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Subject[PATCH] block: Improve think time sampling for CFQ
Date
Avoid taking a think time sample when the cfqq is not a sync queue or not
currently active or till its first request in the ongoing timeslice
completes.

Signed-off by: Divyesh Shah <dpshah@google.com>
---
This applies to Linus's kernel tree.
block/cfq-iosched.c | 15 +++++++++++----
1 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index fd7080e..1657d4f 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1904,10 +1904,17 @@ err:
}

static void
-cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
+cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
+ struct cfq_io_context *cic)
{
- unsigned long elapsed = jiffies - cic->last_end_request;
- unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
+ unsigned long elapsed, ttime;
+
+ if (!cfq_cfqq_sync(cfqq) || cfqq != cfqd->active_queue ||
+ cfq_cfqq_slice_new(cfqq))
+ return;
+
+ elapsed = jiffies - cic->last_end_request;
+ ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);

cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
@@ -2072,7 +2079,7 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
if (rq_is_meta(rq))
cfqq->meta_pending++;

- cfq_update_io_thinktime(cfqd, cic);
+ cfq_update_io_thinktime(cfqd, cfqq, cic);
cfq_update_io_seektime(cfqd, cic, rq);
cfq_update_idle_window(cfqd, cfqq, cic);



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