kernel/linux.git/block/bfq-iosched.h, branch v7.1

block, bfq: update outdated comment

2026-01-01T15:57:37+00:00

The function bfq_bfqq_may_idle() was renamed as bfq_better_to_idle() in commit 277a4a9b56cd ("block, bfq: give a better name to bfq_bfqq_may_idle"). Update the comment accordingly. Signed-off-by: Julia Lawall Signed-off-by: Jens Axboe

lib/sbitmap: convert shallow_depth from one word to the whole sbitmap

2025-08-07T12:30:17+00:00

Currently elevators will record internal 'async_depth' to throttle asynchronous requests, and they both calculate shallow_dpeth based on sb->shift, with the respect that sb->shift is the available tags in one word. However, sb->shift is not the availbale tags in the last word, see __map_depth: if (index == sb->map_nr - 1) return sb->depth - (index << sb->shift); For consequence, if the last word is used, more tags can be get than expected, for example, assume nr_requests=256 and there are four words, in the worst case if user set nr_requests=32, then the first word is the last word, and still use bits per word, which is 64, to calculate async_depth is wrong. One the ohter hand, due to cgroup qos, bfq can allow only one request to be allocated, and set shallow_dpeth=1 will still allow the number of words request to be allocated. Fix this problems by using shallow_depth to the whole sbitmap instead of per word, also change kyber, mq-deadline and bfq to follow this, a new helper __map_depth_with_shallow() is introduced to calculate available bits in each word. Signed-off-by: Yu Kuai Link: https://lore.kernel.org/r/20250807032413.1469456-2-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe

block, bfq: Reorder struct bfq_iocq_bfqq_data

2025-08-04T15:22:44+00:00

The size of struct bfq_iocq_bfqq_data can be reduced by moving a few fields around. On a x86_64, with allmodconfig, this shrinks the size from 144 to 128 bytes. The main benefit is to reduce the size of struct bfq_io_cq from 1360 to 1232. This structure is stored in a dedicated slab cache. So reducing its size improves cache usage. Signed-off-by: Christophe JAILLET Reviewed-by: Yu Kuai Link: https://lore.kernel.org/r/79394db1befaa658e8066b8e3348073ce27d9d26.1754119538.git.christophe.jaillet@wanadoo.fr Signed-off-by: Jens Axboe

block, bfq: remove bfq_log_bfqg()

2024-09-10T22:32:09+00:00

It's not used, hence can be removed. Signed-off-by: Yu Kuai Link: https://lore.kernel.org/r/20240909134154.954924-5-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe

block, bfq: use bfq_reassign_last_bfqq() in bfq_bfqq_move()

2024-09-03T15:51:54+00:00

Instead of open coding it, there are no functional changes. Signed-off-by: Yu Kuai Link: https://lore.kernel.org/r/20240902130329.3787024-5-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe

block, bfq: remove blkg_path()

2024-06-18T15:22:45+00:00

After commit 35fe6d763229 ("block: use standard blktrace API to output cgroup info for debug notes"), the field 'bfqg->blkg_path' is not used and hence can be removed, and therefor blkg_path() is not used anymore and can be removed. Signed-off-by: Yu Kuai Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/20240618032753.3502528-1-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe

block, bfq: remove BFQ_WEIGHT_LEGACY_DFL

2023-04-06T22:17:32+00:00

BFQ_WEIGHT_LEGACY_DFL is the same as CGROUP_WEIGHT_DFL, which means we don't need cpd_bind_fn() callback to update default weight when attached to a hierarchy. This patch remove BFQ_WEIGHT_LEGACY_DFL and cpd_bind_fn(). Signed-off-by: Chengming Zhou Acked-by: Tejun Heo Link: https://lore.kernel.org/r/20230406145050.49914-2-zhouchengming@bytedance.com Signed-off-by: Jens Axboe

block, bfq: cleanup 'bfqg->online'

2023-02-07T17:20:59+00:00

After commit dfd6200a0954 ("blk-cgroup: support to track if policy is online"), there is no need to do this again in bfq. However, 'pd->online' is not protected by 'bfqd->lock', in order to make sure bfq won't see that 'pd->online' is still set after bfq_pd_offline(), clear it before bfq_pd_offline() is called. This is fine because other polices doesn't use 'pd->online' and bfq_pd_offline() will move active bfqq to root cgroup anyway. Signed-off-by: Yu Kuai Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/20230202134913.2364549-1-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe

block, bfq: remove unused bfq_wr_max_time in struct bfq_data

2023-01-30T03:03:49+00:00

bfqd->bfq_wr_max_time is set to 0 in bfq_init_queue and is never changed. It is only used in bfq_wr_duration when bfq_wr_max_time > 0 which never meets, so bfqd->bfq_wr_max_time is not used actually. Just remove it. Signed-off-by: Kemeng Shi Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/20230116095153.3810101-9-shikemeng@huaweicloud.com Signed-off-by: Jens Axboe

block, bfq: inject I/O to underutilized actuators

2023-01-29T22:18:33+00:00

The main service scheme of BFQ for sync I/O is serving one sync bfq_queue at a time, for a while. In particular, BFQ enforces this scheme when it deems the latter necessary to boost throughput or to preserve service guarantees. Unfortunately, when BFQ enforces this policy, only one actuator at a time gets served for a while, because each bfq_queue contains I/O only for one actuator. The other actuators may remain underutilized. Actually, BFQ may serve (inject) extra I/O, taken from other bfq_queues, in parallel with that of the in-service queue. This injection mechanism may provide the ground for dealing also with the above actuator-underutilization problem. Yet BFQ does not take the actuator load into account when choosing which queue to pick extra I/O from. In addition, BFQ may happen to inject extra I/O only when the in-service queue is temporarily empty. In view of these facts, this commit extends the injection mechanism in such a way that the latter: (1) takes into account also the actuator load; (2) checks such a load on each dispatch, and injects I/O for an underutilized actuator, if there is one and there is I/O for it. To perform the check in (2), this commit introduces a load threshold, currently set to 4. A linear scan of each actuator is performed, until an actuator is found for which the following two conditions hold: the load of the actuator is below the threshold, and there is at least one non-in-service queue that contains I/O for that actuator. If such a pair (actuator, queue) is found, then the head request of that queue is returned for dispatch, instead of the head request of the in-service queue. We have set the threshold, empirically, to the minimum possible value for which an actuator is fully utilized, or close to be fully utilized. By doing so, injected I/O 'steals' as few drive-queue slots as possibile to the in-service queue. This reduces as much as possible the probability that the service of I/O from the in-service bfq_queue gets delayed because of slot exhaustion, i.e., because all the slots of the drive queue are filled with I/O injected from other queues (NCQ provides for 32 slots). This new mechanism also counters actuator underutilization in the case of asymmetric configurations of bfq_queues. Namely if there are few bfq_queues containing I/O for some actuators and many bfq_queues containing I/O for other actuators. Or if the bfq_queues containing I/O for some actuators have lower weights than the other bfq_queues. Reviewed-by: Damien Le Moal Signed-off-by: Paolo Valente Signed-off-by: Davide Zini Link: https://lore.kernel.org/r/20230103145503.71712-8-paolo.valente@linaro.org Signed-off-by: Jens Axboe