lkml.org 
[lkml]   [2018]   [Nov]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 07/12] perf top: Use cond variable instead of the lock
Date
Using conditional variable logic to synchronize between
reading and processing threads. Currently it's done by
having mutex around rotation code.

Using posix cond variable to sync both threads after queues
rotation:

process thread:
- detects data
- switches queues
- set rotate variable
- waits in pthread_cond_wait

read thread:
- detects rotate is set
- kicks process thread with pthread_cond_signal

After this rotation is safely completed and both threads
can continue with the new queue.

Link: http://lkml.kernel.org/n/tip-3rdeg23rv3brvy1pwt3igvyw@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/perf/builtin-top.c | 24 +++++++++++++++++-------
tools/perf/util/top.h | 4 +++-
2 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index f8dcdf0f54e1..ca2a1557ac07 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)
@@ -1272,6 +1281,7 @@ 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);
diff --git a/tools/perf/util/top.h b/tools/perf/util/top.h
index 5f503293cfd8..5bce62ebcf14 100644
--- a/tools/perf/util/top.h
+++ b/tools/perf/util/top.h
@@ -44,7 +44,9 @@ struct perf_top {
struct {
struct ordered_events *in;
struct ordered_events data[2];
- pthread_mutex_t lock;
+ bool rotate;
+ pthread_mutex_t mutex;
+ pthread_cond_t cond;
} qe;
};

--
2.17.2
\
 
 \ /
  Last update: 2018-11-19 13:22    [W:0.089 / U:1.472 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site