Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755341AbZGBUDR (ORCPT ); Thu, 2 Jul 2009 16:03:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754511AbZGBUDE (ORCPT ); Thu, 2 Jul 2009 16:03:04 -0400 Received: from mx2.redhat.com ([66.187.237.31]:52956 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754404AbZGBUDD (ORCPT ); Thu, 2 Jul 2009 16:03:03 -0400 From: Vivek Goyal To: linux-kernel@vger.kernel.org, containers@lists.linux-foundation.org, dm-devel@redhat.com, jens.axboe@oracle.com, nauman@google.com, dpshah@google.com, lizf@cn.fujitsu.com, mikew@google.com, fchecconi@gmail.com, paolo.valente@unimore.it, ryov@valinux.co.jp, fernando@oss.ntt.co.jp, s-uchida@ap.jp.nec.com, taka@valinux.co.jp, guijianfeng@cn.fujitsu.com, jmoyer@redhat.com, dhaval@linux.vnet.ibm.com, balbir@linux.vnet.ibm.com, righi.andrea@gmail.com, m-ikeda@ds.jp.nec.com, jbaron@redhat.com Cc: agk@redhat.com, snitzer@redhat.com, vgoyal@redhat.com, akpm@linux-foundation.org, peterz@infradead.org Subject: [PATCH 25/25] io-controller: experimental debug patch for async queue wait before expiry Date: Thu, 2 Jul 2009 16:01:57 -0400 Message-Id: <1246564917-19603-26-git-send-email-vgoyal@redhat.com> In-Reply-To: <1246564917-19603-1-git-send-email-vgoyal@redhat.com> References: <1246564917-19603-1-git-send-email-vgoyal@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7346 Lines: 182 o A debug patch which does wait for next IO from async queue once it becomes empty. o For async writes, traffic seen by IO scheduler is not in proportion to the weight of the cgroup task/page belongs to. So if there are two processes doing heavy writeouts in two cgroups with weights 1000 and 500 respectively, then IO scheduler does not see more traffic/IO from higher weight cgroup even if IO scheduler tries to give it higher disk time. Effectively, the async queue belonging to higher weight cgroup becomes empty, and gets out of contention for disk and lower weight cgroup gets to use disk giving an impression in user space that higher weight cgroup did not get higher time to disk. o This is more of a problem at page cache level where a higher weight process might be writing out the pages of lower weight process etc and should be fixed there. o While we fix those issues, introducing this debug patch which allows one to idle on async queue (tunable via /sys/blolc//queue/async_slice_idle) so that once a higher weight queue becomes empty, instead of expiring it we try to wait for next request to come from that queue hence giving it higher disk time. A higher value of async_slice_idle, around 300ms, helps me get some right numbers for my setup. Note: higher disk time would not necessarily translate in more IO done as higher weight group is not pushing enough IO to io scheduler. It is just a debugging aid to prove correctness of IO controller by providing higher disk times to higher weight cgroup. Signed-off-by: Vivek Goyal --- block/cfq-iosched.c | 1 + block/elevator-fq.c | 39 ++++++++++++++++++++++++++++++++++++--- block/elevator-fq.h | 5 +++++ 3 files changed, 42 insertions(+), 3 deletions(-) diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index a40a2fa..fbe56a9 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -2093,6 +2093,7 @@ static struct elv_fs_entry cfq_attrs[] = { ELV_ATTR(slice_sync), ELV_ATTR(slice_async), ELV_ATTR(fairness), + ELV_ATTR(async_slice_idle), __ATTR_NULL }; diff --git a/block/elevator-fq.c b/block/elevator-fq.c index 5b3f068..7c83d1e 100644 --- a/block/elevator-fq.c +++ b/block/elevator-fq.c @@ -24,6 +24,7 @@ const int elv_slice_sync = HZ / 10; int elv_slice_async = HZ / 25; const int elv_slice_async_rq = 2; int elv_slice_idle = HZ / 125; +int elv_async_slice_idle = 0; static struct kmem_cache *elv_ioq_pool; /* Maximum Window length for updating average disk rate */ @@ -2819,6 +2820,8 @@ SHOW_FUNCTION(elv_slice_async_show, efqd->elv_slice[0], 1); EXPORT_SYMBOL(elv_slice_async_show); SHOW_FUNCTION(elv_fairness_show, efqd->fairness, 0); EXPORT_SYMBOL(elv_fairness_show); +SHOW_FUNCTION(elv_async_slice_idle_show, efqd->elv_async_slice_idle, 1); +EXPORT_SYMBOL(elv_async_slice_idle_show); #undef SHOW_FUNCTION #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ @@ -2845,6 +2848,8 @@ STORE_FUNCTION(elv_slice_async_store, &efqd->elv_slice[0], 1, UINT_MAX, 1); EXPORT_SYMBOL(elv_slice_async_store); STORE_FUNCTION(elv_fairness_store, &efqd->fairness, 0, 2, 0); EXPORT_SYMBOL(elv_fairness_store); +STORE_FUNCTION(elv_async_slice_idle_store, &efqd->elv_async_slice_idle, 0, UINT_MAX, 1); +EXPORT_SYMBOL(elv_async_slice_idle_store); #undef STORE_FUNCTION void elv_schedule_dispatch(struct request_queue *q) @@ -3018,7 +3023,7 @@ int elv_init_ioq(struct elevator_queue *eq, struct io_queue *ioq, ioq->pid = current->pid; ioq->sched_queue = sched_queue; - if (is_sync && !elv_ioq_class_idle(ioq)) + if (!elv_ioq_class_idle(ioq) && (is_sync || efqd->fairness)) elv_mark_ioq_idle_window(ioq); bfq_init_entity(&ioq->entity, iog); ioq->entity.budget = elv_prio_to_slice(efqd, ioq); @@ -3699,7 +3704,12 @@ static void elv_ioq_arm_slice_timer(struct request_queue *q, int wait_for_busy) /* * idle is disabled, either manually or by past process history */ - if (!efqd->elv_slice_idle || !elv_ioq_idle_window(ioq)) + if ((elv_ioq_sync(ioq) && !efqd->elv_slice_idle) || + !elv_ioq_idle_window(ioq)) + return; + + /* If this is async queue and async_slice_idle is disabled, return */ + if (!elv_ioq_sync(ioq) && !efqd->elv_async_slice_idle) return; /* @@ -3708,7 +3718,10 @@ static void elv_ioq_arm_slice_timer(struct request_queue *q, int wait_for_busy) */ if (wait_for_busy) { elv_mark_ioq_wait_busy(ioq); - sl = efqd->elv_slice_idle; + if (elv_ioq_sync(ioq)) + sl = efqd->elv_slice_idle; + else + sl = efqd->elv_async_slice_idle; mod_timer(&efqd->idle_slice_timer, jiffies + sl); elv_log_ioq(efqd, ioq, "arm idle: %lu wait busy=1", sl); return; @@ -3882,6 +3895,18 @@ void *elv_fq_select_ioq(struct request_queue *q, int force) goto keep_queue; } + /* + * If this is an async queue which has time slice left but not + * requests. Wait busy is also not on (may be because when last + * request completed, ioq was not empty). Wait for the request + * completion. May be completion will turn wait busy on. + */ + if (efqd->fairness && efqd->elv_async_slice_idle && !elv_ioq_sync(ioq) + && elv_ioq_nr_dispatched(ioq)) { + ioq = NULL; + goto keep_queue; + } + slice_expired = 0; expire: if (efqd->fairness >= 2 && !force && ioq && ioq->dispatched @@ -4076,6 +4101,13 @@ void elv_ioq_completed_request(struct request_queue *q, struct request *rq) goto done; } + /* For async queue try to do wait busy */ + if (efqd->fairness && !elv_ioq_sync(ioq) && !ioq->nr_queued + && (elv_iog_nr_active(iog) <= 1)) { + elv_ioq_arm_slice_timer(q, 1); + goto done; + } + /* * If there are no requests waiting in this queue, and * there are other queues ready to issue requests, AND @@ -4215,6 +4247,7 @@ int elv_init_fq_data(struct request_queue *q, struct elevator_queue *e) efqd->elv_slice[0] = elv_slice_async; efqd->elv_slice[1] = elv_slice_sync; efqd->elv_slice_idle = elv_slice_idle; + efqd->elv_async_slice_idle = elv_async_slice_idle; efqd->hw_tag = 1; /* For the time being keep fairness enabled by default */ diff --git a/block/elevator-fq.h b/block/elevator-fq.h index 19ac8ca..f089a55 100644 --- a/block/elevator-fq.h +++ b/block/elevator-fq.h @@ -362,6 +362,8 @@ struct elv_fq_data { * users of this functionality. */ unsigned int elv_slice_idle; + /* idle slice for async queue */ + unsigned int elv_async_slice_idle; struct timer_list idle_slice_timer; struct work_struct unplug_work; @@ -647,6 +649,9 @@ extern ssize_t elv_slice_async_store(struct elevator_queue *q, const char *name, extern ssize_t elv_fairness_show(struct elevator_queue *q, char *name); extern ssize_t elv_fairness_store(struct elevator_queue *q, const char *name, size_t count); +extern ssize_t elv_async_slice_idle_show(struct elevator_queue *q, char *name); +extern ssize_t elv_async_slice_idle_store(struct elevator_queue *q, + const char *name, size_t count); /* Functions used by elevator.c */ extern int elv_init_fq_data(struct request_queue *q, struct elevator_queue *e); -- 1.6.0.6 -- 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/