Date:   Fri, 11 Oct 2019 10:50:35 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc:     Jiri Olsa <jolsa@...hat.com>, Andi Kleen <ak@...ux.intel.com>,
        jolsa@...nel.org, peterz@...radead.org, mingo@...hat.com,
        alexander.shishkin@...ux.intel.com, Linux-kernel@...r.kernel.org,
        kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH v1 0/2] perf stat: Support --all-kernel and --all-user



On 10/10/2019 8:33 PM, Arnaldo Carvalho de Melo wrote:
> Em Thu, Oct 10, 2019 at 04:33:57PM +0800, Jin, Yao escreveu:
>>
>>
>> On 10/10/2019 4:00 PM, Jiri Olsa wrote:
>>> On Thu, Oct 10, 2019 at 02:46:36PM +0800, Jin, Yao wrote:
>>>>
>>>>
>>>> On 10/1/2019 10:17 AM, Andi Kleen wrote:
>>>>>>> I think it's useful. Makes it easy to do kernel/user break downs.
>>>>>>> perf record should support the same.
>>>>>>
>>>>>> Don't we have this already with:
>>>>>>
>>>>>> [root@...co ~]# perf stat -e cycles:u,instructions:u,cycles:k,instructions:k -a -- sleep 1
>>>>>
>>>>> This only works for simple cases. Try it for --topdown or multiple -M metrics.
>>>>>
>>>>> -Andi
>>>>>
>>>>
>>>> Hi Arnaldo, Jiri,
>>>>
>>>> We think it should be very useful if --all-user / --all-kernel can be
>>>> specified together, so that we can get a break down between user and kernel
>>>> easily.
>>>>
>>>> But yes, the patches for supporting this new semantics is much complicated
>>>> than the patch which just follows original perf-record behavior. I fully
>>>> understand this concern.
>>>>
>>>> So if this new semantics can be accepted, that would be very good. But if
>>>> you think the new semantics is too complicated, I'm also fine for posting a
>>>> new patch which just follows the perf-record behavior.
>>>
>>> I still need to think a bit more about this.. did you consider
>>> other options like cloning of the perf_evlist/perf_evsel and
>>> changing just the exclude* bits? might be event worse actualy ;-)
>>>
>>
>> That should be another approach, but it might be a bit more complicated than
>> just appending ":u"/":k" modifiers to the event name string.
>>
>>> or maybe if we add modifier we could add extra events/groups
>>> within the parser.. like:
>>>
>>>     "{cycles,instructions}:A,{cache-misses,cache-references}:A,cycles:A"
>>>
>>> but that might be still more complicated then what you did
>>>
>>
>> Yes agree.
>>
>>> also please add the perf record changes so we have same code
>>> and logic for both if we are going to change it
>   
>> If this new semantics can be accepted, I'd like to add perf record
>> supporting as well. :)
> 
> Changes in semantics should be avoided, when we add an option already
> present in some other tool, we should strive to keep the semantics, so
> that people can reuse their knowledge and just switch tools to go from
> sampling to counting, say.
>

Yes, that makes sense. We need to try our best to keep the original 
semantics. I will post a patch for perf-stat which just follows the 
semantics in perf-record.

> So if at all possible, and without having really looked deep in this
> specific case, I would prefer that new semantics come with a new syntax,
> would that be possible?
> 

Yes, that's possible. Maybe we can use a new option for automatically 
adding two copies of the events (one copy for user and the other copy 
for kernel). The option something like "--all-space"?

Thanks
Jin Yao

> - Arnaldo
>   



>> Another difficulty for the new semantics is we need to create user and
>> kernel stat type in runtime_stat rblist (see patch "perf stat: Support
>> topdown with --all-kernel/--all-user"). That has to bring extra complexity.
>>
>> Thanks
>> Jin Yao
>>
>>> jirka
>>>
> 

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