linux-kernel - Re: [PATCH] tracing: Allow perf to read synthetic events

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Message-ID: <20251217140816.23a8a1bc@gandalf.local.home>
Date: Wed, 17 Dec 2025 14:08:16 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Ian Rogers <irogers@...gle.com>
Cc: LKML <linux-kernel@...r.kernel.org>, Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] tracing: Allow perf to read synthetic events

On Wed, 17 Dec 2025 10:58:25 -0800
Ian Rogers <irogers@...gle.com> wrote:

> This is great! Any chance of an example of using it? I'd like to add a test.

I tested it with:

  # trace-cmd sqlhist -e -n futex_wait select TIMESTAMP_DELTA_USECS as lat from sys_enter_futex as start join sys_exit_futex as end on start.common_pid = end.common_pid
  # perf record -e synthetic:futex_wait
  # perf script
            bash    1043 [002]    49.501707: synthetic:futex_wait: lat=8
     in:imuxsock     610 [005]    58.904344: synthetic:futex_wait: lat=27
   rs:main Q:Reg     612 [007]    58.904478: synthetic:futex_wait: lat=10847333
   rs:main Q:Reg     612 [007]    58.904507: synthetic:futex_wait: lat=6
              ls    1050 [004]    59.283561: synthetic:futex_wait: lat=8
       in:imklog     611 [004]    69.084959: synthetic:futex_wait: lat=55
   rs:main Q:Reg     612 [007]    69.085014: synthetic:futex_wait: lat=10180378
   rs:main Q:Reg     612 [007]    69.085041: synthetic:futex_wait: lat=5


But feel free to use any other synthetic event or perf command.

-- Steve