Messages in this thread Patch in this message | | | From | Vivek Goyal <> | Subject | [PATCH 15/20] blkio: Take care of preemptions across groups | Date | Tue, 3 Nov 2009 18:43:52 -0500 |
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o Additional preemption checks for groups where we travel up the hierarchy and see if one queue should preempt other or not.
o Also prevents preemption across groups in some cases to provide isolation between groups.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com> --- block/cfq-iosched.c | 33 +++++++++++++++++++++++++++++++++ 1 files changed, 33 insertions(+), 0 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 87b1799..98dbead 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -2636,6 +2636,36 @@ cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq, } } +static bool cfq_should_preempt_group(struct cfq_data *cfqd, + struct cfq_queue *cfqq, struct cfq_queue *new_cfqq) +{ + struct cfq_entity *cfqe = &cfqq->entity; + struct cfq_entity *new_cfqe = &new_cfqq->entity; + + if (cfqq_to_cfqg(cfqq) != &cfqd->root_group) + cfqe = parent_entity(&cfqq->entity); + + if (cfqq_to_cfqg(new_cfqq) != &cfqd->root_group) + new_cfqe = parent_entity(&new_cfqq->entity); + + /* + * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice. + */ + + if (new_cfqe->ioprio_class == IOPRIO_CLASS_RT + && cfqe->ioprio_class != IOPRIO_CLASS_RT) + return true; + /* + * Allow an BE request to pre-empt an ongoing IDLE clas timeslice. + */ + + if (new_cfqe->ioprio_class == IOPRIO_CLASS_BE + && cfqe->ioprio_class == IOPRIO_CLASS_IDLE) + return true; + + return false; +} + /* * Check if new_cfqq should preempt the currently active queue. Return 0 for * no or if we aren't sure, a 1 will cause a preempt. @@ -2666,6 +2696,9 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq)) return true; + if (cfqq_to_cfqg(new_cfqq) != cfqq_to_cfqg(cfqq)) + return cfq_should_preempt_group(cfqd, cfqq, new_cfqq); + /* * So both queues are sync. Let the new request get disk time if * it's a metadata request and the current queue is doing regular IO. -- 1.6.2.5
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