Commit e5adfc3e authored by Konstantin Khlebnikov's avatar Konstantin Khlebnikov Committed by Arnaldo Carvalho de Melo

perf map: Synthesize maps only for thread group leader

Threads share map_groups, all map events are merged into it.

Thus we could send mmaps only for thread group leader.  Otherwise it
took ages to attach and record something from processes with many vmas
and threads.

Thread group leader could be already dead, but it seems perf cannot
handle this case anyway.

Testing dummy:

  #include <stdio.h>
  #include <stdlib.h>
  #include <sys/mman.h>
  #include <pthread.h>
  #include <unistd.h>

  void *thread(void *arg) {
          pause();
  }

  int main(int argc, char **argv) {
        int threads = 10000;
        int vmas = 50000;
        pthread_t th;
        for (int i = 0; i < threads; i++)
                pthread_create(&th, NULL, thread, NULL);
        for (int i = 0; i < vmas; i++)
                mmap(NULL, 4096, (i & 1) ? PROT_READ : PROT_WRITE,
                     MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0);
        sleep(60);
        return 0;
  }

Comment by Jiri Olsa:

We actualy synthesize the group leader (if we found one) for the thread
even if it's not present in the thread_map, so the process maps are
always in data.
Signed-off-by: default avatarKonstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: default avatarJiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/153363294102.396323.6277944760215058174.stgit@buzzSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 88cf7084
......@@ -541,10 +541,17 @@ static int __event__synthesize_thread(union perf_event *comm_event,
tgid, process, machine) < 0)
return -1;
return perf_event__synthesize_mmap_events(tool, mmap_event, pid, tgid,
/*
* send mmap only for thread group leader
* see thread__init_map_groups
*/
if (pid == tgid &&
perf_event__synthesize_mmap_events(tool, mmap_event, pid, tgid,
process, machine, mmap_data,
proc_map_timeout);
proc_map_timeout))
return -1;
return 0;
}
if (machine__is_default_guest(machine))
......
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