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 EB66FC43217 for ; Tue, 5 Apr 2022 11:06:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347349AbiDELCB (ORCPT ); Tue, 5 Apr 2022 07:02:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45572 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234768AbiDEIjT (ORCPT ); Tue, 5 Apr 2022 04:39:19 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A02D821802; Tue, 5 Apr 2022 01:33:03 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 36FADB81A32; Tue, 5 Apr 2022 08:33:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6F263C385A0; Tue, 5 Apr 2022 08:33:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649147580; bh=aFHFFMUipHtG2lH2cH1iKH9i2DXXPKMIpLsnTSvrAjc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ea+Em23vH2+LlNZg6SuEIUl/C4kE9sgPEk0iHIeJ60CLZNpcoYSiNHUl0eZGxDAvK W67coiOw2dMiRkntxYueSpXRi6sHzCUU4RMs6VIEQ1VRwGaPOgOkf7imLHJFJM8801 oQS7YHln+QaDpxObdHf5Inwt0Sn8JGcV67h67f4U= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Song Liu , Jens Axboe , Song Liu Subject: [PATCH 5.16 0030/1017] block: ensure plug merging checks the correct queue at least once Date: Tue, 5 Apr 2022 09:15:43 +0200 Message-Id: <20220405070355.072987835@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220405070354.155796697@linuxfoundation.org> References: <20220405070354.155796697@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jens Axboe commit 5b2050718d095cd3242d1f42aaaea3a2fec8e6f0 upstream. Song reports that a RAID rebuild workload runs much slower recently, and it is seeing a lot less merging than it did previously. The reason is that a previous commit reduced the amount of work we do for plug merging. RAID rebuild interleaves requests between disks, so a last-entry check in plug merging always misses a merge opportunity since we always find a different disk than what we are looking for. Modify the logic such that it's still a one-hit cache, but ensure that we check enough to find the right target before giving up. Fixes: d38a9c04c0d5 ("block: only check previous entry for plug merge attempt") Reported-and-tested-by: Song Liu Reviewed-by: Song Liu Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/blk-merge.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-) --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -1093,18 +1093,21 @@ bool blk_attempt_plug_merge(struct reque if (!plug || rq_list_empty(plug->mq_list)) return false; - /* check the previously added entry for a quick merge attempt */ - rq = rq_list_peek(&plug->mq_list); - if (rq->q == q) { + rq_list_for_each(&plug->mq_list, rq) { + if (rq->q == q) { + *same_queue_rq = true; + if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) == + BIO_MERGE_OK) + return true; + break; + } + /* - * Only blk-mq multiple hardware queues case checks the rq in - * the same queue, there should be only one such rq in a queue + * Only keep iterating plug list for merges if we have multiple + * queues */ - *same_queue_rq = true; - - if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) == - BIO_MERGE_OK) - return true; + if (!plug->multiple_queues) + break; } return false; }