linux-kernel - Re: [PATCH] perf stat: Show percore counts in per CPU output

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Date:   Mon, 10 Feb 2020 21:46:46 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.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] perf stat: Show percore counts in per CPU output



On 2/10/2020 9:28 PM, Jiri Olsa wrote:
> On Thu, Feb 06, 2020 at 09:56:13AM +0800, Jin Yao wrote:
>> We have supported the event modifier "percore" which sums up the
>> event counts for all hardware threads in a core and show the counts
>> per core.
>>
>> For example,
>>
>>   # perf stat -e cpu/event=cpu-cycles,percore/ -a -A -- sleep 1
>>
>>    Performance counter stats for 'system wide':
>>
>>   S0-D0-C0                395,072      cpu/event=cpu-cycles,percore/
>>   S0-D0-C1                851,248      cpu/event=cpu-cycles,percore/
>>   S0-D0-C2                954,226      cpu/event=cpu-cycles,percore/
>>   S0-D0-C3              1,233,659      cpu/event=cpu-cycles,percore/
>>
>> This patch provides a new option "--percore-show-thread". It is
>> used with event modifier "percore" together to sum up the event counts
>> for all hardware threads in a core but show the counts per hardware
>> thread.
>>
>> For example,
>>
>>   # perf stat -e cpu/event=cpu-cycles,percore/ -a -A --percore-show-thread  -- sleep 1
>>
>>    Performance counter stats for 'system wide':
>>
>>   CPU0               2,453,061      cpu/event=cpu-cycles,percore/
>>   CPU1               1,823,921      cpu/event=cpu-cycles,percore/
>>   CPU2               1,383,166      cpu/event=cpu-cycles,percore/
>>   CPU3               1,102,652      cpu/event=cpu-cycles,percore/
>>   CPU4               2,453,061      cpu/event=cpu-cycles,percore/
>>   CPU5               1,823,921      cpu/event=cpu-cycles,percore/
>>   CPU6               1,383,166      cpu/event=cpu-cycles,percore/
>>   CPU7               1,102,652      cpu/event=cpu-cycles,percore/
> 
> I don't understand how is this different from -A output:
> 
>    # ./perf stat -e cpu/event=cpu-cycles/ -A
>    ^C
>     Performance counter stats for 'system wide':
> 
>    CPU0              56,847,497      cpu/event=cpu-cycles/
>    CPU1              75,274,384      cpu/event=cpu-cycles/
>    CPU2              63,866,342      cpu/event=cpu-cycles/
>    CPU3              89,559,693      cpu/event=cpu-cycles/
>    CPU4              74,761,132      cpu/event=cpu-cycles/
>    CPU5              76,320,191      cpu/event=cpu-cycles/
>    CPU6              55,100,175      cpu/event=cpu-cycles/
>    CPU7              48,472,895      cpu/event=cpu-cycles/
> 
>         1.074800857 seconds time elapsed
> 

The results are different.

With --percore-show-thread, CPU0 and CPU4 have the same counts (CPU0 and 
CPU4 are siblings, e.g. 2,453,061 in my example). The value is sum of 
CPU0 + CPU4.

Without --percore-show-thread, CPU0 and CPU4 have their own counts.

> also the interval output is mangled:
> 
>    # ./perf stat -e cpu/event=cpu-cycles,percore/ -a -A --percore-show-thread  -I 1000
>    #           time CPU                    counts unit events
>       1.000177375      1.000177375 CPU0             138,483,540      cpu/event=cpu-cycles,percore/
>       1.000177375      1.000177375 CPU1             143,159,477      cpu/event=cpu-cycles,percore/
>       1.000177375      1.000177375 CPU2             177,554,642      cpu/event=cpu-cycles,percore/
>       1.000177375      1.000177375 CPU3             150,974,512      cpu/event=cpu-cycles,percore/
>       1.000177375      1.000177375 CPU4             138,483,540      cpu/event=cpu-cycles,percore/
>       1.000177375      1.000177375 CPU5             143,159,477      cpu/event=cpu-cycles,percore/
>       1.000177375      1.000177375 CPU6             177,554,642      cpu/event=cpu-cycles,percore/
> 
> jirka
> 

Sorry, why the interval output is mangled? It's expected that CPU0 and 
CPU4 have the same counts.

Thanks
Jin Yao