Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966344Ab0GSS6z (ORCPT ); Mon, 19 Jul 2010 14:58:55 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41913 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965095Ab0GSS6w (ORCPT ); Mon, 19 Jul 2010 14:58:52 -0400 From: Jeff Moyer To: Vivek Goyal Cc: linux-kernel@vger.kernel.org, axboe@kernel.dk, nauman@google.com, dpshah@google.com, guijianfeng@cn.fujitsu.com, czoccolo@gmail.com Subject: Re: [PATCH 2/3] cfq-iosched: Implement a new tunable group_idle References: <1279560008-2905-1-git-send-email-vgoyal@redhat.com> <1279560008-2905-3-git-send-email-vgoyal@redhat.com> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? Date: Mon, 19 Jul 2010 14:58:41 -0400 In-Reply-To: <1279560008-2905-3-git-send-email-vgoyal@redhat.com> (Vivek Goyal's message of "Mon, 19 Jul 2010 13:20:07 -0400") Message-ID: User-Agent: Gnus/5.110011 (No Gnus v0.11) Emacs/23.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4087 Lines: 120 Vivek Goyal writes: > o Implement a new tunable group_idle, which allows idling on the group > instead of a cfq queue. Hence one can set slice_idle = 0 and not idle > on the individual queues but idle on the group. This way on fast storage > we can get fairness between groups at the same time overall throughput > improves. > > Signed-off-by: Vivek Goyal > --- > block/cfq-iosched.c | 60 +++++++++++++++++++++++++++++++++++++++++++++------ > 1 files changed, 53 insertions(+), 7 deletions(-) > > diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c > index f44064c..b23d7f4 100644 > --- a/block/cfq-iosched.c > +++ b/block/cfq-iosched.c > @@ -30,6 +30,7 @@ static const int cfq_slice_sync = HZ / 10; > static int cfq_slice_async = HZ / 25; > static const int cfq_slice_async_rq = 2; > static int cfq_slice_idle = HZ / 125; > +static int cfq_group_idle = HZ / 125; > static const int cfq_target_latency = HZ * 3/10; /* 300 ms */ > static const int cfq_hist_divisor = 4; > > @@ -198,6 +199,8 @@ struct cfq_group { > struct hlist_node cfqd_node; > atomic_t ref; > #endif > + /* number of requests that are on the dispatch list or inside driver */ > + int dispatched; > }; > > /* > @@ -271,6 +274,7 @@ struct cfq_data { > unsigned int cfq_slice[2]; > unsigned int cfq_slice_async_rq; > unsigned int cfq_slice_idle; > + unsigned int cfq_group_idle; > unsigned int cfq_latency; > unsigned int cfq_group_isolation; > > @@ -1856,6 +1860,9 @@ static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq) > BUG_ON(!service_tree); > BUG_ON(!service_tree->count); > > + if (!cfqd->cfq_slice_idle) > + return false; > + > /* We never do for idle class queues. */ > if (prio == IDLE_WORKLOAD) > return false; > @@ -1880,7 +1887,7 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd) > { > struct cfq_queue *cfqq = cfqd->active_queue; > struct cfq_io_context *cic; > - unsigned long sl; > + unsigned long sl, group_idle = 0; > > /* > * SSD device without seek penalty, disable idling. But only do so > @@ -1896,8 +1903,13 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd) > /* > * idle is disabled, either manually or by past process history > */ > - if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq)) > - return; > + if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq)) { The check for cfqd->cfq_slice_idle is now redundant (as it's done in cfq_should_idle). > @@ -2215,7 +2236,7 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd) > cfqq = NULL; > goto keep_queue; > } else > - goto expire; > + goto check_group_idle; > } > > /* > @@ -2249,6 +2270,17 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd) > goto keep_queue; > } > > + /* > + * If group idle is enabled and there are requests dispatched from > + * this group, wait for requests to complete. > + */ > +check_group_idle: > + if (cfqd->cfq_group_idle && cfqq->cfqg->nr_cfqq == 1 > + && cfqq->cfqg->dispatched) { > + cfqq = NULL; > + goto keep_queue; > + } I really wish we could roll all of this logic into cfq_should_idle. > @@ -3420,7 +3453,10 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq) > * the queue. > */ > if (cfq_should_wait_busy(cfqd, cfqq)) { > - cfqq->slice_end = jiffies + cfqd->cfq_slice_idle; > + unsigned long extend_sl = cfqd->cfq_slice_idle; > + if (!cfqd->cfq_slice_idle) > + extend_sl = cfqd->cfq_group_idle; > + cfqq->slice_end = jiffies + extend_sl; So, if slice_idle and group_idle are both set, slice_idle trumps group_idle? Did you give that case any thought? If it doesn't make sense to configure both, then we should probably make sure they can't both be set. Cheers, Jeff -- 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/