cfq-iosched: fix the delay of cfq_group's vdisktime under iops mode (5be6b756) · Commits · 戴 / test

When adding a cfq_group into the cfq service tree, we use CFQ_IDLE_DELAY as the delay of cfq_group's vdisktime if there have been other cfq_groups already. When cfq is under iops mode, commit ("cfq-iosched: Convert from jiffies to nanoseconds") could result in a large iops delay and lead to an abnormal io schedule delay for the added cfq_group. To fix it, we just need to revert to the old CFQ_IDLE_DELAY value: HZ / 5 when iops mode is enabled. Despite having the same value, the delay of a cfq_queue in idle class and the delay of cfq_group are different things, so I define two new macros for the delay of a cfq_group under time-slice mode and iops mode. Fixes: ("cfq-iosched: Convert from jiffies to nanoseconds") Cc: <stable@vger.kernel.org> # 4.8+ Signed-off-by:

Hou Tao <houtao1@huawei.com> Acked-by:

Jan Kara <jack@suse.cz> Signed-off-by:

Jens Axboe <axboe@fb.com>

block/cfq-iosched.c

+15 −2

Original line number	Diff line number	Diff line
		@@ -38,9 +38,13 @@ static const u64 cfq_target_latency = (u64)NSEC_PER_SEC * 3/10; /* 300 ms */
		static const int cfq_hist_divisor = 4;

		/*
		* offset from end of service tree
		* offset from end of queue service tree for idle class
		*/
		#define CFQ_IDLE_DELAY (NSEC_PER_SEC / 5)
		/* offset from end of group service tree under time slice mode */
		#define CFQ_SLICE_MODE_GROUP_DELAY (NSEC_PER_SEC / 5)
		/* offset from end of group service under IOPS mode */
		#define CFQ_IOPS_MODE_GROUP_DELAY (HZ / 5)

		/*
		* below this threshold, we consider thinktime immediate
		@@ -1362,6 +1366,14 @@ cfq_group_service_tree_add(struct cfq_rb_root st, struct cfq_group cfqg)
		cfqg->vfraction = max_t(unsigned, vfr, 1);
		}

		static inline u64 cfq_get_cfqg_vdisktime_delay(struct cfq_data *cfqd)
		{
		if (!iops_mode(cfqd))
		return CFQ_SLICE_MODE_GROUP_DELAY;
		else
		return CFQ_IOPS_MODE_GROUP_DELAY;
		}

		static void
		cfq_group_notify_queue_add(struct cfq_data cfqd, struct cfq_group cfqg)
		{
		@@ -1381,7 +1393,8 @@ cfq_group_notify_queue_add(struct cfq_data cfqd, struct cfq_group cfqg)
		n = rb_last(&st->rb);
		if (n) {
		__cfqg = rb_entry_cfqg(n);
		cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
		cfqg->vdisktime = __cfqg->vdisktime +
		cfq_get_cfqg_vdisktime_delay(cfqd);
		} else
		cfqg->vdisktime = st->min_vdisktime;
		cfq_group_service_tree_add(st, cfqg);

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