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Subject[PATCH] io-controller: Preempt a non-rt queue if a rt ioq is present in ancestor or sibling groups
Preempt the ongoing non-rt ioq if there are rt ioqs waiting for dispatching
in ancestor or sibling groups. It will give other group's rt ioq an chance
to dispatch ASAP.

Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
---
block/elevator-fq.c | 44 +++++++++++++++++++++++++++++++++++++++-----
block/elevator-fq.h | 1 +
2 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index 2ad40eb..80526fd 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -3245,8 +3245,16 @@ void elv_add_ioq_busy(struct elv_fq_data *efqd, struct io_queue *ioq)
elv_mark_ioq_busy(ioq);
efqd->busy_queues++;
if (elv_ioq_class_rt(ioq)) {
+ struct io_entity *entity;
struct io_group *iog = ioq_to_io_group(ioq);
+
iog->busy_rt_queues++;
+ entity = iog->entity.parent;
+
+ for_each_entity(entity) {
+ iog = io_entity_to_iog(entity);
+ iog->sub_busy_rt_queues++;
+ }
}

#ifdef CONFIG_DEBUG_GROUP_IOSCHED
@@ -3290,9 +3298,18 @@ void elv_del_ioq_busy(struct elevator_queue *e, struct io_queue *ioq,
elv_clear_ioq_busy(ioq);
BUG_ON(efqd->busy_queues == 0);
efqd->busy_queues--;
+
if (elv_ioq_class_rt(ioq)) {
+ struct io_entity *entity;
struct io_group *iog = ioq_to_io_group(ioq);
+
iog->busy_rt_queues--;
+ entity = iog->entity.parent;
+
+ for_each_entity(entity) {
+ iog = io_entity_to_iog(entity);
+ iog->sub_busy_rt_queues--;
+ }
}

elv_deactivate_ioq(efqd, ioq, requeue);
@@ -3735,12 +3752,32 @@ int elv_iosched_expire_ioq(struct request_queue *q, int slice_expired,
return ret;
}

+static int check_rt_queue(struct io_queue *ioq)
+{
+ struct io_group *iog;
+ struct io_entity *entity;
+
+ iog = ioq_to_io_group(ioq);
+
+ if (iog->busy_rt_queues)
+ return 1;
+
+ entity = iog->entity.parent;
+
+ for_each_entity(entity) {
+ iog = io_entity_to_iog(entity);
+ if (iog->sub_busy_rt_queues)
+ return 1;
+ }
+
+ return 0;
+}
+
/* Common layer function to select the next queue to dispatch from */
void *elv_fq_select_ioq(struct request_queue *q, int force)
{
struct elv_fq_data *efqd = &q->elevator->efqd;
struct io_queue *new_ioq = NULL, *ioq = elv_active_ioq(q->elevator);
- struct io_group *iog;
int slice_expired = 1;

if (!elv_nr_busy_ioq(q->elevator))
@@ -3811,12 +3848,9 @@ void *elv_fq_select_ioq(struct request_queue *q, int force)
/*
* If we have a RT cfqq waiting, then we pre-empt the current non-rt
* cfqq.
- *
- * TODO: This does not seem right across the io groups. Fix it.
*/
- iog = ioq_to_io_group(ioq);

- if (!elv_ioq_class_rt(ioq) && iog->busy_rt_queues) {
+ if (!elv_ioq_class_rt(ioq) && check_rt_queue(ioq)) {
/*
* We simulate this as cfqq timed out so that it gets to bank
* the remaining of its time slice.
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index b3193f8..be6c1af 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -248,6 +248,7 @@ struct io_group {
* non-RT cfqq in service when this value is non-zero.
*/
unsigned int busy_rt_queues;
+ unsigned int sub_busy_rt_queues;

int deleting;
unsigned short iocg_id;
--
1.5.4.rc3



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