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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9C01CC54EE9 for ; Sun, 18 Sep 2022 11:39:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229600AbiIRLjW (ORCPT ); Sun, 18 Sep 2022 07:39:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42090 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229912AbiIRLjB (ORCPT ); Sun, 18 Sep 2022 07:39:01 -0400 Received: from out0.migadu.com (out0.migadu.com [IPv6:2001:41d0:2:267::]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6D10D27DD3; Sun, 18 Sep 2022 04:38:57 -0700 (PDT) Subject: Re: [PATCH v3 3/5] md/raid10: prevent unnecessary calls to wake_up() in fast path DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1663501136; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=RV6OPhI8PJKT5vEl51soNB+bv12n4mODtQRF3wFhIqY=; b=r0jOjpGO8JWFpzyL87wflqGOOqZrFuTd+sgMqSwQYNhIjWVUzwtE8Ef+COLFd6hA1lJ7vK 0xp+K3NbPqmaHIeX7UKBk9wyujRiABMED+ddpV5W7uOWrxhXag35+0glUENMi6ORwA62P2 LxzlXkH4FqrFD/lc8mzIiCsmJvTA5eg= To: Yu Kuai , song@kernel.org, logang@deltatee.com, pmenzel@molgen.mpg.de Cc: linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, yukuai3@huawei.com, yi.zhang@huawei.com References: <20220916113428.774061-1-yukuai1@huaweicloud.com> <20220916113428.774061-4-yukuai1@huaweicloud.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Guoqing Jiang Message-ID: <5f2b0c5d-209b-9c0c-ff22-781542d5517e@linux.dev> Date: Sun, 18 Sep 2022 19:38:50 +0800 MIME-Version: 1.0 In-Reply-To: <20220916113428.774061-4-yukuai1@huaweicloud.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org On 9/16/22 7:34 PM, Yu Kuai wrote: > From: Yu Kuai > > Currently, wake_up() is called unconditionally in fast path such as > raid10_make_request(), which will cause lock contention under high > concurrency: > > raid10_make_request > wake_up > __wake_up_common_lock > spin_lock_irqsave > > Improve performance by only call wake_up() if waitqueue is not empty > in allow_barrier() and raid10_make_request(). > > Signed-off-by: Yu Kuai > --- > drivers/md/raid10.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c > index df435d693637..cf452c25e1e5 100644 > --- a/drivers/md/raid10.c > +++ b/drivers/md/raid10.c > @@ -274,6 +274,12 @@ static void put_buf(struct r10bio *r10_bio) > lower_barrier(conf); > } > > +static void wake_up_barrier(struct r10conf *conf) > +{ > + if (wq_has_sleeper(&conf->wait_barrier)) > + wake_up(&conf->wait_barrier); > +} > + > static void reschedule_retry(struct r10bio *r10_bio) > { > unsigned long flags; > @@ -1015,7 +1021,7 @@ static void allow_barrier(struct r10conf *conf) > { > if ((atomic_dec_and_test(&conf->nr_pending)) || > (conf->array_freeze_pending)) > - wake_up(&conf->wait_barrier); > + wake_up_barrier(conf); > } > > static void freeze_array(struct r10conf *conf, int extra) > @@ -1891,7 +1897,7 @@ static bool raid10_make_request(struct mddev *mddev, struct bio *bio) > __make_request(mddev, bio, sectors); > > /* In case raid10d snuck in to freeze_array */ > - wake_up(&conf->wait_barrier); > + wake_up_barrier(conf); > return true; > } > Acked-by: Guoqing Jiang Thanks, Guoqing