From 94ad6e7e3606454498aeac1fdd1b9de5c1e6735a Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Mon, 5 Nov 2018 21:23:40 +0100 Subject: perf top: Use cond variable instead of a lock Use conditional variable logic to synchronize between the reading and processing threads. Currently it's done by having mutex around rotation code. Using a POSIX cond variable to sync both threads after queues rotation: Process thread: - Detects data - Switches queues - Sets rotate variable - Waits in pthread_cond_wait() Read thread: - Detects rotate is set - Kicks the process thread with a pthread_cond_signal() After this rotation is safely completed and both threads can continue with the new queue. Signed-off-by: Jiri Olsa Acked-by: David S. Miller Acked-by: Namhyung Kim Tested-by: Arnaldo Carvalho de Melo Cc: Alexander Shishkin Cc: Peter Zijlstra Link: http://lkml.kernel.org/n/tip-3rdeg23rv3brvy1pwt3igvyw@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-top.c | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-) (limited to 'tools/perf/builtin-top.c') diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c index 75afeae7f04d..aad58643102e 100644 --- a/tools/perf/builtin-top.c +++ b/tools/perf/builtin-top.c @@ -846,13 +846,18 @@ static void perf_top__mmap_read_idx(struct perf_top *top, int idx) if (ret && ret != -1) break; - pthread_mutex_lock(&top->qe.lock); ret = ordered_events__queue(top->qe.in, event, timestamp, 0); - pthread_mutex_unlock(&top->qe.lock); - - perf_mmap__consume(md); if (ret) break; + + perf_mmap__consume(md); + + if (top->qe.rotate) { + pthread_mutex_lock(&top->qe.mutex); + top->qe.rotate = false; + pthread_cond_signal(&top->qe.cond); + pthread_mutex_unlock(&top->qe.mutex); + } } perf_mmap__read_done(md); @@ -1059,9 +1064,12 @@ static void *process_thread(void *arg) continue; } - pthread_mutex_lock(&top->qe.lock); out = rotate_queues(top); - pthread_mutex_unlock(&top->qe.lock); + + pthread_mutex_lock(&top->qe.mutex); + top->qe.rotate = true; + pthread_cond_wait(&top->qe.cond, &top->qe.mutex); + pthread_mutex_unlock(&top->qe.mutex); if (ordered_events__flush(out, OE_FLUSH__TOP)) pr_err("failed to process events\n"); @@ -1151,7 +1159,8 @@ static void init_process_thread(struct perf_top *top) ordered_events__set_copy_on_queue(&top->qe.data[0], true); ordered_events__set_copy_on_queue(&top->qe.data[1], true); top->qe.in = &top->qe.data[0]; - pthread_mutex_init(&top->qe.lock, NULL); + pthread_mutex_init(&top->qe.mutex, NULL); + pthread_cond_init(&top->qe.cond, NULL); } static int __cmd_top(struct perf_top *top) @@ -1271,6 +1280,7 @@ static int __cmd_top(struct perf_top *top) out_join: pthread_join(thread, NULL); out_join_thread: + pthread_cond_signal(&top->qe.cond); pthread_join(thread_process, NULL); out_delete: perf_session__delete(top->session); -- cgit v1.2.3