diff options
Diffstat (limited to 'block/bfq-iosched.c')
| -rw-r--r-- | block/bfq-iosched.c | 38 |
1 files changed, 23 insertions, 15 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 95a19d1fbedf..83a2225e407b 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -2091,20 +2091,19 @@ static void bfq_update_io_intensity(struct bfq_queue *bfqq, u64 now_ns) * aspect, see the comments on the choice of the queue for injection * in bfq_select_queue(). * - * Turning back to the detection of a waker queue, a queue Q is deemed - * as a waker queue for bfqq if, for three consecutive times, bfqq - * happens to become non empty right after a request of Q has been - * completed. In this respect, even if bfqq is empty, we do not check - * for a waker if it still has some in-flight I/O. In fact, in this - * case bfqq is actually still being served by the drive, and may - * receive new I/O on the completion of some of the in-flight - * requests. In particular, on the first time, Q is tentatively set as - * a candidate waker queue, while on the third consecutive time that Q - * is detected, the field waker_bfqq is set to Q, to confirm that Q is - * a waker queue for bfqq. These detection steps are performed only if - * bfqq has a long think time, so as to make it more likely that - * bfqq's I/O is actually being blocked by a synchronization. This - * last filter, plus the above three-times requirement, make false + * Turning back to the detection of a waker queue, a queue Q is deemed as a + * waker queue for bfqq if, for three consecutive times, bfqq happens to become + * non empty right after a request of Q has been completed within given + * timeout. In this respect, even if bfqq is empty, we do not check for a waker + * if it still has some in-flight I/O. In fact, in this case bfqq is actually + * still being served by the drive, and may receive new I/O on the completion + * of some of the in-flight requests. In particular, on the first time, Q is + * tentatively set as a candidate waker queue, while on the third consecutive + * time that Q is detected, the field waker_bfqq is set to Q, to confirm that Q + * is a waker queue for bfqq. These detection steps are performed only if bfqq + * has a long think time, so as to make it more likely that bfqq's I/O is + * actually being blocked by a synchronization. This last filter, plus the + * above three-times requirement and time limit for detection, make false * positives less likely. * * NOTE @@ -2136,8 +2135,16 @@ static void bfq_check_waker(struct bfq_data *bfqd, struct bfq_queue *bfqq, bfqd->last_completed_rq_bfqq == bfqq->waker_bfqq) return; + /* + * We reset waker detection logic also if too much time has passed + * since the first detection. If wakeups are rare, pointless idling + * doesn't hurt throughput that much. The condition below makes sure + * we do not uselessly idle blocking waker in more than 1/64 cases. + */ if (bfqd->last_completed_rq_bfqq != - bfqq->tentative_waker_bfqq) { + bfqq->tentative_waker_bfqq || + now_ns > bfqq->waker_detection_started + + 128 * (u64)bfqd->bfq_slice_idle) { /* * First synchronization detected with a * candidate waker queue, or with a different @@ -2146,6 +2153,7 @@ static void bfq_check_waker(struct bfq_data *bfqd, struct bfq_queue *bfqq, bfqq->tentative_waker_bfqq = bfqd->last_completed_rq_bfqq; bfqq->num_waker_detections = 1; + bfqq->waker_detection_started = now_ns; } else /* Same tentative waker queue detected again */ bfqq->num_waker_detections++; |