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| author | Paolo Valente <paolo.valente@linaro.org> | 2021-06-19 16:09:48 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2021-06-21 15:03:41 -0600 |
| commit | 9a2ac41b13c573703d6689f51f3e27dd658324be (patch) | |
| tree | 9b1815feafb49eb8c3e1404ae8bfc88b880208e3 /block/bfq-iosched.c | |
| parent | efc72524b3a9e4e7bc7c07f756528736409ec1b7 (diff) | |
| download | linux-9a2ac41b13c573703d6689f51f3e27dd658324be.tar.bz2 | |
block, bfq: reset waker pointer with shared queues
Commit 85686d0dc194 ("block, bfq: keep shared queues out of the waker
mechanism") leaves shared bfq_queues out of the waker-detection
mechanism. It attains this goal by not updating the pointer
last_completed_rq_bfqq, if the last request completed belongs to a
shared bfq_queue (so that the pointer will not point to the shared
bfq_queue).
Yet this has a side effect: the pointer last_completed_rq_bfqq keeps
pointing, deceptively, to a bfq_queue that actually is not the last
one to have had a request completed. As a consequence, such a
bfq_queue may deceptively be considered as a waker of some bfq_queue,
even of some shared bfq_queue.
To address this issue, reset last_completed_rq_bfqq if the last
request completed belongs to a shared queue.
Fixes: 85686d0dc194 ("block, bfq: keep shared queues out of the waker mechanism")
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Link: https://lore.kernel.org/r/20210619140948.98712-8-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/bfq-iosched.c')
| -rw-r--r-- | block/bfq-iosched.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index a273b2bcea2a..fedb0a8fd388 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -6165,11 +6165,13 @@ static void bfq_completed_request(struct bfq_queue *bfqq, struct bfq_data *bfqd) * of other queues. But a false waker will unjustly steal * bandwidth to its supposedly woken queue. So considering * also shared queues in the waking mechanism may cause more - * control troubles than throughput benefits. Then do not set - * last_completed_rq_bfqq to bfqq if bfqq is a shared queue. + * control troubles than throughput benefits. Then reset + * last_completed_rq_bfqq if bfqq is a shared queue. */ if (!bfq_bfqq_coop(bfqq)) bfqd->last_completed_rq_bfqq = bfqq; + else + bfqd->last_completed_rq_bfqq = NULL; /* * If we are waiting to discover whether the request pattern |