Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753169Ab3JSPfy (ORCPT ); Sat, 19 Oct 2013 11:35:54 -0400 Received: from merlin.infradead.org ([205.233.59.134]:39384 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751258Ab3JSPfx (ORCPT ); Sat, 19 Oct 2013 11:35:53 -0400 Date: Sat, 19 Oct 2013 17:35:35 +0200 From: Peter Zijlstra To: Frederic Weisbecker 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: <20131019153535.GA2490@laptop.programming.kicks-ass.net> References: <1382195841-6558-1-git-send-email-fweisbec@gmail.com> <1382195841-6558-5-git-send-email-fweisbec@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1382195841-6558-5-git-send-email-fweisbec@gmail.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1538 Lines: 51 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 ;-) I just had a look at delayacct; wth wrote that crap; that too uses gtod. -- 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/