perf evlist: Do not use hard coded value for a mmap_pages default
tip-bot for Arnaldo Carvalho de Melo
merge botCommit-ID: 8185e881f9fd9a2fa01f9d45616f8587f485f2a6 Gitweb: http://git.kernel.org/tip/8185e881f9fd9a2fa01f9d45616f8587f485f2a6 Author: Arnaldo Carvalho de Melo <[email protected]> AuthorDate: Fri, 12 Dec 2014 17:46:45 -0300 Committer: Arnaldo Carvalho de Melo <[email protected]> CommitDate: Tue, 16 Dec 2014 13:38:26 -0300
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 <[email protected]>
Cc Borislav Petkov <[email protected]>
Cc David Ahern <[email protected]>
Cc Don Zickus <[email protected]>
Cc Frederic Weisbecker <[email protected]>
Cc Jiri Olsa <[email protected]>
Cc Mike Galbraith <[email protected]>
Cc Namhyung Kim <[email protected]>
Cc Paul Mackerras <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Stephane Eranian <[email protected]>
Signed-off-by Arnaldo Carvalho de Melo <[email protected]>
--- tools/perf/util/evlist.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-)
tools/perf/util/evlist.c +16 -4
@@ -893,10 +893,22 @@ out_unmap: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;