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| author | Shaohua Li <shaohua.li@intel.com> | 2009-12-03 12:58:05 +0100 |
|---|---|---|
| committer | Jens Axboe <jens.axboe@oracle.com> | 2009-12-03 12:58:05 +0100 |
| commit | 474b18ccc264c472abeec50f48469b6477202699 (patch) | |
| tree | 77c9f33d65b78266560b3aa0bea1c7d16fb45b2e /block/cfq-iosched.c | |
| parent | block: Allow devices to indicate whether discarded blocks are zeroed (diff) | |
| download | linux-474b18ccc264c472abeec50f48469b6477202699.tar.xz linux-474b18ccc264c472abeec50f48469b6477202699.zip | |
cfq-iosched: no dispatch limit for single queue
Since commit 2f5cb7381b737e24c8046fd4aeab571fb71315f5, each queue can send
up to 4 * 4 requests if only one queue exists. I wonder why we have such limit.
Device supports tag can send more requests. For example, AHCI can send 31
requests. Test (direct aio randread) shows the limits reduce about 4% disk
thoughput.
On the other hand, since we send one request one time, if other queue
pop when current is sending more than cfq_quantum requests, current queue will
stop send requests soon after one request, so sounds there is no big latency.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'block/cfq-iosched.c')
| -rw-r--r-- | block/cfq-iosched.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 71446497d7b6..f5b59e18ebd3 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -1618,9 +1618,9 @@ static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq) return false; /* - * Sole queue user, allow bigger slice + * Sole queue user, no limit */ - max_dispatch *= 4; + max_dispatch = -1; } /* |