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perf top: Use cond variable instead of a lock

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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 <jolsa@kernel.org>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-3rdeg23rv3brvy1pwt3igvyw@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Jiri Olsa 2018-11-05 21:23:40 +01:00 committed by Arnaldo Carvalho de Melo
parent 16c66bc167
commit 94ad6e7e36
2 changed files with 20 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
tools/perf/builtin-top.c
View File

@ -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);

4
tools/perf/util/top.h
View File

@ -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;
};