Messages in this thread | | | From | Ian Rogers <> | Date | Mon, 4 May 2020 16:27:31 -0700 | Subject | Re: [PATCH] perf session: Try to read pipe data from file |
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On Mon, May 4, 2020 at 3:57 PM Jiri Olsa <jolsa@redhat.com> wrote: > > On Fri, May 01, 2020 at 01:34:47PM +0200, Jiri Olsa wrote: > > From: Jiri Olsa <jolsa@redhat.com> > > > > Ian came with the idea of having support to read the pipe > > data also from file [1]. Currently pipe mode files fails > > like: > > > > $ perf record -o - sleep 1 > /tmp/perf.pipe.data > > $ perf report -i /tmp/perf.pipe.data > > incompatible file format (rerun with -v to learn more) > > > > This patch adds the support to do that by trying the pipe > > header first, and if its successfully detected, switching > > the perf data to pipe mode. > > > > [1] https://lore.kernel.org/lkml/20200409185744.255881-1-irogers@google.com/ > > Original-patch-by: Ian Rogers <irogers@google.com> > > Signed-off-by: Jiri Olsa <jolsa@kernel.org> > > actualy.. I found another issue while trying this on tracepoints: > > # ./perf record -g -e 'raw_syscalls:sys_enter' -o - true > data > [ perf record: Woken up 1 times to write data ] > [ perf record: Captured and wrote 0.000 MB - ] > # ./perf script -i ./data > perf_event__process_tracing_data: tracing data size mismatch0x1034 [0xc]: failed to process type: 66 > > it's because some of the pipe synthesize code calls lseek, which > fails on pipe, but succeeds on normal file (with pipe data) > > patch below fixes that for me, but I wonder there are other leftovers > like this.. I'll check on post it all together
Thanks for testing! I wonder in the 2nd case whether a comment as to why the seek isn't needed in pipe mode would be useful.
Ian
> jirka > > > --- > diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c > index 8ca709f938b8..33e299674121 100644 > --- a/tools/perf/util/header.c > +++ b/tools/perf/util/header.c > @@ -3955,13 +3955,8 @@ int perf_event__process_tracing_data(struct perf_session *session, > { > ssize_t size_read, padding, size = event->tracing_data.size; > int fd = perf_data__fd(session->data); > - off_t offset = lseek(fd, 0, SEEK_CUR); > char buf[BUFSIZ]; > > - /* setup for reading amidst mmap */ > - lseek(fd, offset + sizeof(struct perf_record_header_tracing_data), > - SEEK_SET); > - > size_read = trace_report(fd, &session->tevent, > session->repipe); > padding = PERF_ALIGN(size_read, sizeof(u64)) - size_read; > diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c > index c11d89e0ee55..b75df19feaf1 100644 > --- a/tools/perf/util/session.c > +++ b/tools/perf/util/session.c > @@ -1543,7 +1543,8 @@ static s64 perf_session__process_user_event(struct perf_session *session, > return 0; > case PERF_RECORD_HEADER_TRACING_DATA: > /* setup for reading amidst mmap */ > - lseek(fd, file_offset, SEEK_SET); > + if (!perf_data__is_pipe(session->data)) > + lseek(fd, file_offset, SEEK_SET); > return tool->tracing_data(session, event); > case PERF_RECORD_HEADER_BUILD_ID: > return tool->build_id(session, event); >
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