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Subject[tip:perf/core] perf tools: handle PERF_RECORD_LOST_SAMPLES
Commit-ID:  c4937a91ea56b546234b0608a413ebad90536d26
Gitweb: http://git.kernel.org/tip/c4937a91ea56b546234b0608a413ebad90536d26
Author: Kan Liang <kan.liang@intel.com>
AuthorDate: Sun, 10 May 2015 15:13:15 -0400
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Sun, 7 Jun 2015 16:09:06 +0200

perf tools: handle PERF_RECORD_LOST_SAMPLES

This patch modifies the perf tool to handle the new RECORD type,
PERF_RECORD_LOST_SAMPLES.

The number of lost-sample events is stored in
.nr_events[PERF_RECORD_LOST_SAMPLES]. The exact number of samples
which the kernel dropped is stored in total_lost_samples.

When the percentage of dropped samples is greater than 5%, a warning
is printed.

Here are some examples:

Eg 1, Recording different frequently-occurring events is safe with the
patch. Only a very low drop rate is associated with such actions.

$ perf record -e '{cycles:p,instructions:p}' -c 20003 --no-time ~/tchain ~/tchain

$ perf report -D | tail
SAMPLE events: 120243
MMAP2 events: 5
LOST_SAMPLES events: 24
FINISHED_ROUND events: 15
cycles:p stats:
TOTAL events: 59348
SAMPLE events: 59348
instructions:p stats:
TOTAL events: 60895
SAMPLE events: 60895

$ perf report --stdio --group
# To display the perf.data header info, please use --header/--header-only options.
#
#
# Total Lost Samples: 24
#
# Samples: 120K of event 'anon group { cycles:p, instructions:p }'
# Event count (approx.): 24048600000
#
# Overhead Command Shared Object Symbol
# ................ ........... ................
..................................
#
99.74% 99.86% tchain_edit tchain_edit [.] f3
0.09% 0.02% tchain_edit tchain_edit [.] f2
0.04% 0.00% tchain_edit [kernel.vmlinux] [k] ixgbe_read_reg

Eg 2, Recording the same thing multiple times can lead to high drop
rate, but it is not a useful configuration.

$ perf record -e '{cycles:p,cycles:p}' -c 20003 --no-time ~/tchain
Warning: Processed 600592 samples and lost 99.73% samples!
[perf record: Woken up 148 times to write data]
[perf record: Captured and wrote 36.922 MB perf.data (1206322 samples)]
[perf record: Woken up 1 times to write data]
[perf record: Captured and wrote 0.121 MB perf.data (1629 samples)]

Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: acme@infradead.org
Cc: eranian@google.com
Link: http://lkml.kernel.org/r/1431285195-14269-9-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
tools/perf/builtin-report.c | 1 +
tools/perf/util/event.c | 9 +++++++++
tools/perf/util/event.h | 17 +++++++++++++++++
tools/perf/util/machine.c | 10 ++++++++++
tools/perf/util/machine.h | 2 ++
tools/perf/util/session.c | 19 +++++++++++++++++++
tools/perf/util/tool.h | 1 +
7 files changed, 59 insertions(+)

diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index 56025d9..628090b 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -320,6 +320,7 @@ static int perf_evlist__tty_browse_hists(struct perf_evlist *evlist,
{
struct perf_evsel *pos;

+ fprintf(stdout, "#\n# Total Lost Samples: %lu\n#\n", evlist->stats.total_lost_samples);
evlist__for_each(evlist, pos) {
struct hists *hists = evsel__hists(pos);
const char *evname = perf_evsel__name(pos);
diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index c192596..793b150 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -25,6 +25,7 @@ static const char *perf_event__names[] = {
[PERF_RECORD_SAMPLE] = "SAMPLE",
[PERF_RECORD_AUX] = "AUX",
[PERF_RECORD_ITRACE_START] = "ITRACE_START",
+ [PERF_RECORD_LOST_SAMPLES] = "LOST_SAMPLES",
[PERF_RECORD_HEADER_ATTR] = "ATTR",
[PERF_RECORD_HEADER_EVENT_TYPE] = "EVENT_TYPE",
[PERF_RECORD_HEADER_TRACING_DATA] = "TRACING_DATA",
@@ -712,6 +713,14 @@ int perf_event__process_itrace_start(struct perf_tool *tool __maybe_unused,
return machine__process_itrace_start_event(machine, event);
}

+int perf_event__process_lost_samples(struct perf_tool *tool __maybe_unused,
+ union perf_event *event,
+ struct perf_sample *sample,
+ struct machine *machine)
+{
+ return machine__process_lost_samples_event(machine, event, sample);
+}
+
size_t perf_event__fprintf_mmap(union perf_event *event, FILE *fp)
{
return fprintf(fp, " %d/%d: [%#" PRIx64 "(%#" PRIx64 ") @ %#" PRIx64 "]: %c %s\n",
diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
index 97179ab..5dc51ad 100644
--- a/tools/perf/util/event.h
+++ b/tools/perf/util/event.h
@@ -52,6 +52,11 @@ struct lost_event {
u64 lost;
};

+struct lost_samples_event {
+ struct perf_event_header header;
+ u64 lost;
+};
+
/*
* PERF_FORMAT_ENABLED | PERF_FORMAT_RUNNING | PERF_FORMAT_ID
*/
@@ -235,6 +240,12 @@ enum auxtrace_error_type {
* total_lost tells exactly how many events the kernel in fact lost, i.e. it is
* the sum of all struct lost_event.lost fields reported.
*
+ * The kernel discards mixed up samples and sends the number in a
+ * PERF_RECORD_LOST_SAMPLES event. The number of lost-samples events is stored
+ * in .nr_events[PERF_RECORD_LOST_SAMPLES] while total_lost_samples tells
+ * exactly how many samples the kernel in fact dropped, i.e. it is the sum of
+ * all struct lost_samples_event.lost fields reported.
+ *
* The total_period is needed because by default auto-freq is used, so
* multipling nr_events[PERF_EVENT_SAMPLE] by a frequency isn't possible to get
* the total number of low level events, it is necessary to to sum all struct
@@ -244,6 +255,7 @@ struct events_stats {
u64 total_period;
u64 total_non_filtered_period;
u64 total_lost;
+ u64 total_lost_samples;
u64 total_invalid_chains;
u32 nr_events[PERF_RECORD_HEADER_MAX];
u32 nr_non_filtered_samples;
@@ -342,6 +354,7 @@ union perf_event {
struct comm_event comm;
struct fork_event fork;
struct lost_event lost;
+ struct lost_samples_event lost_samples;
struct read_event read;
struct throttle_event throttle;
struct sample_event sample;
@@ -390,6 +403,10 @@ int perf_event__process_lost(struct perf_tool *tool,
union perf_event *event,
struct perf_sample *sample,
struct machine *machine);
+int perf_event__process_lost_samples(struct perf_tool *tool,
+ union perf_event *event,
+ struct perf_sample *sample,
+ struct machine *machine);
int perf_event__process_aux(struct perf_tool *tool,
union perf_event *event,
struct perf_sample *sample,
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 9e02c86..f15ed24 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -482,6 +482,14 @@ int machine__process_lost_event(struct machine *machine __maybe_unused,
return 0;
}

+int machine__process_lost_samples_event(struct machine *machine __maybe_unused,
+ union perf_event *event, struct perf_sample *sample)
+{
+ dump_printf(": id:%" PRIu64 ": lost samples :%" PRIu64 "\n",
+ sample->id, event->lost_samples.lost);
+ return 0;
+}
+
static struct dso*
machine__module_dso(struct machine *machine, struct kmod_path *m,
const char *filename)
@@ -1419,6 +1427,8 @@ int machine__process_event(struct machine *machine, union perf_event *event,
ret = machine__process_aux_event(machine, event); break;
case PERF_RECORD_ITRACE_START:
ret = machine__process_itrace_start_event(machine, event);
+ case PERF_RECORD_LOST_SAMPLES:
+ ret = machine__process_lost_samples_event(machine, event, sample); break;
break;
default:
ret = -1;
diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
index 39a0ca0..8e1f796 100644
--- a/tools/perf/util/machine.h
+++ b/tools/perf/util/machine.h
@@ -81,6 +81,8 @@ int machine__process_fork_event(struct machine *machine, union perf_event *event
struct perf_sample *sample);
int machine__process_lost_event(struct machine *machine, union perf_event *event,
struct perf_sample *sample);
+int machine__process_lost_samples_event(struct machine *machine, union perf_event *event,
+ struct perf_sample *sample);
int machine__process_aux_event(struct machine *machine,
union perf_event *event);
int machine__process_itrace_start_event(struct machine *machine,
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 39fe09d..88d87bf 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -325,6 +325,8 @@ void perf_tool__fill_defaults(struct perf_tool *tool)
tool->exit = process_event_stub;
if (tool->lost == NULL)
tool->lost = perf_event__process_lost;
+ if (tool->lost_samples == NULL)
+ tool->lost_samples = perf_event__process_lost_samples;
if (tool->aux == NULL)
tool->aux = perf_event__process_aux;
if (tool->itrace_start == NULL)
@@ -606,6 +608,7 @@ static perf_event__swap_op perf_event__swap_ops[] = {
[PERF_RECORD_SAMPLE] = perf_event__all64_swap,
[PERF_RECORD_AUX] = perf_event__aux_swap,
[PERF_RECORD_ITRACE_START] = perf_event__itrace_start_swap,
+ [PERF_RECORD_LOST_SAMPLES] = perf_event__all64_swap,
[PERF_RECORD_HEADER_ATTR] = perf_event__hdr_attr_swap,
[PERF_RECORD_HEADER_EVENT_TYPE] = perf_event__event_type_swap,
[PERF_RECORD_HEADER_TRACING_DATA] = perf_event__tracing_data_swap,
@@ -1049,6 +1052,10 @@ static int machines__deliver_event(struct machines *machines,
if (tool->lost == perf_event__process_lost)
evlist->stats.total_lost += event->lost.lost;
return tool->lost(tool, event, sample, machine);
+ case PERF_RECORD_LOST_SAMPLES:
+ if (tool->lost_samples == perf_event__process_lost_samples)
+ evlist->stats.total_lost_samples += event->lost_samples.lost;
+ return tool->lost_samples(tool, event, sample, machine);
case PERF_RECORD_READ:
return tool->read(tool, event, sample, evsel, machine);
case PERF_RECORD_THROTTLE:
@@ -1286,6 +1293,18 @@ static void perf_session__warn_about_errors(const struct perf_session *session)
stats->nr_events[PERF_RECORD_LOST]);
}

+ if (session->tool->lost_samples == perf_event__process_lost_samples) {
+ double drop_rate;
+
+ drop_rate = (double)stats->total_lost_samples /
+ (double) (stats->nr_events[PERF_RECORD_SAMPLE] + stats->total_lost_samples);
+ if (drop_rate > 0.05) {
+ ui__warning("Processed %lu samples and lost %3.2f%% samples!\n\n",
+ stats->nr_events[PERF_RECORD_SAMPLE] + stats->total_lost_samples,
+ drop_rate * 100.0);
+ }
+ }
+
if (stats->nr_unknown_events != 0) {
ui__warning("Found %u unknown events!\n\n"
"Is this an older tool processing a perf.data "
diff --git a/tools/perf/util/tool.h b/tools/perf/util/tool.h
index 7f282ad..c307dd4 100644
--- a/tools/perf/util/tool.h
+++ b/tools/perf/util/tool.h
@@ -43,6 +43,7 @@ struct perf_tool {
fork,
exit,
lost,
+ lost_samples,
aux,
itrace_start,
throttle,

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