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Subject[PATCH 2/2] perf tools: Add option to show time history of event samples
Date
Add a timehist option to perf record to save cpu and kernel timestamp
with each sample. Add timehist option to perf report to display the
cpu and timestamps for each event sample rather than generating a
histogram. The timehist option leverages the reference timestamp
from the perf header to create time-of-day stamps.

This option has been extremely in analyzing context switches. The
time history output can be mined for data such as how long a process
runs when scheduled in, where it is when scheduled out (ie., backtrace)
and how long between schedule in events.

Signed-off-by: David Ahern <daahern@cisco.com>
---
tools/perf/builtin-record.c | 8 +++
tools/perf/builtin-report.c | 120 ++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 126 insertions(+), 2 deletions(-)
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 024e144..2496b04 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -49,6 +49,7 @@ static int group = 0;
static int realtime_prio = 0;
static bool raw_samples = false;
static bool system_wide = false;
+static bool time_history = false;
static pid_t target_pid = -1;
static pid_t target_tid = -1;
static pid_t *all_tids = NULL;
@@ -281,6 +282,11 @@ static void create_counter(int counter, int cpu)
if (system_wide)
attr->sample_type |= PERF_SAMPLE_CPU;

+ if (time_history) {
+ attr->sample_type |= PERF_SAMPLE_TIME;
+ attr->sample_type |= PERF_SAMPLE_CPU;
+ }
+
if (raw_samples) {
attr->sample_type |= PERF_SAMPLE_TIME;
attr->sample_type |= PERF_SAMPLE_RAW;
@@ -840,6 +846,8 @@ const struct option record_options[] = {
"do not update the buildid cache"),
OPT_BOOLEAN('B', "no-buildid", &no_buildid,
"do not collect buildids in perf.data"),
+ OPT_BOOLEAN(0, "timehist", &time_history,
+ "collect data for time history report"),
OPT_END()
};

diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index 5de405d..042dc7c 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -35,6 +35,7 @@ static char const *input_name = "perf.data";
static bool force, use_tui, use_stdio;
static bool hide_unresolved;
static bool dont_use_callchains;
+static bool time_history;

static bool show_threads;
static struct perf_read_values show_threads_values;
@@ -124,6 +125,106 @@ out_free_syms:
return err;
}

+static const char *timestr(u64 timestamp, struct perf_session *session)
+{
+ struct tm ltime;
+ u64 dt;
+ struct timeval tv_dt, tv_res;
+ static char tstr[64];
+
+ dt = timestamp - session->header.nsec_ref;
+ tv_dt.tv_sec = (time_t) (dt / NSEC_PER_SEC);
+ tv_dt.tv_usec = (suseconds_t) ((dt - tv_dt.tv_sec * NSEC_PER_SEC) / 1000);
+
+ timeradd(&session->header.tv_ref, &tv_dt, &tv_res);
+
+ if ((session->header.nsec_ref == 0) ||
+ (localtime_r(&tv_res.tv_sec, &ltime) == NULL)) {
+ snprintf(tstr, sizeof(tstr), "00:00:00.000000 %16Ld", timestamp);
+ } else {
+ char date[64];
+ strftime(date, sizeof(date), "%H:%M:%S", &ltime);
+ snprintf(tstr, sizeof(tstr), "%s.%06ld %16Ld",
+ date, tv_res.tv_usec, timestamp);
+ }
+
+ return tstr;
+}
+
+#define TIMEHIST_FMT "%33s %3d %-16s %5d %16Lx %s (%s)\n"
+
+static void timehist_header(void)
+{
+ printf("%33s %3s %-16s %5s %16s %s (%s)\n",
+ " Time-of-Day Kernel Timestamp",
+ "cpu", "Command Name", "PID",
+ " IP ", "Symbol Name", "DSO Name");
+}
+
+static int perf_session__print_sample(struct perf_session *self,
+ struct addr_location *al,
+ struct sample_data *data)
+{
+ static int show_timehist_error = 1;
+ u64 timestamp = 0;
+ struct map_symbol *syms = NULL;
+ struct symbol *parent = NULL;
+ const char *tstr;
+
+ if (show_timehist_error &&
+ ((data->cpu == (u32) -1) || !(self->sample_type & PERF_SAMPLE_TIME))) {
+ pr_err("Data for time history missing in perf event samples.\n"
+ "Did you record with -T option?\n");
+ show_timehist_error = 0;
+ }
+
+ if (self->sample_type & PERF_SAMPLE_TIME)
+ timestamp = data->time;
+
+ tstr = timestr(timestamp, self);
+
+
+ if ((symbol_conf.use_callchain) && data->callchain) {
+ u64 i;
+
+ syms = perf_session__resolve_callchain(self, al->thread,
+ data->callchain, &parent);
+ if (syms == NULL)
+ return -ENOMEM;
+
+ for (i = 0; i < data->callchain->nr; ++i) {
+ const char *symname = "", *dsoname = "";
+
+ if (syms[i].sym && syms[i].sym->name)
+ symname = syms[i].sym->name;
+ else if (hide_unresolved)
+ continue;
+
+ if (syms[i].map && syms[i].map->dso &&
+ syms[i].map->dso->name)
+ dsoname = syms[i].map->dso->name;
+ else if (hide_unresolved)
+ continue;
+
+ printf(TIMEHIST_FMT,
+ tstr, data->cpu,
+ al->thread->comm, al->thread->pid,
+ data->callchain->ips[i], symname, dsoname);
+ }
+
+ free(syms);
+
+ } else {
+ printf(TIMEHIST_FMT,
+ tstr, data->cpu,
+ al->thread->comm, al->thread->pid, al->addr,
+ al->sym->name, al->map->dso->name);
+ }
+ printf("\n");
+
+ return 0;
+}
+
static int add_event_total(struct perf_session *session,
struct sample_data *data,
struct perf_event_attr *attr)
@@ -165,7 +266,9 @@ static int process_sample_event(event_t *event, struct perf_session *session)
if (al.filtered || (hide_unresolved && al.sym == NULL))
return 0;

- if (perf_session__add_hist_entry(session, &al, &data)) {
+ if (time_history) {
+ perf_session__print_sample(session, &al, &data);
+ } else if (perf_session__add_hist_entry(session, &al, &data)) {
pr_debug("problem incrementing symbol period, skipping event\n");
return -1;
}
@@ -318,6 +421,14 @@ static int __cmd_report(void)
if (ret)
goto out_delete;

+ if (time_history) {
+ if (!session->header.nsec_ref) {
+ pr_err("Reference timestamp missing in perf.data file.\n"
+ "Cannot convert kernel timestamps to time-of-day.\n");
+ }
+ timehist_header();
+ }
+
ret = perf_session__process_events(session, &event_ops);
if (ret)
goto out_delete;
@@ -333,6 +444,9 @@ static int __cmd_report(void)
if (verbose > 2)
perf_session__fprintf_dsos(session, stdout);

+ if (time_history)
+ goto out_delete;
+
next = rb_first(&session->hists_tree);
while (next) {
struct hists *hists;
@@ -478,6 +592,8 @@ static const struct option options[] = {
"columns '.' is reserved."),
OPT_BOOLEAN('U', "hide-unresolved", &hide_unresolved,
"Only display entries resolved to a symbol"),
+ OPT_BOOLEAN(0, "timehist", &time_history,
+ "Dump time history of event samples"),
OPT_END()
};

@@ -485,7 +601,7 @@ int cmd_report(int argc, const char **argv, const char *prefix __used)
{
argc = parse_options(argc, argv, options, report_usage, 0);

- if (use_stdio)
+ if (use_stdio || time_history)
use_browser = 0;
else if (use_tui)
use_browser = 1;
--
1.7.2.3


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