perf record: Add an option to take an AUX snapshot on exit

It is sometimes useful to generate a snapshot when perf record exits;
I've been using a wrapper script around the workload that would do a
killall -USR2 perf when the workload exits.

This patch makes it easier and also works when perf record is attached
to a pre-existing task. A new snapshot option 'e' can be specified in
-S to enable this behavior:

root@elsewhere:~# perf record -e intel_pt// -Se sleep 1
[ perf record: Woken up 2 times to write data ]
[ perf record: Captured and wrote 0.085 MB perf.data ]

Co-developed-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20190806144101.62892-1-alexander.shishkin@linux.intel.com
[ Fixed up !HAVE_AUXTRACE_SUPPORT build in builtin-record.c, adding 2 missing __maybe_unused ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 15e0fa8..d5e58e0 100644 (file)
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -422,9 +422,14 @@ CLOCK_BOOTTIME, CLOCK_REALTIME and CLOCK_TAI.
 -S::
 --snapshot::
 Select AUX area tracing Snapshot Mode. This option is valid only with an
-AUX area tracing event. Optionally the number of bytes to capture per
-snapshot can be specified. In Snapshot Mode, trace data is captured only when
-signal SIGUSR2 is received.
+AUX area tracing event. Optionally, certain snapshot capturing parameters
+can be specified in a string that follows this option:
+  'e': take one last snapshot on exit; guarantees that there is at least one
+       snapshot in the output file;
+  <size>: if the PMU supports this, specify the desired snapshot size.
+
+In Snapshot Mode trace data is captured only when signal SIGUSR2 is received
+and on exit if the above 'e' option is given.
 
 --proc-map-timeout::
 When processing pre-existing threads /proc/XXX/mmap, it may take a long time,

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index d31d7a5..f71631f 100644 (file)
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -613,19 +613,35 @@ out:
        return rc;
 }
 
-static void record__read_auxtrace_snapshot(struct record *rec)
+static void record__read_auxtrace_snapshot(struct record *rec, bool on_exit)
 {
        pr_debug("Recording AUX area tracing snapshot\n");
        if (record__auxtrace_read_snapshot_all(rec) < 0) {
                trigger_error(&auxtrace_snapshot_trigger);
        } else {
-               if (auxtrace_record__snapshot_finish(rec->itr))
+               if (auxtrace_record__snapshot_finish(rec->itr, on_exit))
                        trigger_error(&auxtrace_snapshot_trigger);
                else
                        trigger_ready(&auxtrace_snapshot_trigger);
        }
 }
 
+static int record__auxtrace_snapshot_exit(struct record *rec)
+{
+       if (trigger_is_error(&auxtrace_snapshot_trigger))
+               return 0;
+
+       if (!auxtrace_record__snapshot_started &&
+           auxtrace_record__snapshot_start(rec->itr))
+               return -1;
+
+       record__read_auxtrace_snapshot(rec, true);
+       if (trigger_is_error(&auxtrace_snapshot_trigger))
+               return -1;
+
+       return 0;
+}
+
 static int record__auxtrace_init(struct record *rec)
 {
        int err;
@@ -654,7 +670,8 @@ int record__auxtrace_mmap_read(struct record *rec __maybe_unused,
 }
 
 static inline
-void record__read_auxtrace_snapshot(struct record *rec __maybe_unused)
+void record__read_auxtrace_snapshot(struct record *rec __maybe_unused,
+                                   bool on_exit __maybe_unused)
 {
 }
 
@@ -664,6 +681,12 @@ int auxtrace_record__snapshot_start(struct auxtrace_record *itr __maybe_unused)
        return 0;
 }
 
+static inline
+int record__auxtrace_snapshot_exit(struct record *rec __maybe_unused)
+{
+       return 0;
+}
+
 static int record__auxtrace_init(struct record *rec __maybe_unused)
 {
        return 0;
@@ -1536,7 +1559,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
                if (auxtrace_record__snapshot_started) {
                        auxtrace_record__snapshot_started = 0;
                        if (!trigger_is_error(&auxtrace_snapshot_trigger))
-                               record__read_auxtrace_snapshot(rec);
+                               record__read_auxtrace_snapshot(rec, false);
                        if (trigger_is_error(&auxtrace_snapshot_trigger)) {
                                pr_err("AUX area tracing snapshot failed\n");
                                err = -1;
@@ -1609,9 +1632,13 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
                        disabled = true;
                }
        }
+
        trigger_off(&auxtrace_snapshot_trigger);
        trigger_off(&switch_output_trigger);
 
+       if (opts->auxtrace_snapshot_on_exit)
+               record__auxtrace_snapshot_exit(rec);
+
        if (forks && workload_exec_errno) {
                char msg[STRERR_BUFSIZE];
                const char *emsg = str_error_r(workload_exec_errno, msg, sizeof(msg));

diff --git a/tools/perf/perf.h b/tools/perf/perf.h
index 74d0124..dc0a7a2 100644 (file)
--- a/tools/perf/perf.h
+++ b/tools/perf/perf.h
@@ -57,6 +57,7 @@ struct record_opts {
        bool         running_time;
        bool         full_auxtrace;
        bool         auxtrace_snapshot_mode;
+       bool         auxtrace_snapshot_on_exit;
        bool         record_namespaces;
        bool         record_switch_events;
        bool         all_kernel;

diff --git a/tools/perf/util/auxtrace.c b/tools/perf/util/auxtrace.c
index 65728cd..72ce4c5 100644 (file)
--- a/tools/perf/util/auxtrace.c
+++ b/tools/perf/util/auxtrace.c
@@ -539,9 +539,9 @@ int auxtrace_record__snapshot_start(struct auxtrace_record *itr)
        return 0;
 }
 
-int auxtrace_record__snapshot_finish(struct auxtrace_record *itr)
+int auxtrace_record__snapshot_finish(struct auxtrace_record *itr, bool on_exit)
 {
-       if (itr && itr->snapshot_finish)
+       if (!on_exit && itr && itr->snapshot_finish)
                return itr->snapshot_finish(itr);
        return 0;
 }
@@ -577,6 +577,16 @@ int auxtrace_parse_snapshot_options(struct auxtrace_record *itr,
        if (!str)
                return 0;
 
+       /* PMU-agnostic options */
+       switch (*str) {
+       case 'e':
+               opts->auxtrace_snapshot_on_exit = true;
+               str++;
+               break;
+       default:
+               break;
+       }
+
        if (itr)
                return itr->parse_snapshot_options(itr, opts, str);
 

diff --git a/tools/perf/util/auxtrace.h b/tools/perf/util/auxtrace.h
index 17eb04a..8ccabac 100644 (file)
--- a/tools/perf/util/auxtrace.h
+++ b/tools/perf/util/auxtrace.h
@@ -499,7 +499,7 @@ int auxtrace_record__info_fill(struct auxtrace_record *itr,
                               size_t priv_size);
 void auxtrace_record__free(struct auxtrace_record *itr);
 int auxtrace_record__snapshot_start(struct auxtrace_record *itr);
-int auxtrace_record__snapshot_finish(struct auxtrace_record *itr);
+int auxtrace_record__snapshot_finish(struct auxtrace_record *itr, bool on_exit);
 int auxtrace_record__find_snapshot(struct auxtrace_record *itr, int idx,
                                   struct auxtrace_mmap *mm,
                                   unsigned char *data, u64 *head, u64 *old);