Messages in this thread | | | Subject | Re: [PATCH 2/6] perf tools: Store clock references for -k/--clockid option | From | Alexey Budankov <> | Date | Fri, 31 Jul 2020 18:52:36 +0300 |
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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.
Alexei
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