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cfq-iosched: Implement tunable group_idle
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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 <[email protected]>
Acked-by: Jeff Moyer <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
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@rhvgoyal
rhvgoyal authored and Jens Axboe committed Aug 23, 2010
1 parent 02b3508 commit 80bdf0c
Showing 1 changed file with 56 additions and 9 deletions.
65 changes: 56 additions & 9 deletions block/cfq-iosched.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;

Expand Down Expand Up @@ -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;
};

/*
Expand Down Expand Up @@ -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;

Expand Down Expand Up @@ -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
Expand All @@ -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
Expand All @@ -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);
}

/*
Expand All @@ -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)]++;
Expand Down Expand Up @@ -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;
}

/*
Expand Down Expand Up @@ -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;
}
Expand Down Expand Up @@ -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));
Expand Down Expand Up @@ -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");
}
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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,
Expand All @@ -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
Expand Down Expand Up @@ -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;

Expand Down

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