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Message-ID: <x498w46fkyy.fsf@segfault.boston.devel.redhat.com>
Date: Mon, 16 Aug 2010 14:53:09 -0400
From: Jeff Moyer <jmoyer@...hat.com>
To: Vivek Goyal <vgoyal@...hat.com>
Cc: linux-kernel@...r.kernel.org, jaxboe@...ionio.com
Subject: Re: [PATCH 3/5] cfq-iosched: Implement tunable group_idle
Vivek Goyal <vgoyal@...hat.com> 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 <vgoyal@...hat.com>
Reviewed-by: Jeff Moyer <jmoyer@...hat.com>
> ---
> block/cfq-iosched.c | 65 +++++++++++++++++++++++++++++++++++++++++++-------
> 1 files changed, 56 insertions(+), 9 deletions(-)
>
> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
> index 3fc6be1..85e4819 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;
>
> @@ -1884,7 +1888,7 @@ 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
> @@ -1900,8 +1904,13 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
> /*
> * idle is disabled, either manually or by past process history
> */
> - if (!cfq_should_idle(cfqd, cfqq))
> - return;
> + if (!cfq_should_idle(cfqd, cfqq)) {
> + /* no queue idling. Check for group idling */
> + if (cfqd->cfq_group_idle)
> + group_idle = cfqd->cfq_group_idle;
> + else
> + return;
> + }
>
> /*
> * still active requests from this queue, don't idle
> @@ -1928,13 +1937,21 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
> return;
> }
>
> + /* There are other queues in the group, don't do group idle */
> + if (group_idle && cfqq->cfqg->nr_cfqq > 1)
> + return;
> +
> cfq_mark_cfqq_wait_request(cfqq);
>
> - sl = cfqd->cfq_slice_idle;
> + if (group_idle)
> + sl = cfqd->cfq_group_idle;
> + else
> + sl = cfqd->cfq_slice_idle;
>
> mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
> cfq_blkiocg_update_set_idle_time_stats(&cfqq->cfqg->blkg);
> - cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);
> + cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu group_idle: %d", sl,
> + group_idle ? 1 : 0);
> }
>
> /*
> @@ -1950,6 +1967,7 @@ static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
> cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
> cfq_remove_request(rq);
> cfqq->dispatched++;
> + (RQ_CFQG(rq))->dispatched++;
> elv_dispatch_sort(q, rq);
>
> cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
> @@ -2219,7 +2237,7 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
> cfqq = NULL;
> goto keep_queue;
> } else
> - goto expire;
> + goto check_group_idle;
> }
>
> /*
> @@ -2247,8 +2265,23 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
> * flight or is idling for a new request, allow either of these
> * conditions to happen (or time out) before selecting a new queue.
> */
> - if (timer_pending(&cfqd->idle_slice_timer) ||
> - (cfqq->dispatched && cfq_should_idle(cfqd, cfqq))) {
> + if (timer_pending(&cfqd->idle_slice_timer)) {
> + cfqq = NULL;
> + goto keep_queue;
> + }
> +
> + if (cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
> + cfqq = NULL;
> + 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;
> }
> @@ -3396,6 +3429,7 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
> WARN_ON(!cfqq->dispatched);
> cfqd->rq_in_driver--;
> cfqq->dispatched--;
> + (RQ_CFQG(rq))->dispatched--;
> cfq_blkiocg_update_completion_stats(&cfqq->cfqg->blkg,
> rq_start_time_ns(rq), rq_io_start_time_ns(rq),
> rq_data_dir(rq), rq_is_sync(rq));
> @@ -3425,7 +3459,10 @@ 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;
> cfq_mark_cfqq_wait_busy(cfqq);
> cfq_log_cfqq(cfqd, cfqq, "will busy wait");
> }
> @@ -3871,6 +3908,7 @@ static void *cfq_init_queue(struct request_queue *q)
> cfqd->cfq_slice[1] = cfq_slice_sync;
> cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
> cfqd->cfq_slice_idle = cfq_slice_idle;
> + cfqd->cfq_group_idle = cfq_group_idle;
> cfqd->cfq_latency = 1;
> cfqd->cfq_group_isolation = 0;
> cfqd->hw_tag = -1;
> @@ -3943,6 +3981,7 @@ SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
> SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
> SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
> SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
> +SHOW_FUNCTION(cfq_group_idle_show, cfqd->cfq_group_idle, 1);
> SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
> SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
> SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
> @@ -3975,6 +4014,7 @@ STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
> STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
> UINT_MAX, 0);
> STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
> +STORE_FUNCTION(cfq_group_idle_store, &cfqd->cfq_group_idle, 0, UINT_MAX, 1);
> STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
> STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
> STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
> @@ -3996,6 +4036,7 @@ static struct elv_fs_entry cfq_attrs[] = {
> CFQ_ATTR(slice_async),
> CFQ_ATTR(slice_async_rq),
> CFQ_ATTR(slice_idle),
> + CFQ_ATTR(group_idle),
> CFQ_ATTR(low_latency),
> CFQ_ATTR(group_isolation),
> __ATTR_NULL
> @@ -4049,6 +4090,12 @@ static int __init cfq_init(void)
> if (!cfq_slice_idle)
> cfq_slice_idle = 1;
>
> +#ifdef CONFIG_CFQ_GROUP_IOSCHED
> + if (!cfq_group_idle)
> + cfq_group_idle = 1;
> +#else
> + cfq_group_idle = 0;
> +#endif
> if (cfq_slab_setup())
> return -ENOMEM;
--
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