linux-kernel - Re: [PATCH v3 0/3] perf report/annotate: Support average IPC and IPC coverage for function

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Date:   Wed, 28 Nov 2018 10:10:05 +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 v3 0/3] perf report/annotate: Support average IPC and IPC
 coverage for function


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

> Add supporting of displaying the average IPC and IPC coverage
> percentage per function.
> 
> For example,
> 
> $ perf record -b ...
> $ perf report -s symbol or
>   perf report -s symbol --stdio
> 
> Overhead  Symbol                           IPC   [IPC Coverage]
>   39.60%  [.] __random                     2.30  [ 54.8%]
>   18.02%  [.] main                         0.43  [ 54.3%]
>   14.21%  [.] compute_flag                 2.29  [100.0%]
>   14.16%  [.] rand                         0.36  [100.0%]
>    7.06%  [.] __random_r                   2.57  [ 70.5%]
>    6.85%  [.] rand@plt                     0.00  [  0.0%]
>   ...
> 
> $ perf annotate --stdio2
> 
> Percent  IPC Cycle (Average IPC: 2.30, IPC Coverage: 54.8%)
> 
>                         Disassembly of section .text:
> 
>                         000000000003aac0 <random@@GLIBC_2.2.5>:
>   8.32  3.28              sub    $0x18,%rsp
>         3.28              mov    $0x1,%esi
>         3.28              xor    %eax,%eax
>         3.28              cmpl   $0x0,argp_program_version_hook@@GLIBC_2.2.5+0x1e0
>  11.57  3.28     1      ↓ je     20
>                           lock   cmpxchg %esi,__abort_msg@@GLIBC_PRIVATE+0x8a0
>                         ↓ jne    29
>                         ↓ jmp    43
>  11.57  1.10        20:   cmpxchg %esi,__abort_msg@@GLIBC_PRIVATE+0x8a0

That's a nice feature: please add meaningful documentation, accessible 
via the perf help system preferably, that outlines how the IPC metrics 
should be interpreted and how they are useful when optimizing programs.

Thanks,

	Ingo