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SubjectRe: Do not overload dispatch queue (Was: Re: IO scheduler based IO controller V10)
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Wrong one.  Let's try the post java version instead.

8e29675: "implement slower async initiate and queue ramp up" introduced a
throughput regression for concurrent reader vs writer. Adjusting async delay
to use cfq_slice_async restored throughput.

Signed-off-by: Mike Galbraith <efault@gmx.de>

---
block/cfq-iosched.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
Index: linux-2.6/block/cfq-iosched.c
===================================================================
--- linux-2.6.orig/block/cfq-iosched.c
+++ linux-2.6/block/cfq-iosched.c
@@ -1343,17 +1343,18 @@ static int cfq_dispatch_requests(struct
*/
if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_desktop) {
unsigned long last_sync = jiffies - cfqd->last_end_sync_rq;
+ unsigned long slice = cfq_slice_async;
unsigned int depth;

/*
* must wait a bit longer
*/
- if (last_sync < cfq_slice_sync) {
- cfq_schedule_dispatch(cfqd, cfq_slice_sync - last_sync);
+ if (last_sync < slice) {
+ cfq_schedule_dispatch(cfqd, slice - last_sync);
return 0;
}

- depth = last_sync / cfq_slice_sync;
+ depth = last_sync / slice;
if (depth < max_dispatch)
max_dispatch = depth;
}



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