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 E194BFA3728 for ; Wed, 16 Oct 2019 22:00:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B6D2E20872 for ; Wed, 16 Oct 2019 22:00:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571263218; bh=U5szriT2EOgaFeUPKZQdL0lipD5B8CBqq2qiB1askLE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=19k9CLhbw6TtQl1lhcoyZRRdtbD0gNh7G5kJ3T7jMFMSLq/+8ins8cNlxNX9M3h9S 9HOra//eElxZsYOc2Np0jU2iYM5hoU9jmzBV15+t1xmsM50tXxF7Hzwsm56zFdcAZD idhkli/DZbXMmaev5dLhIyffwfNh5mQ+Jw1v+MdE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2406763AbfJPWAS (ORCPT ); Wed, 16 Oct 2019 18:00:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:53566 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2438411AbfJPV7K (ORCPT ); Wed, 16 Oct 2019 17:59:10 -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 A557D21A4C; Wed, 16 Oct 2019 21:59:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571263149; bh=U5szriT2EOgaFeUPKZQdL0lipD5B8CBqq2qiB1askLE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SRPFKlUrMwawLfPTpI1FC/Z+ppx5PpbhZXSe3yks4AYOwKKEmA/9muUJbr6vAvGmM TikHJhqOn9xvqnhX59kStdxKAwnr5KL+QpJAzZSm+1ohZZ+maASsC0N2SUa5chzuKc jXvvZV+FpFLsosQT8dOcVvJFgsAPWNduacQUaI7k= 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 5.3 069/112] blk-wbt: fix performance regression in wbt scale_up/scale_down Date: Wed, 16 Oct 2019 14:51:01 -0700 Message-Id: <20191016214903.060443070@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191016214844.038848564@linuxfoundation.org> References: <20191016214844.038848564@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 @@ -142,24 +142,27 @@ 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 @@ -167,7 +170,7 @@ 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; @@ -176,6 +179,7 @@ void rq_depth_scale_down(struct rq_depth rqd->scaled_max = false; rq_depth_calc_max_depth(rqd); + return true; } struct rq_qos_wait_data { --- a/block/blk-rq-qos.h +++ b/block/blk-rq-qos.h @@ -125,8 +125,8 @@ void rq_qos_wait(struct rq_wait *rqw, vo acquire_inflight_cb_t *acquire_inflight_cb, cleanup_cb_t *cleanup_cb); 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 rq_qos *rqos, struct bio *bio); --- a/block/blk-wbt.c +++ b/block/blk-wbt.c @@ -308,7 +308,8 @@ 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); @@ -317,7 +318,8 @@ 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");