[PATCH 15/18] perf tools: Make the mmap length autotuning more robust

From: Arnaldo Carvalho de Melo
Date: Tue Dec 16 2014 - 11:59:03 EST


From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

If /proc/sys/kernel/perf_event_mlock_kb is not (power of 2 + PAGE_SIZE_in_kb)
and we let the perf tools do mmap length autosizing based on that, then, for
non-CAP_IPC_LOCK users when /proc/sys/kernel/perf_event_paranoid is > -1, then
we get an -EINVAL that ends up in:

[acme@ssdandy linux]$ trace usleep 1
Invalid argument
[acme@ssdandy linux]$ perf record usleep 1
failed to mmap with 22 (Invalid argument)

After this fix:

[acme@ssdandy linux]$ trace usleep 1
<SNIP>
0.806 ( 0.006 ms): munmap(addr: 0x7f7e4740a000, len: 66467) = 0
0.869 ( 0.002 ms): brk( ) = 0x7bb000
0.873 ( 0.003 ms): brk(brk: 0x7dc000 ) = 0x7dc000
0.877 ( 0.001 ms): brk( ) = 0x7dc000
0.953 ( 0.058 ms): nanosleep(rqtp: 0x7fff26ab9420 ) = 0
0.959 ( 0.000 ms): exit_group(
[acme@ssdandy linux]$ perf record usleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.017 MB perf.data (~759 samples) ]
[acme@ssdandy linux]$

Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Don Zickus <dzickus@xxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Link: http://lkml.kernel.org/n/tip-6p6l5ou6jev6o7ymc4nn1n2a@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/perf/util/evlist.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 8eb92cf5d552..7d88327d94a9 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -909,6 +909,8 @@ static size_t perf_evlist__mmap_size(unsigned long pages)
}

pages = (max * 1024) / page_size;
+ if (!is_power_of_2(pages))
+ pages = rounddown_pow_of_two(pages);
} else if (!is_power_of_2(pages))
return 0;

--
1.9.3

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