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[176.243.199.7]) by smtp.googlemail.com with ESMTPSA id g29sm3451459edf.31.2021.08.20.03.54.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 20 Aug 2021 03:54:23 -0700 (PDT) From: Riccardo Mancini To: Arnaldo Carvalho de Melo Cc: Ian Rogers , Namhyung Kim , Peter Zijlstra , Ingo Molnar , Mark Rutland , Jiri Olsa , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Alexey Bayduraev , Riccardo Mancini Subject: [RFC PATCH v3 09/15] perf workqueue: spinup threads when needed Date: Fri, 20 Aug 2021 12:53:55 +0200 Message-Id: X-Mailer: git-send-email 2.31.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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