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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 807C1FA3728 for ; Wed, 16 Oct 2019 22:09:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 53D652168B for ; Wed, 16 Oct 2019 22:09:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571263780; bh=OuhpAZtWvGGN1P/s/XbrJ/IGUTkpi1O1QmxyxVUadR4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=C9Qfx68LpVxHYbQ86uZWrEr+YBE98qo2G1ZQydPhvh9gs62/eDu/UaEPD9GihAzve +P/fCN0ln+f9iSgfPs28OaIhBJMcEZF9cRjRCaJV12HKXPLwIjQDlzaNGSTg1rWHxh BpOa5JZ2O/aBPjBHIan6CajsOpYvp+xsXAru1/Jw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2407167AbfJPWJj (ORCPT ); Wed, 16 Oct 2019 18:09:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:50152 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2406644AbfJPV52 (ORCPT ); Wed, 16 Oct 2019 17:57:28 -0400 Received: from localhost (unknown [192.55.54.58]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5ADE621928; Wed, 16 Oct 2019 21:57:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571263047; bh=OuhpAZtWvGGN1P/s/XbrJ/IGUTkpi1O1QmxyxVUadR4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jlLBWg6mzfaaZCBIgeX/jr+E1Vp2Rr0L7w5WSqZWi1JR1MJaEc31O/RxZvCyxUw1S A0sFLy6LjUdwlvZIc8atVB5ETzWXoKmWZ9NwuWW/n48KfuLNqvBvHKa9LYbRqBJ0eS wVLIi730gsDojL2H9Uca30+hP9UnCamqKpjFTQZs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Josef Bacik , Harshad Shirwadkar , Jens Axboe Subject: [PATCH 4.19 52/81] blk-wbt: fix performance regression in wbt scale_up/scale_down Date: Wed, 16 Oct 2019 14:51:03 -0700 Message-Id: <20191016214841.239919200@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191016214805.727399379@linuxfoundation.org> References: <20191016214805.727399379@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Harshad Shirwadkar commit b84477d3ebb96294f87dc3161e53fa8fe22d9bfd upstream. scale_up wakes up waiters after scaling up. But after scaling max, it should not wake up more waiters as waiters will not have anything to do. This patch fixes this by making scale_up (and also scale_down) return when threshold is reached. This bug causes increased fdatasync latency when fdatasync and dd conv=sync are performed in parallel on 4.19 compared to 4.14. This bug was introduced during refactoring of blk-wbt code. Fixes: a79050434b45 ("blk-rq-qos: refactor out common elements of blk-wbt") Cc: stable@vger.kernel.org Cc: Josef Bacik Signed-off-by: Harshad Shirwadkar Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/blk-rq-qos.c | 14 +++++++++----- block/blk-rq-qos.h | 4 ++-- block/blk-wbt.c | 6 ++++-- 3 files changed, 15 insertions(+), 9 deletions(-) --- a/block/blk-rq-qos.c +++ b/block/blk-rq-qos.c @@ -148,24 +148,27 @@ bool rq_depth_calc_max_depth(struct rq_d return ret; } -void rq_depth_scale_up(struct rq_depth *rqd) +/* Returns true on success and false if scaling up wasn't possible */ +bool rq_depth_scale_up(struct rq_depth *rqd) { /* * Hit max in previous round, stop here */ if (rqd->scaled_max) - return; + return false; rqd->scale_step--; rqd->scaled_max = rq_depth_calc_max_depth(rqd); + return true; } /* * Scale rwb down. If 'hard_throttle' is set, do it quicker, since we - * had a latency violation. + * had a latency violation. Returns true on success and returns false if + * scaling down wasn't possible. */ -void rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle) +bool rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle) { /* * Stop scaling down when we've hit the limit. This also prevents @@ -173,7 +176,7 @@ void rq_depth_scale_down(struct rq_depth * keep up. */ if (rqd->max_depth == 1) - return; + return false; if (rqd->scale_step < 0 && hard_throttle) rqd->scale_step = 0; @@ -182,6 +185,7 @@ void rq_depth_scale_down(struct rq_depth rqd->scaled_max = false; rq_depth_calc_max_depth(rqd); + return true; } void rq_qos_exit(struct request_queue *q) --- a/block/blk-rq-qos.h +++ b/block/blk-rq-qos.h @@ -94,8 +94,8 @@ static inline void rq_qos_del(struct req } bool rq_wait_inc_below(struct rq_wait *rq_wait, unsigned int limit); -void rq_depth_scale_up(struct rq_depth *rqd); -void rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle); +bool rq_depth_scale_up(struct rq_depth *rqd); +bool rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle); bool rq_depth_calc_max_depth(struct rq_depth *rqd); void rq_qos_cleanup(struct request_queue *, struct bio *); --- a/block/blk-wbt.c +++ b/block/blk-wbt.c @@ -307,7 +307,8 @@ static void calc_wb_limits(struct rq_wb static void scale_up(struct rq_wb *rwb) { - rq_depth_scale_up(&rwb->rq_depth); + if (!rq_depth_scale_up(&rwb->rq_depth)) + return; calc_wb_limits(rwb); rwb->unknown_cnt = 0; rwb_wake_all(rwb); @@ -316,7 +317,8 @@ static void scale_up(struct rq_wb *rwb) static void scale_down(struct rq_wb *rwb, bool hard_throttle) { - rq_depth_scale_down(&rwb->rq_depth, hard_throttle); + if (!rq_depth_scale_down(&rwb->rq_depth, hard_throttle)) + return; calc_wb_limits(rwb); rwb->unknown_cnt = 0; rwb_trace_step(rwb, "scale down");