lkml.org 
[lkml]   [2009]   [Nov]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 15/20] blkio: Take care of preemptions across groups
Date
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


\
 
 \ /
  Last update: 2009-11-04 00:47    [W:0.374 / U:0.324 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site