linux-kernel - Re: [External] Re: [RFC 00/12] perf record: Add event action support

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Message-ID: <663c3133-12ea-4bc8-b30c-c925d7e86bf6@bytedance.com>
Date: Wed, 4 Dec 2024 16:07:47 +0800
From: Yang Jihong <yangjihong@...edance.com>
To: Adrian Hunter <adrian.hunter@...el.com>, peterz@...radead.org,
 mingo@...hat.com, acme@...nel.org, namhyung@...nel.org,
 mark.rutland@....com, alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
 irogers@...gle.com, kan.liang@...ux.intel.com, james.clark@....com,
 linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [External] Re: [RFC 00/12] perf record: Add event action support

Hello,

On 11/28/24 21:53, Adrian Hunter wrote:
> On 28/11/24 15:35, Yang Jihong wrote:
>> In perf-record, when an event is triggered, default behavior is to
>> save sample data to perf.data. Sometimes, we may just want to do
>> some lightweight actions, such as printing a log.
> 
> Why not just pipe 'perf record' to 'perf script'?
> 
> # perf record -e sched:sched_switch | perf script | head
>              perf  768231 [000] 2318380.474267: sched:sched_switch: perf:768231 [120] R ==> migration/0:18 [0]
>       migration/0      18 [000] 2318380.474294: sched:sched_switch: migration/0:18 [0] S ==> swapper/0:0 [120]
>              perf  768231 [001] 2318380.474353: sched:sched_switch: perf:768231 [120] R ==> migration/1:23 [0]
>       migration/1      23 [001] 2318380.474382: sched:sched_switch: migration/1:23 [0] S ==> swapper/1:0 [120]
>              perf  768231 [002] 2318380.474477: sched:sched_switch: perf:768231 [120] R ==> migration/2:29 [0]
>       migration/2      29 [002] 2318380.474503: sched:sched_switch: migration/2:29 [0] S ==> swapper/2:0 [120]
>              perf  768231 [003] 2318380.474513: sched:sched_switch: perf:768231 [120] R ==> migration/3:35 [0]
>       migration/3      35 [003] 2318380.474523: sched:sched_switch: migration/3:35 [0] S ==> swapper/3:0 [120]
>              perf  768231 [004] 2318380.474534: sched:sched_switch: perf:768231 [120] R ==> migration/4:41 [0]
>       migration/4      41 [004] 2318380.474541: sched:sched_switch: migration/4:41 [0] S ==> swapper/4:0 [120]

pipe 'perf record' to 'perf script' has limited extensions.
We can use bpf prog to do more (such as saving user-defined data (such 
as registers, function parameters), and customizing the format of 
user-printed logs).

Now we only implement a simple print() call, and we can support more 
calls later.

Thanks,
Yang