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SubjectRe: [PATCH] perf, record: Add clockid parameter
On 3/27/15 8:32 AM, Peter Zijlstra wrote:
> On Fri, Mar 27, 2015 at 04:48:08AM -0700, tip-bot for Peter Zijlstra wrote:
>> perf: Add per event clockid support
>
> And here the accompanying userspace; which I'd totally forgotten about.
>
> XXX: do we want to store the clockid in the data file as well, such that
> we can verify at perf-inject time the clocks match with our
> expectations?
>
> ---
> Subject: perf, record: Add clockid parameter
>
> Teach perf-record about the new perf_event_attr::{use_clockid, clockid}
> fields. Add a simple parameter to set the clock (if any) to be used for
> the events to be recorded into the data file.
>
> Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
> tools/perf/builtin-record.c | 3 +++
> tools/perf/perf.h | 1 +
> tools/perf/util/evsel.c | 5 +++++
> 3 files changed, 9 insertions(+)

missing Documentation/perf-record.txt update

>
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 18aad239b401..9d4ed884b1c8 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -739,6 +739,7 @@ static struct record record = {
> .uses_mmap = true,
> .default_per_cpu = true,
> },
> + .clockid = -1,
> },
> .tool = {
> .sample = process_sample_event,
> @@ -842,6 +843,8 @@ struct option __record_options[] = {
> "Sample machine registers on interrupt"),
> OPT_BOOLEAN(0, "running-time", &record.opts.running_time,
> "Record running/enabled time of read (:S) events"),
> + OPT_INTEGER('k', "clockid", &record.opts.clockid,
> + "clockid to use for events"),
> OPT_END()
> };
>
> diff --git a/tools/perf/perf.h b/tools/perf/perf.h
> index c38a085a5571..275c0c58fbbe 100644
> --- a/tools/perf/perf.h
> +++ b/tools/perf/perf.h
> @@ -62,6 +62,7 @@ struct record_opts {
> u64 user_interval;
> bool sample_transaction;
> unsigned initial_delay;
> + clockid_t clockid;
> };
>
> struct option;
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 358e5954baa8..309208b16632 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -761,6 +761,11 @@ void perf_evsel__config(struct perf_evsel *evsel, struct record_opts *opts)
> attr->disabled = 0;
> attr->enable_on_exec = 0;
> }
> +
> + if (opts->clockid >= 0) {
> + attr->use_clockid = 1;
> + attr->clockid = opts->clockid;
> + }
> }
>
> static int perf_evsel__alloc_fd(struct perf_evsel *evsel, int ncpus, int nthreads)
>

This is a new feature which means use_clockid on older kernels will
fail. So need to catch that and throw an error -- perhaps yet another
probe function.

Also, if the intent is to allow clock selection per event should there
be an event modifier as well (see get_event_modifier())?



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