From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758000AbcKCPdu (ORCPT ); Thu, 3 Nov 2016 11:33:50 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:56284 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753398AbcKCPds (ORCPT ); Thu, 3 Nov 2016 11:33:48 -0400 DMARC-Filter: OpenDMARC Filter v1.3.1 smtp.codeaurora.org BD534615BA Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=pass smtp.mailfrom=pkondeti@codeaurora.org MIME-Version: 1.0 In-Reply-To: <1477673892-28940-2-git-send-email-tj@kernel.org> References: <1477673892-28940-1-git-send-email-tj@kernel.org> <1477673892-28940-2-git-send-email-tj@kernel.org> From: Pavan Kondeti Date: Thu, 3 Nov 2016 21:03:45 +0530 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 1/4] sched: move IO scheduling accounting from io_schedule_timeout() to __schedule() To: Tejun Heo Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, mingo@redhat.com, Peter Zijlstra , axboe@kernel.dk, tytso@mit.edu, jack@suse.com, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, mingbo@fb.com Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Tejun, > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 94732d1..f6baa38 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -3336,11 +3336,17 @@ static void __sched notrace __schedule(bool preempt) > unsigned long *switch_count; > struct pin_cookie cookie; > struct rq *rq; > - int cpu; > + int cpu, in_iowait; > > cpu = smp_processor_id(); > rq = cpu_rq(cpu); > prev = rq->curr; > + in_iowait = prev->in_iowait; > + > + if (in_iowait) { > + delayacct_blkio_start(); > + atomic_inc(&rq->nr_iowait); > + } > > schedule_debug(prev); > > @@ -3406,6 +3412,11 @@ static void __sched notrace __schedule(bool preempt) > } > > balance_callback(rq); > + > + if (in_iowait) { > + atomic_dec(&rq->nr_iowait); > + delayacct_blkio_end(); > + } > } I think, the nr_iowait update can go wrong here. When the task migrates to a different CPU upon wakeup, this rq points to a different CPU from the one on which nr_iowait is incremented before. Thanks, Pavan -- Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project