linux-kernel - Re: [PATCH v4 4/4] perf report: Documentation average IPC and IPC coverage

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Date:   Thu, 29 Nov 2018 14:27:46 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Jin Yao <yao.jin@...ux.intel.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH v4 4/4] perf report: Documentation average IPC and IPC
 coverage


* Jin Yao <yao.jin@...ux.intel.com> wrote:

> Add explanations for new columns "IPC" and "IPC coverage" in perf
> documentation.
> 
> Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
> ---
>  tools/perf/Documentation/perf-report.txt | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/tools/perf/Documentation/perf-report.txt b/tools/perf/Documentation/perf-report.txt
> index 474a494..e5a32f3 100644
> --- a/tools/perf/Documentation/perf-report.txt
> +++ b/tools/perf/Documentation/perf-report.txt
> @@ -126,6 +126,14 @@ OPTIONS
>  	And default sort keys are changed to comm, dso_from, symbol_from, dso_to
>  	and symbol_to, see '--branch-stack'.
>  
> +	When the sort key symbol is specified, columns "IPC" and "IPC Coverage"
> +	are enabled automatically. Column "IPC" reports the average IPC per function
> +	and column "IPC coverage" reports the percentage of instructions with
> +	sampled IPC in this function. IPC means Instruction Per Cycle. If it's low,
> +	it indicates there may be performance bottleneck when the function is
> +	executed, such as, memory access bottleneck. If a function has high overhead
> +	and low IPC, it's worth further analysis for performance optimization.

Thank you for adding this!

Just a few small nits:

s/may be performance bottleneck
 /may be a performance bottleneck

s/such as, memory access bottleneck
 /such as a memory access bottleneck

s/it's worth further analysis for performance optimization.
 /it's worth further analyzing it to optimize its performance.

?

Other than that:

Reviewed-by: Ingo Molnar <mingo@...nel.org>

	Ingo