diff options
| -rw-r--r-- | block/cfq-iosched.c | 30 |
1 files changed, 26 insertions, 4 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index f27e535ce262..0db07d7771b5 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -19,7 +19,7 @@ * tunables */ /* max queue in one round of service */ -static const int cfq_quantum = 4; +static const int cfq_quantum = 8; static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 }; /* maximum backwards seek, in KiB */ static const int cfq_back_max = 16 * 1024; @@ -2197,6 +2197,19 @@ static int cfq_forced_dispatch(struct cfq_data *cfqd) return dispatched; } +static inline bool cfq_slice_used_soon(struct cfq_data *cfqd, + struct cfq_queue *cfqq) +{ + /* the queue hasn't finished any request, can't estimate */ + if (cfq_cfqq_slice_new(cfqq)) + return 1; + if (time_after(jiffies + cfqd->cfq_slice_idle * cfqq->dispatched, + cfqq->slice_end)) + return 1; + + return 0; +} + static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq) { unsigned int max_dispatch; @@ -2213,7 +2226,7 @@ static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq) if (cfqd->rq_in_flight[BLK_RW_SYNC] && !cfq_cfqq_sync(cfqq)) return false; - max_dispatch = cfqd->cfq_quantum; + max_dispatch = max_t(unsigned int, cfqd->cfq_quantum / 2, 1); if (cfq_class_idle(cfqq)) max_dispatch = 1; @@ -2230,13 +2243,22 @@ static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq) /* * We have other queues, don't allow more IO from this one */ - if (cfqd->busy_queues > 1) + if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq)) return false; /* * Sole queue user, no limit */ - max_dispatch = -1; + if (cfqd->busy_queues == 1) + max_dispatch = -1; + else + /* + * Normally we start throttling cfqq when cfq_quantum/2 + * requests have been dispatched. But we can drive + * deeper queue depths at the beginning of slice + * subjected to upper limit of cfq_quantum. + * */ + max_dispatch = cfqd->cfq_quantum; } /* |