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Date: Tue, 09 Jan 2024 17:01:59 -0800
From: Kees Cook <kees@kernel.org>
To: Namhyung Kim <namhyung@kernel.org>
CC: linux-perf-users@vger.kernel.org
Subject: Re: Getting PMU stats on specific syscalls
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On January 9, 2024 3:52:53 PM PST, Namhyung Kim <namhyung@kernel=2Eorg> wr=
ote:
>Hello,
>
>On Tue, Jan 9, 2024 at 2:56=E2=80=AFPM Kees Cook <keescook@chromium=2Eorg=
> wrote:
>>
>> Hi,
>>
>> I'd like to get PMU stats only on specific syscalls=2E I haven't been a=
ble
>> to figure this out=2E i=2Ee=2E how do I run:
>>
>>         perf stat -e some_syscall_name_here make -j128
>
>How about this?
>
>  perf stat -e syscalls:sys_enter_<syscall_name> -- make -j128

Unfortunately this is just a count of calls=2E

>
>>
>> I can't figure out how to limit collection to only time spent during th=
e
>> syscall I'm interested in=2E I tried building synthetic events, but tha=
t
>> doesn't seem to work=2E=2E=2E
>
>Hmm=2E=2E ok=2E  it seems you want to use PMU only for a syscall=2E
>I don't think perf supports that for now, but maybe it's possible
>to attach custom BPF programs to read perf counters at syscall
>enter and exit and to save the diff in a map=2E

Does BPF have access to the PMU counters? I don't know how to even approac=
h writing that though=2E :P

--=20
Kees Cook