From 8185e881f9fd9a2fa01f9d45616f8587f485f2a6 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Fri, 12 Dec 2014 17:46:45 -0300 Subject: [PATCH] perf evlist: Do not use hard coded value for a mmap_pages default 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 Cc: Borislav Petkov Cc: David Ahern Cc: Don Zickus Cc: Frederic Weisbecker Cc: Jiri Olsa Cc: Mike Galbraith Cc: Namhyung Kim Cc: Paul Mackerras Cc: Peter Zijlstra Cc: Stephane Eranian Link: http://lkml.kernel.org/n/tip-2f6mtm8xu3wo5lhkql6jdblh@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/evlist.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c index 7847f3885081..ac808680e61c 100644 --- a/tools/perf/util/evlist.c +++ b/tools/perf/util/evlist.c @@ -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;