Commit c04645e5 authored Dec 03, 2009 by Vivek Goyal Committed by Jens Axboe Dec 03, 2009

blkio: Wait on sync-noidle queue even if rq_noidle = 1



o rq_noidle() is supposed to tell cfq that do not expect a request after this
  one, hence don't idle. But this does not seem to work very well. For example
  for direct random readers, rq_noidle = 1 but there is next request coming
  after this. Not idling, leads to a group not getting its share even if
  group_isolation=1.

o The right solution for this issue is to scan the higher layers and set
  right flag (WRITE_SYNC or WRITE_ODIRECT). For the time being, this single
  line fix helps. This should not have any significant impact when we are
  not using cgroups. I will later figure out IO paths in higher layer and
  fix it.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

parent ae30c286

block/cfq-iosched.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -3314,7 +3314,8 @@ static void cfq_completed_request(struct request_queue q, struct request rq)
		* only if we processed at least one !rq_noidle request
		*/
		if (cfqd->serving_type == SYNC_WORKLOAD
		\|\| cfqd->noidle_tree_requires_idle)
		\|\| cfqd->noidle_tree_requires_idle
		\|\| cfqq->cfqg->nr_cfqq == 1)
		cfq_arm_slice_timer(cfqd);
		}
		}

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