linux-kernel - Re: [PATCH v2] perf stat: Append to default list if use -e +event

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Date:   Thu, 21 Jan 2021 13:05:36 +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] perf stat: Append to default list if use -e +event

Hi Jiri,

On 1/21/2021 5:25 AM, Jiri Olsa wrote:
> On Mon, Jan 18, 2021 at 12:54:37PM +0800, Jin, Yao wrote:
>> Hi Jiri,
>>
>> On 1/12/2021 6:08 PM, Jiri Olsa wrote:
>>> On Mon, Jan 04, 2021 at 10:18:37AM +0800, Jin Yao wrote:
>>>> The default event list includes the most common events which are widely
>>>> used by users. But with -e option, the current perf only counts the events
>>>> assigned by -e option. Users may want to collect some extra events with
>>>> the default list. For this case, users have to manually add all the events
>>>> from the default list. It's inconvenient. Also, users may don't know how to
>>>> get the default list.
>>>>
>>>> Now it supports a simple syntax: -e +event
>>>>
>>>> The prefix '+' tells perf to append this event (or event list) to default
>>>> event list.
>>>>
>>>> Before:
>>>>
>>>> root@...-ppc:~# ./perf stat -e power/energy-pkg/ -a -- sleep 1
>>>>
>>>>    Performance counter stats for 'system wide':
>>>>
>>>>                 2.04 Joules power/energy-pkg/
>>>>
>>>>          1.000863884 seconds time elapsed
>>>>
>>>> After:
>>>>
>>>> root@...-ppc:~# ./perf stat -e +power/energy-pkg/ -a -- sleep 1
>>>>
>>>>    Performance counter stats for 'system wide':
>>>>
>>>>                 2.11 Joules +power/energy-pkg/        #    0.000 K/sec
>>>
>>> I dont think we should print the extra '+' prefix
>>>
>>> jirka
>>>
>>>>             8,007.17 msec   cpu-clock                 #    7.993 CPUs utilized
>>>>                  125        context-switches          #    0.016 K/sec
>>>>                    8        cpu-migrations            #    0.001 K/sec
>>>>                    2        page-faults               #    0.000 K/sec
>>>>            8,520,084        cycles                    #    0.001 GHz
>>>>            2,808,302        instructions              #    0.33  insn per cycle
>>>>              555,427        branches                  #    0.069 M/sec
>>>>               59,005        branch-misses             #   10.62% of all branches
>>>>
>>>>          1.001832003 seconds time elapsed
>>>>
>>>> Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
>>>
>>
>> Printing '+' prefix is the original behavior.
>>
>> Without this patch,
>>
>> root@...-ppc:# ./perf stat -e +power/energy-pkg/ -a -- sleep 1
>>
>>   Performance counter stats for 'system wide':
>>
>>                2.02 Joules +power/energy-pkg/
>>
>>         1.000859434 seconds time elapsed
>>
>> The '+' prefix is printed. So I finally decide not to remove the '+' prefix
>> in order to keep original behavior.
> 
> hm, originaly there's no purpose for the '+', right?
> it seems it's more like bug then anything else
> 

Yes, I also don't understand what's the purpose for the '+'. Just a bug is possible.

> you added function to the '+' to add default events to specified event,
> which I think is good idea, but I don't think we should display the
> extra '+' in output
> 

I'm OK to remove the extra '+' in output.

Thanks
Jin Yao

> thanks,
> jirka
>