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Subject[PATCH 5/6] perf record: Add switch-output size warning
Date
Adding switch-output size warning if the requested
size of lower than the wakeup ring buffer size.

$ perf record --switch-output=1K ls
WARNING: switch-output data size lower than wakeup kernel buffer size (258K) expect bigger perf.data sizes
...

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-0gafw11lesghnbfoiw90kc3q@git.kernel.org
---
tools/perf/builtin-record.c | 21 +++++++++++++++++++++
tools/perf/util/evlist.c | 2 +-
tools/perf/util/evlist.h | 2 ++
3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 3fa64492ee62..4a70e964cd96 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1377,6 +1377,23 @@ static int record__parse_mmap_pages(const struct option *opt,
return ret;
}

+static void switch_output_size_warn(struct record *rec)
+{
+ u64 wakeup_size = perf_evlist__mmap_size(rec->opts.mmap_pages);
+ struct switch_output *s = &rec->switch_output;
+
+ wakeup_size /= 2;
+
+ if (s->size < wakeup_size) {
+ char buf[100];
+
+ unit_number__scnprint(buf, sizeof(buf), wakeup_size);
+ pr_warning("WARNING: switch-output data size lower than "
+ "wakeup kernel buffer size (%s) "
+ "expect bigger perf.data sizes\n", buf);
+ }
+}
+
static int switch_output_setup(struct record *rec)
{
struct switch_output *s = &rec->switch_output;
@@ -1410,6 +1427,10 @@ static int switch_output_setup(struct record *rec)
enabled:
rec->timestamp_filename = true;
s->enabled = true;
+
+ if (s->size && !rec->opts.no_buffering)
+ switch_output_size_warn(rec);
+
return 0;
}

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 435ff1c94a66..9900ce5177bc 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1184,7 +1184,7 @@ unsigned long perf_event_mlock_kb_in_pages(void)
return pages;
}

-static size_t perf_evlist__mmap_size(unsigned long pages)
+size_t perf_evlist__mmap_size(unsigned long pages)
{
if (pages == UINT_MAX)
pages = perf_event_mlock_kb_in_pages();
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 4fd034f22d2f..389b9ccdf8c7 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -218,6 +218,8 @@ int perf_evlist__mmap(struct perf_evlist *evlist, unsigned int pages,
bool overwrite);
void perf_evlist__munmap(struct perf_evlist *evlist);

+size_t perf_evlist__mmap_size(unsigned long pages);
+
void perf_evlist__disable(struct perf_evlist *evlist);
void perf_evlist__enable(struct perf_evlist *evlist);
void perf_evlist__toggle_enable(struct perf_evlist *evlist);
--
2.7.4
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