linux-kernel - Re: [PATCH v2 11/27] perf parse-events: Support hardware events inside PMU

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Date:   Wed, 17 Mar 2021 10:12:03 +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 v2 11/27] perf parse-events: Support hardware events
 inside PMU



On 3/16/2021 10:04 PM, Jiri Olsa wrote:
> On Tue, Mar 16, 2021 at 09:49:42AM +0800, Jin, Yao wrote:
> 
> SNIP
> 
>>
>>   Performance counter stats for 'system wide':
>>
>>         136,655,302      cpu_core/branch-instructions/
>>
>>         1.003171561 seconds time elapsed
>>
>> So we need special rules for both cycles and branches.
>>
>> The worse thing is, we also need to process the hardware cache events.
>>
>> # ./perf stat -e cpu_core/LLC-loads/
>> event syntax error: 'cpu_core/LLC-loads/'
>>                                \___ unknown term 'LLC-loads' for pmu 'cpu_core'
>>
>> valid terms: event,pc,edge,offcore_rsp,ldlat,inv,umask,frontend,cmask,config,config1,config2,name,period,percore
>>
>> Initial error:
>> event syntax error: 'cpu_core/LLC-loads/'
>>                                \___ unknown term 'LLC-loads' for pmu 'cpu_core'
>>
>> If we use special rules for establishing all event mapping, that looks too much. :(
> 
> hmmm but wait, currently we do not support events like this:
> 
>    'cpu/cycles/'
>    'cpu/branches/'
> 
> the pmu style accepts only 'events' or 'format' terms within //
> 
> we made hw events like 'cycles','instructions','branches' special
> to be used without the pmu
> 
> so why do we need to support cpu_code/cycles/ ?
> 
> jirka
> 

Actually we have to support pmu style event for hybrid platform.

User may want to enable the events from specified pmus and also with flexible grouping.

For example,

perf stat -e '{cpu_core/cycles/,cpu_core/instructions/}' -e '{cpu_atom/cycles/,cpu_atom/instructions/}'

This usage is common and reasonable. So I think we may need to support pmu style events.

Thanks
Jin Yao