[PATCH 2/2] io-controller: make rt preemption happen in the whole hierarchy

Gui Jianfeng
2009-06-26T08:14:23Z

let rt queue preempt non-rt queue if needed.
Make sure comparision happens at the same level.

Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
---
block/elevator-fq.c | 28 +++++++++++++++++++++++++++-
1 files changed, 27 insertions(+), 1 deletions(-)

diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index 1d4ec1f..21d38f5 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -3742,6 +3742,31 @@ int elv_iosched_expire_ioq(struct request_queue *q, int slice_expired,
return ret;
}

+static int check_rt_preemption(struct io_queue *ioq)
+{
+ struct hlist_node *node;
+ struct hlist_head *hhead = &ioq->efqd->rt_ioq_list;
+ struct io_queue *rt_ioq;
+ struct io_entity *entity = &ioq->entity;
+ struct io_entity *new_entity;
+
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(rt_ioq, node, hhead, rt_node) {
+ new_entity = &rt_ioq->entity;
+
+ bfq_find_matching_entity(&entity, &new_entity);
+
+ if (new_entity->ioprio_class == IOPRIO_CLASS_RT &&
+ entity->ioprio_class != IOPRIO_CLASS_RT) {
+ rcu_read_unlock();
+ return 1;
+ }
+ }
+ rcu_read_unlock();
+
+ return 0;
+}
+
/* Common layer function to select the next queue to dispatch from */
void *elv_fq_select_ioq(struct request_queue *q, int force)
{
@@ -3823,7 +3848,8 @@ void *elv_fq_select_ioq(struct request_queue *q, int force)
*/
iog = ioq_to_io_group(ioq);

- if (!elv_ioq_class_rt(ioq) && iog->busy_rt_queues) {
+ if (!elv_ioq_class_rt(ioq) &&
+ (iog->busy_rt_queues || check_rt_preemption(ioq))) {
/*
* We simulate this as cfqq timed out so that it gets to bank
* the remaining of its time slice.
--
1.5.4.rc3