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-rw-r--r--block/cfq-iosched.c53
1 files changed, 51 insertions, 2 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 418da9a49bb..97d946585bc 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -27,6 +27,8 @@ 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 const int cfq_target_latency = HZ * 3/10; /* 300 ms */
+static const int cfq_hist_divisor = 4;
/*
* offset from end of service tree
@@ -148,6 +150,8 @@ struct cfq_data {
struct rb_root prio_trees[CFQ_PRIO_LISTS];
unsigned int busy_queues;
+ unsigned int busy_rt_queues;
+ unsigned int busy_queues_avg[2];
int rq_in_driver[2];
int sync_flight;
@@ -315,10 +319,52 @@ cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
}
+/*
+ * get averaged number of queues of RT/BE priority.
+ * average is updated, with a formula that gives more weight to higher numbers,
+ * to quickly follows sudden increases and decrease slowly
+ */
+
+static inline unsigned
+cfq_get_avg_queues(struct cfq_data *cfqd, bool rt) {
+ unsigned min_q, max_q;
+ unsigned mult = cfq_hist_divisor - 1;
+ unsigned round = cfq_hist_divisor / 2;
+ unsigned busy = cfqd->busy_rt_queues;
+
+ if (!rt)
+ busy = cfqd->busy_queues - cfqd->busy_rt_queues;
+
+ min_q = min(cfqd->busy_queues_avg[rt], busy);
+ max_q = max(cfqd->busy_queues_avg[rt], busy);
+ cfqd->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
+ cfq_hist_divisor;
+ return cfqd->busy_queues_avg[rt];
+}
+
static inline void
cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
- cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
+ unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
+ if (cfqd->cfq_latency) {
+ /* interested queues (we consider only the ones with the same
+ * priority class) */
+ unsigned iq = cfq_get_avg_queues(cfqd, cfq_class_rt(cfqq));
+ unsigned sync_slice = cfqd->cfq_slice[1];
+ unsigned expect_latency = sync_slice * iq;
+ if (expect_latency > cfq_target_latency) {
+ unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
+ /* scale low_slice according to IO priority
+ * and sync vs async */
+ unsigned low_slice =
+ min(slice, base_low_slice * slice / sync_slice);
+ /* the adapted slice value is scaled to fit all iqs
+ * into the target latency */
+ slice = max(slice * cfq_target_latency / expect_latency,
+ low_slice);
+ }
+ }
+ cfqq->slice_end = jiffies + slice;
cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
}
@@ -669,7 +715,8 @@ static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
BUG_ON(cfq_cfqq_on_rr(cfqq));
cfq_mark_cfqq_on_rr(cfqq);
cfqd->busy_queues++;
-
+ if (cfq_class_rt(cfqq))
+ cfqd->busy_rt_queues++;
cfq_resort_rr_list(cfqd, cfqq);
}
@@ -692,6 +739,8 @@ static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
BUG_ON(!cfqd->busy_queues);
cfqd->busy_queues--;
+ if (cfq_class_rt(cfqq))
+ cfqd->busy_rt_queues--;
}
/*