On Tue, Nov 05, 2013 at 10:28:38AM +0200, Adrian Hunter wrote: > On 04/11/13 17:29, Jiri Olsa wrote: > > On Fri, Nov 01, 2013 at 03:51:34PM +0200, Adrian Hunter wrote: > >> By default, when tasks are specified (i.e. -p, -t > >> or -u options) per-thread mmaps are created. Add > >> an option to override that and force per-cpu mmaps. > >> > >> Signed-off-by: Adrian Hunter <[email protected]> > >> --- > >> tools/perf/Documentation/perf-record.txt | 6 ++++++ > >> tools/perf/builtin-record.c | 2 ++ > >> tools/perf/util/evlist.c | 4 +++- > >> tools/perf/util/evsel.c | 4 ++-- > >> tools/perf/util/target.h | 1 + > >> 5 files changed, 14 insertions(+), 3 deletions(-) > >> > >> diff --git a/tools/perf/Documentation/perf-record.txt > >> b/tools/perf/Documentation/perf-record.txt > >> index f10ab63..2ea6685 100644 > >> --- a/tools/perf/Documentation/perf-record.txt > >> +++ b/tools/perf/Documentation/perf-record.txt > >> @@ -189,6 +189,12 @@ abort events and some memory events in precise mode > >> on modern Intel CPUs. > >> --transaction:: > >> Record transaction flags for transaction related events. > >> > >> +--force-per-cpu:: > >> +Force the use of per-cpu mmaps. By default, when tasks are specified > >> (i.e. -p, > >> +-t or -u options) per-thread mmaps are created. This option overrides > >> that and > >> +forces per-cpu mmaps. A side-effect of that is that inheritance is > >> +automatically enabled. Add the -i option also to disable inheritance. > > > > I recently sent out patch that actually force perf cpu mmaps for -p,-t,-u > > http://marc.info/?l=linux-kernel&m=138332119912433&w=2 > > > > Is there a reason why would you want to keep single > > mmap (in record command) and cut yourself from inherited > > events? > > Not sure I understand the question. > > perf supports having a single context for a thread. That is a > feature. You seem to be removing perf tools support for it. > > I image a case where the user has hundreds of CPUs but just > wants to record one thread. Currently -t does that. i.e. > one file descriptor and one mmap saving megabytes of memory. > > Another advantage of per-thread mmaps is that you do not > need to sample time (nor cpu), because the events are recorded > in order. > > I was adding a feature. Users can choose per-cpu mmaps if > they want.
right, I haven't considered the hundreds CPU machine.. I just saw that it disables inherited events in my test ;-) maybe we could mentioned that somewhere, because it's not clear jirka -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
