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perf evlist: Do not use hard coded value for a mmap_pages default

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So far what is in there by default is what we were using: 512KB + the
control page, but the admin may change that, and if it does to a smaller
value, all calls to tooling for non root users start failing, requiring
that the user manually set --mmap_pages/-m.

Use instead what is in /proc/sys/kernel/perf_event_mlock_kb.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-2f6mtm8xu3wo5lhkql6jdblh@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo 2014-12-12 17:46:45 -03:00
parent 38d5447d64
commit 8185e881f9
1 changed files with 16 additions and 4 deletions
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20
tools/perf/util/evlist.c
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@ -893,10 +893,22 @@ static int perf_evlist__mmap_per_thread(struct perf_evlist *evlist,
static size_t perf_evlist__mmap_size(unsigned long pages)
{
/* 512 kiB: default amount of unprivileged mlocked memory */
if (pages == UINT_MAX)
pages = (512 * 1024) / page_size;
else if (!is_power_of_2(pages))
if (pages == UINT_MAX) {
int max;
if (sysctl__read_int("kernel/perf_event_mlock_kb", &max) < 0) {
/*
* Pick a once upon a time good value, i.e. things look
* strange since we can't read a sysctl value, but lets not
* die yet...
*/
max = 512;
} else {
max -= (page_size / 1024);
}
pages = (max * 1024) / page_size;
} else if (!is_power_of_2(pages))
return 0;
return (pages + 1) * page_size;