From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752562AbaFECQh (ORCPT ); Wed, 4 Jun 2014 22:16:37 -0400 Received: from mail-pb0-f45.google.com ([209.85.160.45]:45911 "EHLO mail-pb0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751363AbaFECQg (ORCPT ); Wed, 4 Jun 2014 22:16:36 -0400 Message-ID: <538FD300.7010706@kernel.dk> Date: Wed, 04 Jun 2014 20:16:32 -0600 From: Jens Axboe User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Shaohua Li CC: =?ISO-8859-1?Q?Matias_Bj=F8rling?= , "Sam Bradshaw (sbradshaw)" , LKML Subject: Re: [PATCH] block: per-cpu counters for in-flight IO accounting References: <1399627061-5960-1-git-send-email-m@bjorling.me> <1399627061-5960-2-git-send-email-m@bjorling.me> <536CE25C.5040107@kernel.dk> <536D0537.7010905@kernel.dk> <20140530121119.GA1637@kernel.org> <53888C80.2020206@kernel.dk> <20140604103901.GA14383@kernel.org> <538F7CCE.3050508@kernel.dk> <20140605020934.GB13953@kernel.org> In-Reply-To: <20140605020934.GB13953@kernel.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2014-06-04 20:09, Shaohua Li wrote: > On Wed, Jun 04, 2014 at 02:08:46PM -0600, Jens Axboe wrote: >> On 06/04/2014 05:29 AM, Matias Bjørling wrote: >>> It's in >>> >>> blk_io_account_start >>> part_round_stats >>> part_round_state_single >>> part_in_flight >>> >>> I like the granularity idea. >> >> And similarly from blk_io_account_done() - which makes it even worse, >> since it at both ends of the IO chain. > > But part_round_state_single is supposed to only call part_in_flight every > jiffery. Maybe we need something below: > 1. set part->stamp immediately > 2. fixed granularity > Untested though. > > > diff --git a/block/blk-core.c b/block/blk-core.c > index 40d6548..5f0acaa 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -1270,17 +1270,19 @@ static void part_round_stats_single(int cpu, struct hd_struct *part, > unsigned long now) > { > int inflight; > + unsigned long old_stamp; > > - if (now == part->stamp) > + if (time_before(now, part->stamp + msecs_to_jiffies(10))) > return; > + old_stamp = part->stamp; > + part->stamp = now; > > inflight = part_in_flight(part); > if (inflight) { > __part_stat_add(cpu, part, time_in_queue, > - inflight * (now - part->stamp)); > - __part_stat_add(cpu, part, io_ticks, (now - part->stamp)); > + inflight * (now - old_stamp)); > + __part_stat_add(cpu, part, io_ticks, (now - old_stamp)); > } > - part->stamp = now; > } > > /** It'd be a good improvement, and one we should be able to do without screwing anything up. It'd be identical to anyone running at HZ==100 right now. So the above we can easily do, and arguably should just do. We wont see real scaling in the IO stats path before we fixup the hd_struct referencing as well, however. -- Jens Axboe