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block, bfq: use half slice_idle as a threshold to check short ttime

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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>
(cherry picked from commit b5f74ecacc3139ef873e69acc3aba28083ecc416)
(cherry picked from commit b1511c438e8a5668e6be04ad9107d6695332756c)
(cherry picked from commit 389992d9dc78340676248d0f01c7569b3db950ed)
(cherry picked from commit 49919eface6f4391cda0e77bcaad3e2786cbbab3)
(cherry picked from commit 87b015de51122ea9b5d9e56b846ae945db8444f0)
(cherry picked from commit 6ada34cdc94c89e97926a2d001412ecc027e1392)
(cherry picked from commit 2782bcc2919dd2a0a1d461d36c22338e67bc6327)
This commit is contained in:
Paolo Valente 2021-01-22 19:19:43 +01:00 committed by Ksawlii
parent fe945719eb
commit fbbabdb3bc
1 changed files with 4 additions and 3 deletions
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7
block/bfq-iosched.c
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@ -5349,12 +5349,13 @@ 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);