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=-5.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 2CF34C3F2D1 for ; Wed, 4 Mar 2020 09:54:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0235D20848 for ; Wed, 4 Mar 2020 09:54:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="OYHmm/KV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728301AbgCDJyA (ORCPT ); Wed, 4 Mar 2020 04:54:00 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:51107 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726137AbgCDJyA (ORCPT ); Wed, 4 Mar 2020 04:54:00 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1583315639; 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: in-reply-to:in-reply-to:references:references; bh=FkzB3yG0y0Ged2g2RW6JaU0gQCmiCHVS4oMg7bWHstw=; b=OYHmm/KVimM6z/zrBYVXV9xPzGhHJOnktPJ2cgudWHPXYqFdXtnAq0mlKy/eNSnD1bQr52 AGMjucyZoE0VI8YIkxfT7TodAZj/4401k82wa2VnLhEofMJC+R+4sVgSSHvE93NlGJD39i ELXpr3mxUsXEkY4L8adhhZniGPLtlio= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-335-PFEqAbAzP1qEyJiB0uroBA-1; Wed, 04 Mar 2020 04:53:56 -0500 X-MC-Unique: PFEqAbAzP1qEyJiB0uroBA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AF6751005510; Wed, 4 Mar 2020 09:53:54 +0000 (UTC) Received: from ming.t460p (ovpn-8-28.pek2.redhat.com [10.72.8.28]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3F22E8F34A; Wed, 4 Mar 2020 09:53:48 +0000 (UTC) Date: Wed, 4 Mar 2020 17:53:44 +0800 From: Ming Lei To: Shinichiro Kawasaki Cc: "linux-block@vger.kernel.org" , Jens Axboe , Damien Le Moal Subject: Re: commit 01e99aeca397 causes longer runtime of block/004 Message-ID: <20200304095344.GA10390@ming.t460p> References: <20200304023842.gu37d4mzfbseiscw@shindev.dhcp.fujisawa.hgst.com> <20200304034644.GA23012@ming.t460p> <20200304061137.l4hdqdt2dvs7dxgz@shindev.dhcp.fujisawa.hgst.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200304061137.l4hdqdt2dvs7dxgz@shindev.dhcp.fujisawa.hgst.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed, Mar 04, 2020 at 06:11:37AM +0000, Shinichiro Kawasaki wrote: > On Mar 04, 2020 / 11:46, Ming Lei wrote: > > On Wed, Mar 04, 2020 at 02:38:43AM +0000, Shinichiro Kawasaki wrote: > > > I noticed that blktests block/004 takes longer runtime with 5.6-rc4 than > > > 5.6-rc3, and found that the commit 01e99aeca397 ("blk-mq: insert passthrough > > > request into hctx->dispatch directly") triggers it. > > > > > > The longer runtime was observed with dm-linear device which maps SATA SMR HDD > > > connected via AHCI. It was not observed with dm-linear on SAS/SATA SMR HDDs > > > connected via SAS-HBA. Not observed with dm-linear on non-SMR HDDs either. > > > > > > Before the commit, block/004 took around 130 seconds. After the commit, it takes > > > around 300 seconds. I need to dig in further details to understand why the > > > commit makes the test case longer. > > > > > > The test case block/004 does "flush intensive workload". Is this longer runtime > > > expected? > > > > The following patch might address this issue: > > > > https://lore.kernel.org/linux-block/20200207190416.99928-1-sqazi@google.com/#t > > > > Please test and provide us the result. > > > > thanks, > > Ming > > > > Hi Ming, > > I applied the patch to 5.6-rc4 but I observed the longer runtime of block/004. > Still it takes around 300 seconds. Hello Shinichiro, block/004 only sends 1564 sync randwrite, and seems 130s has been slow enough. There are two related effect in that commit for your issue: 1) 'at_head' is applied in blk_mq_sched_insert_request() for flush request 2) all IO is added back to tail of hctx->dispatch after .queue_rq() returns STS_RESOURCE Seems it is more related with 2) given you can't reproduce the issue on SAS. So please test the following two patches, and see which one makes a difference for you. BTW, both two looks not reasonable, just for narrowing down the issue. 1) patch 1 diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index 856356b1619e..86137c75283c 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -398,7 +398,7 @@ void blk_mq_sched_insert_request(struct request *rq, bool at_head, WARN_ON(e && (rq->tag != -1)); if (blk_mq_sched_bypass_insert(hctx, !!e, rq)) { - blk_mq_request_bypass_insert(rq, at_head, false); + blk_mq_request_bypass_insert(rq, true, false); goto run; } 2) patch 2 diff --git a/block/blk-mq.c b/block/blk-mq.c index d92088dec6c3..447d5cb39832 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1286,7 +1286,7 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list, q->mq_ops->commit_rqs(hctx); spin_lock(&hctx->lock); - list_splice_tail_init(list, &hctx->dispatch); + list_splice_init(list, &hctx->dispatch); spin_unlock(&hctx->lock); /* Thanks, Ming