cfq-iosched: Implement group idle V2

index 7982b83..f44064c 100644
@@ -896,16 +896,34 @@ static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)
 		 * if there are mutiple queues in the group, each can dispatch
 		 * a single request on seeky media and cause lots of seek time
 		 * and group will never know it.
+		 *
+		 * If drive is NCQ and we are driving deep queue depths, then
+		 * it is not reasonable to charge the slice since dispatch
+		 * started because this time will include time taken by all
+		 * the other requests in the queue.
+		 *
+		 * Actually there is no reasonable way to know the disk time
+		 * here and we need to come up with some approximation. If
+		 * disk is non NCQ, we should be driving request queue depth
+		 * 1, then charge for time since dispatch start and this will
+		 * account for seek time properly on seeky media. If request
+		 * queue depth is high, then charge for number of requests
+		 * dispatched from the queue. This will sort of becoming
+		 * charging in terms of IOPS.
 		 */
-		slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
-					1);
+		if (cfqq->cfqd->hw_tag == 0)
+			slice_used = max_t(unsigned,
+					(jiffies - cfqq->dispatch_start), 1);
+		else
+			slice_used = cfqq->slice_dispatch;
 	} else {
 		slice_used = jiffies - cfqq->slice_start;
 		if (slice_used > cfqq->allocated_slice)
 			slice_used = cfqq->allocated_slice;
 	}
 
-	cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u", slice_used);
+	cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u, sl_disp=%u", slice_used,
+			cfqq->slice_dispatch);
 	return slice_used;
 }
 

index f44064c..b23d7f4 100644
@@ -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;
 

@@ -1856,6 +1860,9 @@ static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 	BUG_ON(!service_tree);
 	BUG_ON(!service_tree->count);
 
+	if (!cfqd->cfq_slice_idle)
+		return false;
+
 	/* We never do for idle class queues. */
 	if (prio == IDLE_WORKLOAD)
 		return false;

@@ -1880,7 +1887,7 @@ 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

@@ -1896,8 +1903,13 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
 	/*
 	 * idle is disabled, either manually or by past process history
 	 */
-	if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq))
-		return;
+	if (!cfqd->cfq_slice_idle || !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

@@ -1924,13 +1936,21 @@ 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);
 }
 
 /*

@@ -1946,6 +1966,7 @@ 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)]++;

@@ -2215,7 +2236,7 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
 			cfqq = NULL;
 			goto keep_queue;
 		} else
-			goto expire;
+			goto check_group_idle;
 	}
 
 	/*

@@ -2249,6 +2270,17 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
 		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;
+	}
+
 expire:
 	cfq_slice_expired(cfqd, 0);
 new_queue:

@@ -3391,6 +3423,7 @@ 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));

@@ -3420,7 +3453,10 @@ 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");
 		}

@@ -3865,6 +3901,7 @@ 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;

@@ -3937,6 +3974,7 @@ 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);

@@ -3969,6 +4007,7 @@ 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,

@@ -3990,6 +4029,7 @@ 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

@@ -4043,6 +4083,12 @@ 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;
 

index b23d7f4..1f0d4ea 100644
@@ -148,6 +148,8 @@ struct cfq_queue {
 	struct cfq_queue *new_cfqq;
 	struct cfq_group *cfqg;
 	struct cfq_group *orig_cfqg;
+	/* Number of sectors dispatched from queue in single dispatch round */
+	unsigned long nr_sectors;
 };
 
 /*

@@ -926,8 +928,8 @@ static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)
 			slice_used = cfqq->allocated_slice;
 	}
 
-	cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u, sl_disp=%u", slice_used,
-			cfqq->slice_dispatch);
+	cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u, disp=%u sect=%u",
+			slice_used, cfqq->slice_dispatch, cfqq->nr_sectors);
 	return slice_used;
 }
 

@@ -1608,6 +1610,7 @@ static void __cfq_set_active_queue(struct cfq_data *cfqd,
 		cfqq->allocated_slice = 0;
 		cfqq->slice_end = 0;
 		cfqq->slice_dispatch = 0;
+		cfqq->nr_sectors = 0;
 
 		cfq_clear_cfqq_wait_request(cfqq);
 		cfq_clear_cfqq_must_dispatch(cfqq);

@@ -1970,6 +1973,7 @@ static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
 	elv_dispatch_sort(q, rq);
 
 	cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
+	cfqq->nr_sectors += blk_rq_sectors(rq);
 	cfq_blkiocg_update_dispatch_stats(&cfqq->cfqg->blkg, blk_rq_bytes(rq),
 					rq_data_dir(rq), rq_is_sync(rq));
 }