Messages in this thread Patch in this message | | | From | Corrado Zoccolo <> | Subject | [PATCH 2/4] cfq-iosched: fix no-idle preemption logic | Date | Tue, 24 Nov 2009 14:49:02 +0100 |
| |
An incoming no-idle queue should preempt the active no-idle queue only if the active queue is idling due to service tree empty. Previous code was buggy in two ways: * it relied on service_tree field to be set on the active queue, while it is not set when the code is idling for a new request * it didn't check for the service tree empty condition, so could lead to LIFO behaviour if multiple queues with depth > 1 were preempting each other on an non-NCQ device.
Reported-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com> --- block/cfq-iosched.c | 5 +++-- 1 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 6925ab9..2a304f4 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -2401,8 +2401,9 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, if (cfq_class_idle(cfqq)) return true; - if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD - && new_cfqq->service_tree == cfqq->service_tree) + if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD && + cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD && + new_cfqq->service_tree->count == 1) return true; /* -- 1.6.2.5
| |