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authorPaolo Valente <paolo.valente@linaro.org>2021-01-22 21:19:43 +0300
committerJens Axboe <axboe@kernel.dk>2021-01-25 04:18:24 +0300
commitb5f74ecacc3139ef873e69acc3aba28083ecc416 (patch)
tree8f370be89b909cd104670a7f19c8a805ee324ef3
parenta33df75c6328bf40078b35f2040d8e54d574c357 (diff)
downloadlinux-b5f74ecacc3139ef873e69acc3aba28083ecc416.tar.xz
block, bfq: use half slice_idle as a threshold to check short ttime
The value of the I/O plugging (idling) timeout is used also as the think-time threshold to decide whether a process has a short think time. In this respect, a good value of this timeout for rotational drives is un the order of several ms. Yet, this is often too long a time interval to be effective as a think-time threshold. This commit mitigates this problem (by a lot, according to tests), by halving the threshold. Tested-by: Jan Kara <jack@suse.cz> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--block/bfq-iosched.c7
1 files changed, 4 insertions, 3 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 9e4eb0fc1c16..eb2ca32d5b63 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -5238,12 +5238,13 @@ static void bfq_update_has_short_ttime(struct bfq_data *bfqd,
return;
/* Think time is infinite if no process is linked to
- * bfqq. Otherwise check average think time to
- * decide whether to mark as has_short_ttime
+ * bfqq. Otherwise check average think time to decide whether
+ * to mark as has_short_ttime. To this goal, compare average
+ * think time with half the I/O-plugging timeout.
*/
if (atomic_read(&bic->icq.ioc->active_ref) == 0 ||
(bfq_sample_valid(bfqq->ttime.ttime_samples) &&
- bfqq->ttime.ttime_mean > bfqd->bfq_slice_idle))
+ bfqq->ttime.ttime_mean > bfqd->bfq_slice_idle>>1))
has_short_ttime = false;
state_changed = has_short_ttime != bfq_bfqq_has_short_ttime(bfqq);