Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751801Ab3JSQCm (ORCPT ); Sat, 19 Oct 2013 12:02:42 -0400 Received: from mail-wi0-f177.google.com ([209.85.212.177]:60234 "EHLO mail-wi0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751290Ab3JSQCl (ORCPT ); Sat, 19 Oct 2013 12:02:41 -0400 Date: Sat, 19 Oct 2013 18:02:37 +0200 From: Frederic Weisbecker To: Peter Zijlstra Cc: Oleg Nesterov , LKML , Fernando Luis Vazquez Cao , Tetsuo Handa , Thomas Gleixner , Ingo Molnar , Andrew Morton , Arjan van de Ven Subject: Re: [PATCH 4/5] sched: Refactor iowait accounting Message-ID: <20131019160235.GA13534@localhost.localdomain> References: <1382195841-6558-1-git-send-email-fweisbec@gmail.com> <1382195841-6558-5-git-send-email-fweisbec@gmail.com> <20131019153535.GA2490@laptop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131019153535.GA2490@laptop.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1865 Lines: 57 On Sat, Oct 19, 2013 at 05:35:35PM +0200, Peter Zijlstra wrote: > On Sat, Oct 19, 2013 at 05:17:20PM +0200, Frederic Weisbecker wrote: > > +u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time) > > +{ > > + ktime_t iowait, delta = { .tv64 = 0 }; > > + struct rq *rq = cpu_rq(cpu); > > + ktime_t now = ktime_get(); > > + unsigned int seq; > > + > > + do { > > + seq = read_seqbegin(&rq->iowait_lock); > > + if (rq->nr_iowait) > > + delta = ktime_sub(now, rq->iowait_start); > > + iowait = ktime_add(rq->iowait_time, delta); > > + } while (read_seqretry(&rq->iowait_lock, seq)); > > + > > + if (last_update_time) > > + *last_update_time = ktime_to_us(now); > > + > > + return ktime_to_us(iowait); > > +} > > +EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us); > > + > > +static void cpu_iowait_start(struct rq *rq) > > +{ > > + write_seqlock(&rq->iowait_lock); > > + if (!rq->nr_iowait++) > > + rq->iowait_start = ktime_get(); > > + write_sequnlock(&rq->iowait_lock); > > +} > > + > > +static void cpu_iowait_end(struct rq *rq) > > +{ > > + ktime_t delta; > > + write_seqlock(&rq->iowait_lock); > > + if (!--rq->nr_iowait) { > > + delta = ktime_sub(ktime_get(), rq->iowait_start); > > + rq->iowait_time = ktime_add(rq->iowait_time, delta); > > + } > > + write_sequnlock(&rq->iowait_lock); > > +} > > Yeah, so using ktime_get() for this is completely insane ;-) Woops, yeah I clearly overlooked that while moving the code :) local_clock() should be fine. > > I just had a look at delayacct; wth wrote that crap; that too uses > gtod. I can't find where it does that. kernel/delayacct.c doesn't seem to at least. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/