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From: Riccardo Mancini <rickyman7@gmail.com>
To: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Ian Rogers <irogers@google.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Mark Rutland <mark.rutland@arm.com>, Jiri Olsa <jolsa@redhat.com>,
	linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
	Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com>,
	Riccardo Mancini <rickyman7@gmail.com>
Subject: [RFC PATCH v3 09/15] perf workqueue: spinup threads when needed
Date: Fri, 20 Aug 2021 12:53:55 +0200	[thread overview]
Message-ID: <c50a4628b86c445391014fb16709c11f72082454.1629454773.git.rickyman7@gmail.com> (raw)
In-Reply-To: <cover.1629454773.git.rickyman7@gmail.com>

This patch adds lazy thread creation in the workqueue.
When a new work is submitted, first an idle worker is searched. If one
is found, it will be selected for execution. Otherwise, a not already
spawned thread is searched. If found, it will be spun up and selected.
If none of the latter is found, one of the busy threads is chosen using
a round-robin policy.

Signed-off-by: Riccardo Mancini <rickyman7@gmail.com>
---
 tools/perf/util/workqueue/workqueue.c | 54 +++++++++++++++++++--------
 1 file changed, 38 insertions(+), 16 deletions(-)

diff --git a/tools/perf/util/workqueue/workqueue.c b/tools/perf/util/workqueue/workqueue.c
index 1092ece9ad39d6d2..305a9cda39810b84 100644
--- a/tools/perf/util/workqueue/workqueue.c
+++ b/tools/perf/util/workqueue/workqueue.c
@@ -39,6 +39,7 @@ struct workqueue_struct {
 	int			msg_pipe[2];	/* main thread comm pipes */
 	struct worker		**workers;	/* array of all workers */
 	struct worker		*next_worker;	/* next worker to choose (round robin) */
+	int			first_stopped_worker; /* next worker to start if needed */
 };
 
 static const char * const workqueue_errno_str[] = {
@@ -423,8 +424,7 @@ static void worker_thread(int tidx, struct task_struct *task)
  */
 struct workqueue_struct *create_workqueue(int nr_threads)
 {
-	int ret, err = 0, t;
-	struct worker *worker;
+	int ret, err = 0;
 	struct workqueue_struct *wq = zalloc(sizeof(struct workqueue_struct));
 
 	if (!wq) {
@@ -474,24 +474,11 @@ struct workqueue_struct *create_workqueue(int nr_threads)
 		goto out_close_pipe;
 	}
 
-	for (t = 0; t < nr_threads; t++) {
-		err = spinup_worker(wq, t);
-		if (err)
-			goto out_stop_pool;
-	}
-
 	wq->next_worker = NULL;
+	wq->first_stopped_worker = 0;
 
 	return wq;
 
-out_stop_pool:
-	lock_workqueue(wq);
-	for_each_idle_worker(wq, worker) {
-		ret = stop_worker(worker);
-		if (ret)
-			err = ret;
-	}
-	unlock_workqueue(wq);
 out_close_pipe:
 	close(wq->msg_pipe[0]);
 	wq->msg_pipe[0] = -1;
@@ -686,10 +673,28 @@ __releases(&worker->lock)
  */
 int queue_work(struct workqueue_struct *wq, struct work_struct *work)
 {
+	int ret;
 	struct worker *worker;
 
+repeat:
 	lock_workqueue(wq);
 	if (list_empty(&wq->idle_list)) {
+		// find a worker to spin up
+		while (wq->first_stopped_worker < threadpool__size(wq->pool)
+				&& wq->workers[wq->first_stopped_worker])
+			wq->first_stopped_worker++;
+
+		// found one
+		if (wq->first_stopped_worker < threadpool__size(wq->pool)) {
+			// spinup does not hold the lock to make the thread register itself
+			unlock_workqueue(wq);
+			ret = spinup_worker(wq, wq->first_stopped_worker);
+			if (ret)
+				return ret;
+			// worker is now in idle_list
+			goto repeat;
+		}
+
 		worker = wq->next_worker;
 		advance_next_worker(wq);
 	} else {
@@ -705,7 +710,24 @@ int queue_work(struct workqueue_struct *wq, struct work_struct *work)
  */
 int queue_work_on_worker(int tidx, struct workqueue_struct *wq, struct work_struct *work)
 {
+	int ret;
+
 	lock_workqueue(wq);
+	if (!wq->workers[tidx]) {
+		// spinup does not hold the lock to make the thread register itself
+		unlock_workqueue(wq);
+		ret = spinup_worker(wq, tidx);
+		if (ret)
+			return ret;
+
+		// now recheck if worker is available
+		lock_workqueue(wq);
+		if (!wq->workers[tidx]) {
+			unlock_workqueue(wq);
+			return -WORKQUEUE_ERROR__NOTREADY;
+		}
+	}
+
 	lock_worker(wq->workers[tidx]);
 	return __queue_work_on_worker(wq, wq->workers[tidx], work);
 }
-- 
2.31.1


  parent reply	other threads:[~2021-08-20 10:54 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-20 10:53 [RFC PATCH v3 00/15] perf: add workqueue library and use it in synthetic-events Riccardo Mancini
2021-08-20 10:53 ` [RFC PATCH v3 01/15] perf workqueue: threadpool creation and destruction Riccardo Mancini
2021-08-20 10:53 ` [RFC PATCH v3 02/15] perf tests: add test for workqueue Riccardo Mancini
2021-08-20 10:53 ` [RFC PATCH v3 03/15] perf workqueue: add threadpool start and stop functions Riccardo Mancini
2021-08-20 10:53 ` [RFC PATCH v3 04/15] perf workqueue: add threadpool execute and wait functions Riccardo Mancini
2021-08-20 10:53 ` [RFC PATCH v3 05/15] tools: add sparse context/locking annotations in compiler-types.h Riccardo Mancini
2021-08-20 10:53 ` [RFC PATCH v3 06/15] perf workqueue: introduce workqueue struct Riccardo Mancini
2021-08-24 19:27   ` Namhyung Kim
2021-08-31 16:13     ` Riccardo Mancini
2021-08-20 10:53 ` [RFC PATCH v3 07/15] perf workqueue: implement worker thread and management Riccardo Mancini
2021-08-30  7:22   ` Jiri Olsa
2021-08-20 10:53 ` [RFC PATCH v3 08/15] perf workqueue: add queue_work and flush_workqueue functions Riccardo Mancini
2021-08-24 19:40   ` Namhyung Kim
2021-08-31 16:23     ` Riccardo Mancini
2021-08-20 10:53 ` Riccardo Mancini [this message]
2021-08-20 10:53 ` [RFC PATCH v3 10/15] perf workqueue: create global workqueue Riccardo Mancini
2021-08-20 10:53 ` [RFC PATCH v3 11/15] perf workqueue: add utility to execute a for loop in parallel Riccardo Mancini
2021-08-20 10:53 ` [RFC PATCH v3 12/15] perf record: setup global workqueue Riccardo Mancini
2021-08-20 10:53 ` [RFC PATCH v3 13/15] perf top: " Riccardo Mancini
2021-08-20 10:54 ` [RFC PATCH v3 14/15] perf test/synthesis: " Riccardo Mancini
2021-08-20 10:54 ` [RFC PATCH v3 15/15] perf synthetic-events: use workqueue parallel_for Riccardo Mancini
2021-08-29 21:59 ` [RFC PATCH v3 00/15] perf: add workqueue library and use it in synthetic-events Jiri Olsa
2021-08-31 15:46   ` Jiri Olsa
2021-08-31 16:57     ` Riccardo Mancini

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