Em Fri, Oct 23, 2015 at 10:43:49AM +0000, Wang Nan escreveu:
> Inherit bit is useless for a system wide evsel [1]. Further kernel
> improvements are giving more constrain [2] on inherit events. This
> patch set inherit bit to 0 to avoid potential constrains.
>
> [1]
> http://lkml.kernel.org/r/[email protected]
> [2] http://lkml.kernel.org/r/[email protected]
>
> Signed-off-by: Wang Nan <[email protected]>
> Cc: Arnaldo Carvalho de Melo <[email protected]>
> Cc: Alexei Starovoitov <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Cc: Li Zefan <[email protected]>
> Cc: [email protected]
> Link: http://lkml.kernel.org/n/[email protected]
> ---
>
> evsel->system_wide doesn't correct reflect whether this evsel is system
> wide or not, so checks pid when invoking perf_event_open, and it is
> always correct.
Can't we do this at perf_evlist__config() or perf_evsel__config() time?
We have record_opts at perf_evsel__config() time and I think we should
leave changing the attr at perf_evsel__open() time for feature
fallbacks, i.e. something we will only know when trying to use, which is
different from this inherit-on-syswide case, that we know far in advance
we will not need.
- Arnaldo
> ---
> tools/perf/util/evsel.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 5566b16..e2d6c9a 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -1337,6 +1337,7 @@ retry_sample_id:
>
> for (thread = 0; thread < nthreads; thread++) {
> int group_fd;
> + struct perf_event_attr attr;
>
> if (!evsel->cgrp && !evsel->system_wide)
> pid = thread_map__pid(threads, thread);
> @@ -1346,7 +1347,10 @@ retry_open:
> pr_debug2("sys_perf_event_open: pid %d cpu %d
> group_fd %d flags %#lx\n",
> pid, cpus->map[cpu], group_fd, flags);
>
> - FD(evsel, cpu, thread) =
> sys_perf_event_open(&evsel->attr,
> + attr = evsel->attr;
> + if (pid == -1)
> + attr.inherit = 0;
> + FD(evsel, cpu, thread) = sys_perf_event_open(&attr,
> pid,
>
> cpus->map[cpu],
> group_fd,
> flags);
> --
> 1.8.3.4
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