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perf: mmap 512 kiB by default 

The default setting of perf record is to mmap 128 pages if the user
did not override with -m.

However the page size may vary accross different architecture
settings, giving different default size between each.

Moreover the kernel side still has a default max number of mlocked
pages of 512 kiB + 1 page for unprivileged users. 128 + 1 pages
with page size > 4096 overlaps this threshold.

Thus, better adapt to this limitation and set the default number of
pages to fit those 512 kiB + 1 page.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <1301535324-9735-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Frederic Weisbecker 2011-03-31 03:35:24 +02:00 committed by Ingo Molnar
parent 20443384fe
commit 800cd25c12
1 changed files with 5 additions and 1 deletions
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6
tools/perf/builtin-record.c
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@ -41,7 +41,7 @@ static u64 user_interval = ULLONG_MAX;
static u64 default_interval = 0;
static unsigned int page_size;
static unsigned int mmap_pages = 128;
static unsigned int mmap_pages = UINT_MAX;
static unsigned int user_freq = UINT_MAX;
static int freq = 1000;
static int output;
@ -513,6 +513,10 @@ static int __cmd_record(int argc, const char **argv)
if (have_tracepoints(&evsel_list->entries))
perf_header__set_feat(&session->header, HEADER_TRACE_INFO);
/* 512 kiB: default amount of unprivileged mlocked memory */
if (mmap_pages == UINT_MAX)
mmap_pages = (512 * 1024) / page_size;
if (forks) {
child_pid = fork();
if (child_pid < 0) {