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Message-ID: <CAM9d7ciF+_s+MqNou4szVSStBObtB87UznMMG8SsZkuRyR1dNg@mail.gmail.com>
Date: Tue, 29 Dec 2020 14:53:36 +0900
From: Namhyung Kim <namhyung@...nel.org>
To: Jiri Olsa <jolsa@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
lkml <linux-kernel@...r.kernel.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Ingo Molnar <mingo@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Michael Petlan <mpetlan@...hat.com>,
Ian Rogers <irogers@...gle.com>,
Stephane Eranian <eranian@...gle.com>,
Alexei Budankov <abudankov@...wei.com>
Subject: Re: [PATCH] perf tools: Detect when pipe is passed as perf data
On Sat, Dec 26, 2020 at 7:21 AM Jiri Olsa <jolsa@...nel.org> wrote:
>
> Currently we allow pipe input/output only through '-' string
> being passed to '-o' or '-i' options, like:
>
> # mkfifo perf.pipe
> # perf record --no-buffering -e 'sched:sched_switch' -o - > perf.pipe &
> [1] 354406
> # cat perf.pipe | ./perf --no-pager script -i - | head -3
> perf 354406 [000] 168190.164921: sched:sched_switch: perf:354406..
> migration/0 12 [000] 168190.164928: sched:sched_switch: migration/0:..
> perf 354406 [001] 168190.164981: sched:sched_switch: perf:354406..
> ...
>
> This patch detects if given path is pipe and set the perf data
> object accordingly, so it's possible now to do above with:
>
> # mkfifo perf.pipe
> # perf record --no-buffering -e 'sched:sched_switch' -o perf.pipe &
> [1] 360188
> # perf --no-pager script -i ./perf.pipe | head -3
> perf 354442 [000] 168275.464895: sched:sched_switch: perf:354442..
> migration/0 12 [000] 168275.464902: sched:sched_switch: migration/0:..
> perf 354442 [001] 168275.464953: sched:sched_switch: perf:354442..
>
> It's of course possible to combine any of above ways.
>
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
> tools/perf/util/data.c | 27 +++++++++++++++++++++------
> 1 file changed, 21 insertions(+), 6 deletions(-)
>
> diff --git a/tools/perf/util/data.c b/tools/perf/util/data.c
> index f29af4fc3d09..767b6c903cf5 100644
> --- a/tools/perf/util/data.c
> +++ b/tools/perf/util/data.c
> @@ -159,7 +159,7 @@ int perf_data__update_dir(struct perf_data *data)
> return 0;
> }
>
> -static bool check_pipe(struct perf_data *data)
> +static int check_pipe(struct perf_data *data)
> {
> struct stat st;
> bool is_pipe = false;
> @@ -172,6 +172,15 @@ static bool check_pipe(struct perf_data *data)
> } else {
> if (!strcmp(data->path, "-"))
> is_pipe = true;
> + else if (!stat(data->path, &st) && S_ISFIFO(st.st_mode)) {
> + int flags = perf_data__is_read(data) ?
> + O_RDONLY : O_WRONLY|O_CREAT|O_TRUNC;
I don't think we need O_CREAT here (maybe O_TRUNC as well).
Thanks,
Namhyung
> +
> + fd = open(data->path, flags);
> + if (fd < 0)
> + return -EINVAL;
> + is_pipe = true;
> + }
> }
>
> if (is_pipe) {
> @@ -190,7 +199,8 @@ static bool check_pipe(struct perf_data *data)
> }
> }
>
> - return data->is_pipe = is_pipe;
> + data->is_pipe = is_pipe;
> + return 0;
> }
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