Messages in this thread | | | From | Namhyung Kim <> | Date | Fri, 30 Oct 2020 14:34:30 +0900 | Subject | Re: [PATCH] perf data: Allow to use stdio functions for pipe mode |
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Hi Jiri,
On Thu, Oct 29, 2020 at 8:57 PM Jiri Olsa <jolsa@redhat.com> wrote: > > On Wed, Oct 28, 2020 at 05:56:32PM +0900, Namhyung Kim wrote: > > When perf data is in a pipe, it reads each event separately using > > read(2) syscall. This is a huge performance bottleneck when > > processing large data like in perf inject. Also perf inject needs to > > use write(2) syscall for the output. > > > > So convert it to use buffer I/O functions in stdio library for pipe > > data. This makes inject-build-id bench time drops from 20ms to 8ms. > > > > $ perf bench internals inject-build-id > > # Running 'internals/inject-build-id' benchmark: > > Average build-id injection took: 8.074 msec (+- 0.013 msec) > > Average time per event: 0.792 usec (+- 0.001 usec) > > Average memory usage: 8328 KB (+- 0 KB) > > Average build-id-all injection took: 5.490 msec (+- 0.008 msec) > > Average time per event: 0.538 usec (+- 0.001 usec) > > Average memory usage: 7563 KB (+- 0 KB) > > > > This patch enables it just for perf inject when used with pipe (it's a > > default behavior). Maybe we could do it for perf record and/or report > > later.. > > > > Signed-off-by: Namhyung Kim <namhyung@kernel.org> > > --- > > tools/perf/builtin-inject.c | 2 ++ > > tools/perf/util/data.c | 36 +++++++++++++++++++++++++++++++++--- > > tools/perf/util/data.h | 11 ++++++++++- > > tools/perf/util/header.c | 8 ++++---- > > tools/perf/util/session.c | 7 ++++--- > > 5 files changed, 53 insertions(+), 11 deletions(-) > > > > diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c > > index 452a75fe68e5..14d6c88fed76 100644 > > --- a/tools/perf/builtin-inject.c > > +++ b/tools/perf/builtin-inject.c > > @@ -853,10 +853,12 @@ int cmd_inject(int argc, const char **argv) > > .output = { > > .path = "-", > > .mode = PERF_DATA_MODE_WRITE, > > + .use_stdio = true, > > }, > > }; > > struct perf_data data = { > > .mode = PERF_DATA_MODE_READ, > > + .use_stdio = true, > > }; > > int ret; > > > > diff --git a/tools/perf/util/data.c b/tools/perf/util/data.c > > index c47aa34fdc0a..47b5a4b50ca5 100644 > > --- a/tools/perf/util/data.c > > +++ b/tools/perf/util/data.c > > @@ -174,8 +174,16 @@ static bool check_pipe(struct perf_data *data) > > is_pipe = true; > > } > > > > - if (is_pipe) > > - data->file.fd = fd; > > + if (is_pipe) { > > + if (data->use_stdio) { > > + const char *mode; > > + > > + mode = perf_data__is_read(data) ? "r" : "w"; > > + data->file.fptr = fdopen(fd, mode); > > I guess fdopen should never fail right? but I think we should > add BUG_ON(data->file.fptr == NULL) or something
The man page says it may fail when mode is invalid or malloc failed internally. Will add the check.
> > other than this the change looks good, I can see the speedup > in bench as well
Thanks! Namhyung
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