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Date: Tue, 9 Oct 2018 10:41:31 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
Andi Kleen <ak@...ux.intel.com>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] perf record: encode -k clockid frequency into Perf
trace
Em Tue, Oct 09, 2018 at 09:59:03AM +0300, Alexey Budankov escreveu:
>
> Store -k clockid frequency into Perf trace to enable timestamps
> derived metrics conversion into wall clock time on reporting stage.
>
> Below is the example of perf report output:
Some questions below, left the code for easier reference.
> tools/perf/perf record -k raw -- ../../matrix/linux/matrix.gcc
> ...
> [ perf record: Captured and wrote 31.222 MB perf.data (818054 samples) ]
>
> tools/perf/perf report --header
> # ========
> ...
> # event : name = cycles:ppp, , size = 112, { sample_period, sample_freq } = 4000, sample_type = IP|TID|TIME|PERIOD, disabled = 1, inherit = 1, mmap = 1, comm = 1, freq = 1, enable_on_exec = 1, task = 1, precise_ip = 3, sample_id_all = 1, exclude_guest = 1, mmap2 = 1, comm_exec = 1, use_clockid = 1, clockid = 4
> ...
> # clockid frequency: 1000 MHz
> ...
> # ========
>
> Signed-off-by: Alexey Budankov <alexey.budankov@...ux.intel.com>
> ---
> Changes in v4:
> - addressed compilation issues on 32bit platforms
> Changes in v3:
> - moved header's clockid_res_ns initialization out of record__init_features()
> - added explicit warning for case of failed clock_getres() call
> Changes in v2:
> - renamed clockid_freq to clockid_res_ns and get_clockid_freq() to get_clockid_res()
> - avoided redundant define of NSEC_IN_SEC, reused linux/time64.h:NSEC_PER_SEC
> - moved MHz conversion into print_clockid() and shortened write_clockid()
> ---
> tools/perf/builtin-record.c | 24 ++++++++++++++++++++++--
> tools/perf/perf.h | 1 +
> tools/perf/util/env.h | 1 +
> tools/perf/util/header.c | 28 ++++++++++++++++++++++++++++
> tools/perf/util/header.h | 1 +
> 5 files changed, 53 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 0980dfe3396b..d803d3264465 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -592,6 +592,9 @@ static void record__init_features(struct record *rec)
> if (!rec->opts.full_auxtrace)
> perf_header__clear_feat(&session->header, HEADER_AUXTRACE);
>
> + if (!(rec->opts.use_clockid && rec->opts.clockid_res_ns))
> + perf_header__clear_feat(&session->header, HEADER_CLOCKID);
> +
> perf_header__clear_feat(&session->header, HEADER_STAT);
> }
>
> @@ -897,6 +900,9 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
>
> record__init_features(rec);
>
> + if (rec->opts.use_clockid && rec->opts.clockid_res_ns)
> + session->header.env.clockid_res_ns = rec->opts.clockid_res_ns;
> +
> if (forks) {
> err = perf_evlist__prepare_workload(rec->evlist, &opts->target,
> argv, data->is_pipe,
> @@ -1337,6 +1343,19 @@ static const struct clockid_map clockids[] = {
> CLOCKID_END,
> };
>
> +static int get_clockid_res(clockid_t clk_id, size_t *res_ns)
> +{
> + struct timespec res;
> +
> + *res_ns = 0;
> + if (!clock_getres(clk_id, &res))
> + *res_ns = res.tv_nsec + res.tv_sec * NSEC_PER_SEC;
> + else
> + pr_warning("WARNING: Failed to determine specified clock resolution.\n");
> +
> + return 0;
> +}
> +
> static int parse_clockid(const struct option *opt, const char *str, int unset)
> {
> struct record_opts *opts = (struct record_opts *)opt->value;
> @@ -1360,7 +1379,7 @@ static int parse_clockid(const struct option *opt, const char *str, int unset)
>
> /* if its a number, we're done */
> if (sscanf(str, "%d", &opts->clockid) == 1)
> - return 0;
> + return get_clockid_res(opts->clockid, &opts->clockid_res_ns);
>
> /* allow a "CLOCK_" prefix to the name */
> if (!strncasecmp(str, "CLOCK_", 6))
> @@ -1369,7 +1388,8 @@ static int parse_clockid(const struct option *opt, const char *str, int unset)
> for (cm = clockids; cm->name; cm++) {
> if (!strcasecmp(str, cm->name)) {
> opts->clockid = cm->clockid;
> - return 0;
> + return get_clockid_res(opts->clockid,
> + &opts->clockid_res_ns);
> }
> }
>
> diff --git a/tools/perf/perf.h b/tools/perf/perf.h
> index 21bf7f5a3cf5..981db3c2ed60 100644
> --- a/tools/perf/perf.h
> +++ b/tools/perf/perf.h
> @@ -81,6 +81,7 @@ struct record_opts {
> unsigned initial_delay;
> bool use_clockid;
> clockid_t clockid;
> + size_t clockid_res_ns;
> unsigned int proc_map_timeout;
> };
>
> diff --git a/tools/perf/util/env.h b/tools/perf/util/env.h
> index 1f3ccc368530..b167a54d635f 100644
> --- a/tools/perf/util/env.h
> +++ b/tools/perf/util/env.h
> @@ -63,6 +63,7 @@ struct perf_env {
> struct numa_node *numa_nodes;
> struct memory_node *memory_nodes;
> unsigned long long memory_bsize;
> + size_t clockid_res_ns;
> };
>
> extern struct perf_env perf_env;
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index 1ec1d9bc2d63..702e0cce63da 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -1034,6 +1034,14 @@ static int write_auxtrace(struct feat_fd *ff,
> return err;
> }
>
> +static int write_clockid(struct feat_fd *ff,
> + struct perf_evlist *evlist __maybe_unused)
> +{
> + u64 clockid_res_ns = ff->ph->env.clockid_res_ns;
> +
> + return do_write(ff, &clockid_res_ns, sizeof(clockid_res_ns));
> +}
> +
> static int cpu_cache_level__sort(const void *a, const void *b)
> {
> struct cpu_cache_level *cache_a = (struct cpu_cache_level *)a;
> @@ -1508,6 +1516,12 @@ static void print_cpu_topology(struct feat_fd *ff, FILE *fp)
> fprintf(fp, "# Core ID and Socket ID information is not available\n");
> }
>
> +static void print_clockid(struct feat_fd *ff, FILE *fp)
> +{
> + fprintf(fp, "# clockid frequency: %zd MHz\n",
> + ff->ph->env.clockid_res_ns * 1000);
> +}
> +
> static void free_event_desc(struct perf_evsel *events)
> {
> struct perf_evsel *evsel;
> @@ -2531,6 +2545,19 @@ static int process_mem_topology(struct feat_fd *ff,
> return ret;
> }
>
> +static int process_clockid(struct feat_fd *ff,
> + void *data __maybe_unused)
> +{
> + u64 clockid_res_ns;
> +
> + if (do_read_u64(ff, &clockid_res_ns))
> + return -1;
> +
> + ff->ph->env.clockid_res_ns = *(size_t *)&clockid_res_ns;
What is wrong with:
ff->ph->env.clockid_res_ns = clockid_res_ns;
?
Also why have you picked 'size_t' for that nanoseconds variable
(clockid_res_ns)?
When one looks at things like:
struct timespec {
time_t tv_sec; /* seconds */
long tv_nsec; /* nanoseconds */
};
that would lead one to use 'long' for a variable holding nanoseconds,
no?
And 'timespec' is what clock_getres() uses:
int clock_getres(clockid_t clk_id, struct timespec *res);
Since you're storing this as:
+static int get_clockid_res(clockid_t clk_id, size_t *res_ns)
+{
+ struct timespec res;
+
+ *res_ns = 0;
+ if (!clock_getres(clk_id, &res))
+ *res_ns = res.tv_nsec + res.tv_sec * NSEC_PER_SEC;
Why don't you make ff->ph->env.clockid_res_ns an 'u64'? Would simplify
the code a bit, no?
Am I missing something?
- Arnaldo
> + return 0;
> +}
> +
> struct feature_ops {
> int (*write)(struct feat_fd *ff, struct perf_evlist *evlist);
> void (*print)(struct feat_fd *ff, FILE *fp);
> @@ -2590,6 +2617,7 @@ static const struct feature_ops feat_ops[HEADER_LAST_FEATURE] = {
> FEAT_OPN(CACHE, cache, true),
> FEAT_OPR(SAMPLE_TIME, sample_time, false),
> FEAT_OPR(MEM_TOPOLOGY, mem_topology, true),
> + FEAT_OPR(CLOCKID, clockid, false)
> };
>
> struct header_print_data {
> diff --git a/tools/perf/util/header.h b/tools/perf/util/header.h
> index e17903caa71d..0d553ddca0a3 100644
> --- a/tools/perf/util/header.h
> +++ b/tools/perf/util/header.h
> @@ -38,6 +38,7 @@ enum {
> HEADER_CACHE,
> HEADER_SAMPLE_TIME,
> HEADER_MEM_TOPOLOGY,
> + HEADER_CLOCKID,
> HEADER_LAST_FEATURE,
> HEADER_FEAT_BITS = 256,
> };
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