Messages in this thread | | | Date | Fri, 31 Jul 2020 18:15:19 +0200 | From | Jiri Olsa <> | Subject | Re: [PATCH 2/6] perf tools: Store clock references for -k/--clockid option |
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On Fri, Jul 31, 2020 at 06:52:36PM +0300, Alexey Budankov wrote: > > On 31.07.2020 0:39, Jiri Olsa wrote: > > Adding new CLOCK_DATA feature that stores reference times > > when -k/--clockid option is specified. > > > > It contains clock id and its reference time together with > > wall clock time taken at the 'same time', both values are > > in nanoseconds. > > > > The format of data is as below: > > > > struct { > > u32 version; /* version = 1 */ > > u32 clockid; > > u64 clockid_time_ns; > > u64 wall_clock_ns; > > }; > > > > This clock reference times will be used in following changes > > to display wall clock for perf events. > > > > It's available only for recording with clockid specified, > > because it's the only case where we can get reference time > > to wallclock time. It's can't do that with perf clock yet. > > > > Original-patch-by: David Ahern <dsahern@gmail.com> > > Signed-off-by: Jiri Olsa <jolsa@kernel.org> > > --- > > .../Documentation/perf.data-file-format.txt | 13 ++ > > tools/perf/builtin-record.c | 41 +++++++ > > tools/perf/util/env.h | 12 ++ > > tools/perf/util/header.c | 112 ++++++++++++++++++ > > tools/perf/util/header.h | 1 + > > 5 files changed, 179 insertions(+) > > > > diff --git a/tools/perf/Documentation/perf.data-file-format.txt b/tools/perf/Documentation/perf.data-file-format.txt > > index b6472e463284..c484e81987c7 100644 > > --- a/tools/perf/Documentation/perf.data-file-format.txt > > +++ b/tools/perf/Documentation/perf.data-file-format.txt > > @@ -389,6 +389,19 @@ struct { > > Example: > > cpu pmu capabilities: branches=32, max_precise=3, pmu_name=icelake > > > > + HEADER_CLOCK_DATA = 29, > > + > > + Contains clock id and its reference time together with wall clock > > + time taken at the 'same time', both values are in nanoseconds. > > + The format of data is as below. > > + > > +struct { > > + u32 version; /* version = 1 */ > > + u32 clockid; > > + u64 clockid_time_ns; > > + u64 wall_clock_ns; > > +}; > > + > > other bits are reserved and should ignored for now > > HEADER_FEAT_BITS = 256, > > > > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c > > index 468c669519a6..f8280e721e1a 100644 > > --- a/tools/perf/builtin-record.c > > +++ b/tools/perf/builtin-record.c > > @@ -70,6 +70,7 @@ > > #include <linux/time64.h> > > #include <linux/zalloc.h> > > #include <linux/bitmap.h> > > +#include <sys/time.h> > > > > struct switch_output { > > bool enabled; > > @@ -1203,6 +1204,9 @@ static void record__init_features(struct record *rec) > > if (!(rec->opts.use_clockid && rec->opts.clockid_res_ns)) > > perf_header__clear_feat(&session->header, HEADER_CLOCKID); > > > > + if (!rec->opts.use_clockid) > > + perf_header__clear_feat(&session->header, HEADER_CLOCK_DATA); > > + > > perf_header__clear_feat(&session->header, HEADER_DIR_FORMAT); > > if (!record__comp_enabled(rec)) > > perf_header__clear_feat(&session->header, HEADER_COMPRESSED); > > @@ -1551,6 +1555,40 @@ static int record__setup_sb_evlist(struct record *rec) > > return 0; > > } > > > > +static int record__init_clock(struct record *rec) > > +{ > > + struct perf_session *session = rec->session; > > + struct timespec ref_clockid; > > + struct timeval ref_tod; > > + u64 ref; > > + > > + if (!rec->opts.use_clockid) > > + return 0; > > + > > + session->header.env.clock.clockid = rec->opts.clockid; > > + > > + if (gettimeofday(&ref_tod, NULL) != 0) { > > + pr_err("gettimeofday failed, cannot set reference time.\n"); > > + return -1; > > + } > > + > > + if (clock_gettime(rec->opts.clockid, &ref_clockid)) { > > + pr_err("clock_gettime failed, cannot set reference time.\n"); > > + return -1; > > + } > > It might also want to be implemented in a loop and iteration with minimal > time delta is chosen to improve synchronization accuracy and also mitigate > possible context switches between gettimeofday() and clock_gettime() calls.
right, we could make this more accurate.. I'll post some follow up change with that
thanks, jirka
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