From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 93792C388F2 for ; Thu, 22 Oct 2020 05:54:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2C1E52244C for ; Thu, 22 Oct 2020 05:54:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="XxK9WczS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2503014AbgJVFya (ORCPT ); Thu, 22 Oct 2020 01:54:30 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:53998 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2409013AbgJVFya (ORCPT ); Thu, 22 Oct 2020 01:54:30 -0400 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 09M5jr5Q062940; Thu, 22 Oct 2020 05:54:28 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=corp-2020-01-29; bh=qC9nCjheFDe7QZnvbm66+cyFjZwzYcTAobNlQNLorxk=; b=XxK9WczShfV9Pb8/tJrzUhgeQpJNLAdg49pAH4SWRAmmjICxuEMok+i+P6oEi53hFKXv IiqGCQE4VUxDRpYFGiyDwnbrrdiTrX0GZVEvYs4Y3VKuotkdBsROimBH3UHCwy6kZ9FI IA5dYxJf+kYK5GtvutiJui+ApuPkJ7kLKjD3NT7d6kGKQ4btvgLAEibaop9ccK1igQjw GEfTvIE7gUBk3cr/bMzo08BfDG9B4j6HxZoVEfQ2ulZrNWnamxU6UGlbwZ/jXwNHbMrX ocyqaBtEORxbLXl+ZMD//WOD+kCil26VqfYazNrkzOwyAD0qO4WOL1AKABkjtHbkggNG WQ== Received: from userp3030.oracle.com (userp3030.oracle.com [156.151.31.80]) by aserp2120.oracle.com with ESMTP id 349jrpv2x6-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 22 Oct 2020 05:54:28 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 09M5j12o132032; Thu, 22 Oct 2020 05:54:27 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userp3030.oracle.com with ESMTP id 348ahycufx-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 22 Oct 2020 05:54:27 +0000 Received: from abhmp0018.oracle.com (abhmp0018.oracle.com [141.146.116.24]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 09M5sQ7R004999; Thu, 22 Oct 2020 05:54:26 GMT Received: from localhost (/67.169.218.210) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 21 Oct 2020 22:54:26 -0700 Date: Wed, 21 Oct 2020 22:54:25 -0700 From: "Darrick J. Wong" To: Dave Chinner Cc: linux-xfs@vger.kernel.org Subject: Re: [PATCH 1/7] workqueue: bound maximum queue depth Message-ID: <20201022055425.GN9832@magnolia> References: <20201022051537.2286402-1-david@fromorbit.com> <20201022051537.2286402-2-david@fromorbit.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201022051537.2286402-2-david@fromorbit.com> X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9781 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 phishscore=0 bulkscore=0 malwarescore=0 spamscore=0 mlxlogscore=999 mlxscore=0 suspectscore=5 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2010220039 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9781 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 lowpriorityscore=0 priorityscore=1501 impostorscore=0 adultscore=0 bulkscore=0 malwarescore=0 mlxlogscore=999 mlxscore=0 spamscore=0 suspectscore=5 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2010220039 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Thu, Oct 22, 2020 at 04:15:31PM +1100, Dave Chinner wrote: > From: Dave Chinner > > Existing users of workqueues have bound maximum queue depths in > their external algorithms (e.g. prefetch counts). For parallelising > work that doesn't have an external bound, allow workqueues to > throttle incoming requests at a maximum bound. bounded workqueues Nit: capitalize the 'B' in 'bounded'. > also need to distribute work over all worker threads themselves as > there is no external bounding or worker function throttling > provided. > > Existing callers are not throttled and retain direct control of > worker threads, only users of the new create interface will be > throttled and concurrency managed. > > Signed-off-by: Dave Chinner > --- > libfrog/workqueue.c | 42 +++++++++++++++++++++++++++++++++++++++--- > libfrog/workqueue.h | 4 ++++ > 2 files changed, 43 insertions(+), 3 deletions(-) > > diff --git a/libfrog/workqueue.c b/libfrog/workqueue.c > index fe3de4289379..e42b2a2f678b 100644 > --- a/libfrog/workqueue.c > +++ b/libfrog/workqueue.c > @@ -40,13 +40,21 @@ workqueue_thread(void *arg) > } > > /* > - * Dequeue work from the head of the list. > + * Dequeue work from the head of the list. If the queue was > + * full then send a wakeup if we're configured to do so. > */ > assert(wq->item_count > 0); > + if (wq->max_queued && wq->item_count == wq->max_queued) > + pthread_cond_signal(&wq->queue_full); > + > wi = wq->next_item; > wq->next_item = wi->next; > wq->item_count--; > > + if (wq->max_queued && wq->next_item) { > + /* more work, wake up another worker */ > + pthread_cond_signal(&wq->wakeup); Hmm. The net effect of this is that we wake up workers faster when a ton of work comes in, right? And I bet none of the current workqueue users have suffered from this because they queue a bunch of work and then call workqueue_terminate, which wakes all the threads, and they never go to sleep again. Does it make sense to simplify the test to "if (wq->next_item) {"? Other than that, looks good! --D > + } > pthread_mutex_unlock(&wq->lock); > > (wi->function)(wi->queue, wi->index, wi->arg); > @@ -58,10 +66,11 @@ workqueue_thread(void *arg) > > /* Allocate a work queue and threads. Returns zero or negative error code. */ > int > -workqueue_create( > +workqueue_create_bound( > struct workqueue *wq, > void *wq_ctx, > - unsigned int nr_workers) > + unsigned int nr_workers, > + unsigned int max_queue) > { > unsigned int i; > int err = 0; > @@ -70,12 +79,16 @@ workqueue_create( > err = -pthread_cond_init(&wq->wakeup, NULL); > if (err) > return err; > + err = -pthread_cond_init(&wq->queue_full, NULL); > + if (err) > + goto out_wake; > err = -pthread_mutex_init(&wq->lock, NULL); > if (err) > goto out_cond; > > wq->wq_ctx = wq_ctx; > wq->thread_count = nr_workers; > + wq->max_queued = max_queue; > wq->threads = malloc(nr_workers * sizeof(pthread_t)); > if (!wq->threads) { > err = -errno; > @@ -102,10 +115,21 @@ workqueue_create( > out_mutex: > pthread_mutex_destroy(&wq->lock); > out_cond: > + pthread_cond_destroy(&wq->queue_full); > +out_wake: > pthread_cond_destroy(&wq->wakeup); > return err; > } > > +int > +workqueue_create( > + struct workqueue *wq, > + void *wq_ctx, > + unsigned int nr_workers) > +{ > + return workqueue_create_bound(wq, wq_ctx, nr_workers, 0); > +} > + > /* > * Create a work item consisting of a function and some arguments and schedule > * the work item to be run via the thread pool. Returns zero or a negative > @@ -140,6 +164,7 @@ workqueue_add( > > /* Now queue the new work structure to the work queue. */ > pthread_mutex_lock(&wq->lock); > +restart: > if (wq->next_item == NULL) { > assert(wq->item_count == 0); > ret = -pthread_cond_signal(&wq->wakeup); > @@ -150,6 +175,16 @@ workqueue_add( > } > wq->next_item = wi; > } else { > + /* throttle on a full queue if configured */ > + if (wq->max_queued && wq->item_count == wq->max_queued) { > + pthread_cond_wait(&wq->queue_full, &wq->lock); > + /* > + * Queue might be empty or even still full by the time > + * we get the lock back, so restart the lookup so we do > + * the right thing with the current state of the queue. > + */ > + goto restart; > + } > wq->last_item->next = wi; > } > wq->last_item = wi; > @@ -201,5 +236,6 @@ workqueue_destroy( > free(wq->threads); > pthread_mutex_destroy(&wq->lock); > pthread_cond_destroy(&wq->wakeup); > + pthread_cond_destroy(&wq->queue_full); > memset(wq, 0, sizeof(*wq)); > } > diff --git a/libfrog/workqueue.h b/libfrog/workqueue.h > index a56d1cf14081..a9c108d0e66a 100644 > --- a/libfrog/workqueue.h > +++ b/libfrog/workqueue.h > @@ -31,10 +31,14 @@ struct workqueue { > unsigned int thread_count; > bool terminate; > bool terminated; > + int max_queued; > + pthread_cond_t queue_full; > }; > > int workqueue_create(struct workqueue *wq, void *wq_ctx, > unsigned int nr_workers); > +int workqueue_create_bound(struct workqueue *wq, void *wq_ctx, > + unsigned int nr_workers, unsigned int max_queue); > int workqueue_add(struct workqueue *wq, workqueue_func_t fn, > uint32_t index, void *arg); > int workqueue_terminate(struct workqueue *wq); > -- > 2.28.0 >