linux-kernel - Re: [PATCH] perf stat: Support per-cluster aggregation

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Date:   Tue, 28 Mar 2023 23:47:23 -0700
From:   Namhyung Kim <namhyung@...il.com>
To:     "Chen, Tim C" <tim.c.chen@...el.com>
Cc:     Yicong Yang <yangyicong@...wei.com>,
        "acme@...nel.org" <acme@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "james.clark@....com" <james.clark@....com>,
        "alexander.shishkin@...ux.intel.com" 
        <alexander.shishkin@...ux.intel.com>,
        "linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Jonathan.Cameron@...wei.com" <Jonathan.Cameron@...wei.com>,
        "21cnbao@...il.com" <21cnbao@...il.com>,
        "prime.zeng@...ilicon.com" <prime.zeng@...ilicon.com>,
        "shenyang39@...wei.com" <shenyang39@...wei.com>,
        "linuxarm@...wei.com" <linuxarm@...wei.com>,
        "yangyicong@...ilicon.com" <yangyicong@...ilicon.com>
Subject: Re: [PATCH] perf stat: Support per-cluster aggregation

Hello,

On Fri, Mar 24, 2023 at 11:09 AM Chen, Tim C <tim.c.chen@...el.com> wrote:
>
> >
> >From: Yicong Yang <yangyicong@...ilicon.com>
> >
> >Some platforms have 'cluster' topology and CPUs in the cluster will share
> >resources like L3 Cache Tag (for HiSilicon Kunpeng SoC) or L2 cache (for Intel
> >Jacobsville). Currently parsing and building cluster topology have been
> >supported since [1].
> >
> >perf stat has already supported aggregation for other topologies like die or
> >socket, etc. It'll be useful to aggregate per-cluster to find problems like L3T
> >bandwidth contention or imbalance.
> >
> >This patch adds support for "--per-cluster" option for per-cluster aggregation.
> >Also update the docs and related test. The output will be like:
> >
> >[root@...alhost tmp]# perf stat -a -e LLC-load --per-cluster -- sleep 5
> >
> > Performance counter stats for 'system wide':
> >
> >S56-D0-CLS158    4      1,321,521,570      LLC-load
> >S56-D0-CLS594    4        794,211,453      LLC-load
> >S56-D0-CLS1030    4             41,623      LLC-load
> >S56-D0-CLS1466    4             41,646      LLC-load
> >S56-D0-CLS1902    4             16,863      LLC-load
> >S56-D0-CLS2338    4             15,721      LLC-load
> >S56-D0-CLS2774    4             22,671      LLC-load
> >[...]
>
> Overall it looks good.  You can add my reviewed-by.
>
> I wonder if we could enhance the help message
> in perf stat to tell user to refer to
> /sys/devices/system/cpu/cpuX/topology/*_id
> to map relevant ids back to overall cpu topology.
>
> For example the above example, cluster S56-D0-CLS158  has
> really heavy load. It took me  a while
> going through the code to figure out how to find
> the info that maps cluster id to cpu.

Maybe we could enhance the cpu filter to accept something
like -C S56-D0-CLS158.

I also wonder what if it runs on an old kernel which doesn't
have the cluster_id file.

Thanks,
Namhyung