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authorAaron Carroll <aaronc@gelato.unsw.edu.au>2008-08-26 15:52:36 +0200
committerJens Axboe <jens.axboe@oracle.com>2008-10-09 08:56:09 +0200
commit45333d5a31296d0af886d94f1d08f128231cab8e (patch)
treeea5b1afb70fb17935128bac6df588e6b5ae764b4 /block/bsg.c
parent605401618ce4409045bc4db86e88d4b38f2ad585 (diff)
cfq-iosched: fix queue depth detection
CFQ's detection of queueing devices assumes a non-queuing device and detects if the queue depth reaches a certain threshold. Under some workloads (e.g. synchronous reads), CFQ effectively forces a unit queue depth, thus defeating the detection logic. This leads to poor performance on queuing hardware, since the idle window remains enabled. This patch inverts the sense of the logic: assume a queuing-capable device, and detect if the depth does not exceed the threshold. Signed-off-by: Aaron Carroll <aaronc@gelato.unsw.edu.au> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
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