diff options
Diffstat (limited to 'block/bfq-iosched.c')
| -rw-r--r-- | block/bfq-iosched.c | 18 |
1 files changed, 13 insertions, 5 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index d42a229b5a86..815b884d6c5a 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -4767,10 +4767,16 @@ bfq_find_active_bfqq_for_actuator(struct bfq_data *bfqd, int idx) /* * Perform a linear scan of each actuator, until an actuator is found - * for which the following two conditions hold: the load of the - * actuator is below the threshold (see comments on actuator_load_threshold - * for details), and there is a queue that contains I/O for that - * actuator. On success, return that queue. + * for which the following three conditions hold: the load of the + * actuator is below the threshold (see comments on + * actuator_load_threshold for details) and lower than that of the + * next actuator (comments on this extra condition below), and there + * is a queue that contains I/O for that actuator. On success, return + * that queue. + * + * Performing a plain linear scan entails a prioritization among + * actuators. The extra condition above breaks this prioritization and + * tends to distribute injection uniformly across actuators. */ static struct bfq_queue * bfq_find_bfqq_for_underused_actuator(struct bfq_data *bfqd) @@ -4778,7 +4784,9 @@ bfq_find_bfqq_for_underused_actuator(struct bfq_data *bfqd) int i; for (i = 0 ; i < bfqd->num_actuators; i++) { - if (bfqd->rq_in_driver[i] < bfqd->actuator_load_threshold) { + if (bfqd->rq_in_driver[i] < bfqd->actuator_load_threshold && + (i == bfqd->num_actuators - 1 || + bfqd->rq_in_driver[i] < bfqd->rq_in_driver[i+1])) { struct bfq_queue *bfqq = bfq_find_active_bfqq_for_actuator(bfqd, i); |