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Subject[tip:perf/core] perf evsel: Handle ENOMEM for perf_event_max_stack + PERF_SAMPLE_CALLCHAIN
Commit-ID:  de46d5268c4ec5c5b473c96fbf56ece188a6ba85
Gitweb: http://git.kernel.org/tip/de46d5268c4ec5c5b473c96fbf56ece188a6ba85
Author: Arnaldo Carvalho de Melo <acme@redhat.com>
AuthorDate: Wed, 27 Apr 2016 17:51:45 -0300
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Thu, 28 Apr 2016 09:58:58 -0300

perf evsel: Handle ENOMEM for perf_event_max_stack + PERF_SAMPLE_CALLCHAIN

When the kernel allows tweaking perf_event_max_stack and the event being
setup has PERF_SAMPLE_CALLCHAIN in its perf_event_attr.sample_type, tell
the user that tweaking /proc/sys/kernel/perf_event_max_stack may solve
the problem.

Before:

# echo 32000 > /proc/sys/kernel/perf_event_max_stack
# perf record -g usleep 1
Error:
The sys_perf_event_open() syscall returned with 12 (Cannot allocate memory) for event (cycles:ppp).
/bin/dmesg may provide additional information.
No CONFIG_PERF_EVENTS=y kernel support configured?

#

After:

# echo 64000 > /proc/sys/kernel/perf_event_max_stack
# perf record -g usleep 1
Error:
Not enough memory to setup event with callchain.
Hint: Try tweaking /proc/sys/kernel/perf_event_max_stack
Hint: Current value: 64000
#

Suggested-by: David Ahern <dsahern@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-ebv0orelj1s1ye857vhb82ov@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/evsel.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 334364e2..9bed7f4 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2325,6 +2325,14 @@ int perf_evsel__open_strerror(struct perf_evsel *evsel, struct target *target,
"Probably the maximum number of open file descriptors has been reached.\n"
"Hint: Try again after reducing the number of events.\n"
"Hint: Try increasing the limit with 'ulimit -n <limit>'");
+ case ENOMEM:
+ if ((evsel->attr.sample_type & PERF_SAMPLE_CALLCHAIN) != 0 &&
+ access("/proc/sys/kernel/perf_event_max_stack", F_OK) == 0)
+ return scnprintf(msg, size,
+ "Not enough memory to setup event with callchain.\n"
+ "Hint: Try tweaking /proc/sys/kernel/perf_event_max_stack\n"
+ "Hint: Current value: %d", sysctl_perf_event_max_stack);
+ break;
case ENODEV:
if (target->cpu_list)
return scnprintf(msg, size, "%s",
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