linux-kernel - Re: [PATCH v1 0/8] perf c2c: Refine the organization of metrics

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Date:   Wed, 14 Oct 2020 14:38:19 -0400
From:   Joe Mario <jmario@...hat.com>
To:     Leo Yan <leo.yan@...aro.org>,
        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@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        David Ahern <dsahern@...il.com>,
        Don Zickus <dzickus@...hat.com>, Al Grant <Al.Grant@....com>,
        James Clark <james.clark@....com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 0/8] perf c2c: Refine the organization of metrics



On 10/14/20 1:09 AM, Leo Yan wrote:
> This patch set is to refine metrics output organization.
> 
> If we reivew the current memory metrics in Perf c2c tool, it doesn't
> orgnize the metrics with directive approach; thus user needs to take
> time to dig into every statistics item.  On the other hand, if use the
> "summary and breakdown" approach, the output result will be easier for
> reviewing by users, e.g. the output result can firstly give out the
> summary values, and then the later items will breakdown into more
> detailed statistics.
> 
> For this reason, this patch is to reorgnize the metrics and it only
> changes for the "Shared Data Cache Line Table": it firstly displays the
> summary values for total records, total loads, total stores; then it
> breaks these summary values into small values, with the order from the
> most near memory node ("CPU Load Hit") to more far nodes
> ("LLC Load Hit", "RMT Load Hit", "Load Dram").
> 
>   "LLC Load Hit" = "LclHit" + "LclHitm"
> 
>   "RMT Load Hit" = "RmtHit" + "RmtHitm" \
>                                          ->  LLC Load Miss
>   "Load Dram"    = "Lcl" + "Rmt"        /
> 
> Another main reason for this patch set is wanting to extend "perf c2c"
> to support Arm SPE memory event, but Arm SPE doesn't contain 'HTIM' tag
> in its default trace data, for this case if want to analyze cache false
> sharing issue, we need to rely on LLC metrics + multi-threading info.
> So this patch set can be friendly to show LLC related metrics in the
> "Shared Data Cache Line Table"; for sorting cache lines with LLC metrics
> which will be sent out with another separate patch set.
> 
> <SNIP>
> 
> Leo Yan (8):
>   perf c2c: Display the total numbers continuously
>   perf c2c: Display "Total Stores" as a standalone metrics
>   perf c2c: Organize metrics based on memory hierarchy
>   perf c2c: Change header from "LLC Load Hitm" to "Load Hitm"
>   perf c2c: Use more explicit headers for HITM
>   perf c2c: Change header for LLC local hit
>   perf c2c: Correct LLC load hit metrics
>   perf c2c: Add metrics "RMT Load Hit"
> 
>  tools/perf/builtin-c2c.c | 83 +++++++++-------------------------------
>  1 file changed, 18 insertions(+), 65 deletions(-)

Hi Leo:
I ran your patches through some perf c2c tests and it all looks good.  
I agree the new format of the "Shared Data Cache Line Table" makes more sense now.  And it still holds together nicely when sorted on local HitMs (-d lcl).

Thank you for doing this.
Joe

Tested-by: Joe Mario <jmario@...hat.com>