Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933636AbZLFKpR (ORCPT ); Sun, 6 Dec 2009 05:45:17 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933271AbZLFKpN (ORCPT ); Sun, 6 Dec 2009 05:45:13 -0500 Received: from mail-yx0-f188.google.com ([209.85.210.188]:63181 "EHLO mail-yx0-f188.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933262AbZLFKpL convert rfc822-to-8bit (ORCPT ); Sun, 6 Dec 2009 05:45:11 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type:content-transfer-encoding; b=dbLRjRlyQxlsFp61WtvArEgwpSHbtIAsg+ZLWcW/ipq0BqJz7ZMJKqtIep9lJxgpDN 2pw0BXdGKdnFhPEi2dKmYVs1XxdKghrQ4j7Pwj+74K8h3BbbWiQ0aBqCopx9Y0LO19Ny vZFlp/Ko3QTwhWHwKajFsaHo057FLfN57H8QE= MIME-Version: 1.0 In-Reply-To: <4e5e476b0912050313k280caa8bjf7c2cf1c5d19c88c@mail.gmail.com> References: <4b1a3d84.0d0db80a.39d0.ffff814a@mx.google.com> <4e5e476b0912050313k280caa8bjf7c2cf1c5d19c88c@mail.gmail.com> Date: Sun, 6 Dec 2009 11:45:16 +0100 Message-ID: <4e5e476b0912060245x4d64300hb9689243bd712f2c@mail.gmail.com> Subject: Re: [PATCH] cfq-iosched: reduce write depth only if sync was delayed From: Corrado Zoccolo To: Linux-Kernel , Jens Axboe , Jeff Moyer , Vivek Goyal Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3631 Lines: 95 Hi Jeff, I remember you saw large performance drop on your SAN for sequential writes with low_latency=1. Can you test if Shaohua's and this patch fix allow to recover some bandwidth? I think that enabling the queue depth ramp up only if a sync request was delayed should disable it for fast hardware like yours, so you should not be seeing the slowdown any more. Thanks, Corrado On Sat, Dec 5, 2009 at 12:13 PM, Corrado Zoccolo wrote: > On Fri, Dec 4, 2009 at 1:35 PM, Corrado Zoccolo wrote: >> The introduction of ramp-up formula for async queue depths has >> slowed down dirty page reclaim, by reducing async write performance. >> This patch makes sure the formula kicks in only when sync request >> was recently delayed. >> >> Signed-off-by: Corrado Zoccolo >> --- >>  block/cfq-iosched.c |    9 +++++---- >>  1 files changed, 5 insertions(+), 4 deletions(-) >> >> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c >> index b00ca4c..a594388 100644 >> --- a/block/cfq-iosched.c >> +++ b/block/cfq-iosched.c >> @@ -284,7 +284,7 @@ struct cfq_data { >>         */ >>        struct cfq_queue oom_cfqq; >> >> -       unsigned long last_end_sync_rq; >> +       unsigned long last_delayed_sync; >> >>        /* List of cfq groups being managed on this device*/ >>        struct hlist_head cfqg_list; >> @@ -2264,7 +2264,7 @@ static bool cfq_may_dispatch(struct cfq_data *cfqd, >> struct cfq_queue *cfqq) >>         * based on the last sync IO we serviced >>         */ >>        if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) { >> -               unsigned long last_sync = jiffies - cfqd->last_end_sync_rq; >> +               unsigned long last_sync = jiffies - cfqd->last_delayed_sync; >>                unsigned int depth; >> >>                depth = last_sync / cfqd->cfq_slice[1]; >> @@ -3272,7 +3272,8 @@ static void cfq_completed_request(struct request_queue >> *q, struct request *rq) >> >>        if (sync) { >>                RQ_CIC(rq)->last_end_request = now; >> -               cfqd->last_end_sync_rq = now; >> +               if (time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now)) >> +                       cfqd->last_delayed_sync = now; > > Sorry, the check be reversed (!time_after). > >>        } >> >>        /* >> @@ -3706,7 +3707,7 @@ static void *cfq_init_queue(struct request_queue *q) >>        cfqd->cfq_latency = 1; >>        cfqd->cfq_group_isolation = 0; >>        cfqd->hw_tag = -1; >> -       cfqd->last_end_sync_rq = jiffies; >> +       cfqd->last_delayed_sync = jiffies - HZ; >>        return cfqd; >>  } >> >> -- >> 1.6.2.5 >> >> >> >> > -- __________________________________________________________________________ dott. Corrado Zoccolo mailto:czoccolo@gmail.com PhD - Department of Computer Science - University of Pisa, Italy -------------------------------------------------------------------------- The self-confidence of a warrior is not the self-confidence of the average man. The average man seeks certainty in the eyes of the onlooker and calls that self-confidence. The warrior seeks impeccability in his own eyes and calls that humbleness. Tales of Power - C. Castaneda -- 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/