linux-kernel - Re: [PATCH v2 9/11] perf c2c: Sort on peer snooping for load operations

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Message-ID: <20220522132752.GC715382@leoy-ThinkPad-X240s>
Date:   Sun, 22 May 2022 21:27:52 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Adam Li <adamli@...amperecomputing.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Like Xu <likexu@...cent.com>, Ian Rogers <irogers@...gle.com>,
        Alyssa Ross <hi@...ssa.is>, Kajol Jain <kjain@...ux.ibm.com>,
        Li Huafei <lihuafei1@...wei.com>,
        German Gomez <german.gomez@....com>,
        James Clark <james.clark@....com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Ali Saidi <alisaidi@...zon.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 9/11] perf c2c: Sort on peer snooping for load
 operations

On Thu, May 19, 2022 at 05:06:18PM +0800, Adam Li wrote:
> Hi Leo,
> 
> Thanks for the update.
> On 5/18/2022 2:12 PM, Leo Yan wrote:
>  
> > Please note, in the total statistics, all remote accesses will be
> > accounted into metric "rmt_hit", so "rmt_hit" includes the access for
> > remote DRAM or any upwards cache levels due we cannot distinguish
> > them.
> >
> 
> Agree that "Load Remote HIT" makes more sense than "Load Remote DRAM".
>  
> > From my experiment, with this updating the output result is promised
> > for the peer accesses and it's easier for inspecting false sharing.
> > 
> > As you might see I have prepared a git repo:
> > https://git.linaro.org/people/leo.yan/linux-spe.git/ branch:
> > perf_c2c_arm_spe_peer_v3, which contains the updated patches for both
> > memory flag setting and perf c2c related patches.
> > 
> > Could you confirm if the updated code works for you or not?
> > 
> 
> I tested v3 patch (perf_c2c_arm_spe_peer_v3 branch) on 2P Altra system.
> 
> Compared with v2, "Snoop Peer" can better indicate cache false-sharing,
> for the 'false_sharing.exe' test case.

Thanks a lot for the testing and confirmation, Adam.

I will update the patches based on the comments from Joe and James,
after get ready will send out the patch set and loop you.

Thanks,
Leo