 2 Oracle DB instances each running TPC-C workload. The
clients driving the instances also run in same node. Each server client
pair is put in each cpu group and tagged.
> Can you also try to replicate our test and see if you see the same problem ?
>
> cgcreate -g cpu,cpuset:set1
> cat /sys/devices/system/cpu/cpu{0,2,4,6}/topology/thread_siblings_list
> 0,36
> 2,38
> 4,40
> 6,42
>
> echo "0,2,4,6,36,38,40,42" | sudo tee /sys/fs/cgroup/cpuset/set1/cpuset.cpus
> echo 0 | sudo tee /sys/fs/cgroup/cpuset/set1/cpuset.mems
>
> echo 1 | sudo tee /sys/fs/cgroup/cpu,cpuacct/set1/cpu.tag
>
> sysbench --test=fileio prepare
> cgexec -g cpu,cpuset:set1 sysbench --threads=4 --test=fileio \
> --file-test-mode=seqwr run
>
> The reason we create a cpuset is to narrow down the investigation to just 4
> cores on a highly powerful machine. It might not be needed if testing on a
> smaller machine.
With this sysbench test I am not seeing any improvement with removing the
condition. Also with hackbench I found it makes no difference but that has
much lower regression to begin with (18%)
>
> Julien