From patchwork Fri Oct 28 22:52:35 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Shaohua Li X-Patchwork-Id: 9402805 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 93CC56022E for ; Fri, 28 Oct 2016 22:52:59 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 839F22A8D6 for ; Fri, 28 Oct 2016 22:52:59 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 771D22A8DB; Fri, 28 Oct 2016 22:52:59 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI,T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id F34C92A8D6 for ; Fri, 28 Oct 2016 22:52:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761424AbcJ1Wwl (ORCPT ); Fri, 28 Oct 2016 18:52:41 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:40583 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756769AbcJ1Wwk (ORCPT ); Fri, 28 Oct 2016 18:52:40 -0400 Received: from pps.filterd (m0044010.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id u9SMnVE4006337 for ; Fri, 28 Oct 2016 15:52:39 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=fb.com; h=from : to : cc : subject : date : message-id : mime-version : content-type; s=facebook; bh=fVrA5XJI3topzSrfhdBJz3EVgixGgNh+SkJ02KMFB3Y=; b=JjMG11gVXPg7YAHFtCA4MvJyu3ZDi1n+96hzqnweMZ59R55yoibsYFX3VdMv70GFgo/k j0zGPMuYGVQ3aqQt6GujvzuP0iEEdbWbDXorjapkJ+wv69RsUJDM/F/qWkdh+cKqyw/4 WbXuk6+V6U2mmXnMQZaDIE1nQoZWChODLg0= Received: from mail.thefacebook.com ([199.201.64.23]) by mx0a-00082601.pphosted.com with ESMTP id 26c9u5bn08-1 (version=TLSv1 cipher=ECDHE-RSA-AES256-SHA bits=256 verify=NOT) for ; Fri, 28 Oct 2016 15:52:39 -0700 Received: from mx-out.facebook.com (192.168.52.123) by PRN-CHUB14.TheFacebook.com (192.168.16.24) with Microsoft SMTP Server (TLS) id 14.3.294.0; Fri, 28 Oct 2016 15:52:38 -0700 Received: from facebook.com (2401:db00:21:603d:face:0:19:0) by mx-out.facebook.com (10.222.219.45) with ESMTP id 38f1ab7a9d6111e6a3a124be05904660-519eda50 for ; Fri, 28 Oct 2016 15:52:37 -0700 Received: by devbig638.prn2.facebook.com (Postfix, from userid 11222) id E137142C5978; Fri, 28 Oct 2016 15:52:36 -0700 (PDT) From: Shaohua Li To: , CC: , Subject: [PATCH 1/2] block: immediately dispatch big size request Date: Fri, 28 Oct 2016 15:52:35 -0700 Message-ID: X-Mailer: git-send-email 2.9.3 X-FB-Internal: Safe MIME-Version: 1.0 X-Proofpoint-Spam-Reason: safe X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2016-10-28_12:, , signatures=0 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Currently block plug holds up to 16 non-mergeable requests. This makes sense if the request size is small, eg, reduce lock contention. But if request size is big enough, we don't need to worry about lock contention. Holding such request makes no sense and it lows the disk utilization. In practice, this improves 10% throughput for my raid5 sequential write workload. The size (128k) is arbitrary right now, but it makes sure lock contention is small. This probably could be more intelligent, eg, check average request size holded. Since this is mainly for sequential IO, probably not worthy. Signed-off-by: Shaohua Li --- block/blk-core.c | 4 +++- include/linux/blkdev.h | 1 + 2 files changed, 4 insertions(+), 1 deletion(-) diff --git a/block/blk-core.c b/block/blk-core.c index 14d7c07..0a396e9 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1763,7 +1763,9 @@ static blk_qc_t blk_queue_bio(struct request_queue *q, struct bio *bio) if (!request_count) trace_block_plug(q); else { - if (request_count >= BLK_MAX_REQUEST_COUNT) { + struct request *first = list_entry_rq(plug->list.next); + if (request_count >= BLK_MAX_REQUEST_COUNT || + blk_rq_bytes(first) >= BLK_PLUG_FLUSH_SIZE) { blk_flush_plug_list(plug, false); trace_block_plug(q); } diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index c47c358..72fa505 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -1078,6 +1078,7 @@ struct blk_plug { struct list_head cb_list; /* md requires an unplug callback */ }; #define BLK_MAX_REQUEST_COUNT 16 +#define BLK_PLUG_FLUSH_SIZE (128 * 1024) struct blk_plug_cb; typedef void (*blk_plug_cb_fn)(struct blk_plug_cb *, bool);