Re: [PATCH] blk-ioprio: Introduce promote-to-rt policy
From: Bart Van Assche <bvanassche@acm.org>
Date: 2023-02-03 19:45:40
Also in:
cgroups, linux-block, lkml
Subsystem:
block layer, the rest · Maintainers:
Jens Axboe, Linus Torvalds
On 2/2/23 17:48, Hou Tao wrote:
I don't get it on how to remove IOPRIO_POL_PROMOTION when calculating the final ioprio for bio. IOPRIO_POL_PROMOTION is not used for IOPRIO_CLASS values but used to determinate on how to calculate the final ioprio for bio: choosing the maximum or minimum between blkcg ioprio and original bio bi_ioprio.
Do the block layer code changes shown below implement the functionality that you need? Thanks, Bart.
diff --git a/block/blk-ioprio.c b/block/blk-ioprio.c
index 8bb6b8eba4ce..4a56da95168e 100644
--- a/block/blk-ioprio.c
+++ b/block/blk-ioprio.c@@ -27,6 +27,8 @@ * @POLICY_RESTRICT_TO_BE: modify IOPRIO_CLASS_NONE and IOPRIO_CLASS_RT into * IOPRIO_CLASS_BE. * @POLICY_ALL_TO_IDLE: change the I/O priority class into IOPRIO_CLASS_IDLE. + * @POLICY_PROMOTE_TO_RT: modify IOPRIO_CLASS_NONE and IOPRIO_CLASS_BE into + * IOPRIO_CLASS_RT. * * See also <linux/ioprio.h>. */
@@ -35,6 +37,7 @@ enum prio_policy { POLICY_NONE_TO_RT = 1, POLICY_RESTRICT_TO_BE = 2, POLICY_ALL_TO_IDLE = 3, + POLICY_PROMOTE_TO_RT, }; static const char *policy_name[] = {
@@ -42,6 +45,7 @@ static const char *policy_name[] = { [POLICY_NONE_TO_RT] = "none-to-rt", [POLICY_RESTRICT_TO_BE] = "restrict-to-be", [POLICY_ALL_TO_IDLE] = "idle", + [POLICY_PROMOTE_TO_RT] = "promote-to-rt", }; static struct blkcg_policy ioprio_policy;
@@ -189,17 +193,23 @@ void blkcg_set_ioprio(struct bio *bio) if (!blkcg || blkcg->prio_policy == POLICY_NO_CHANGE) return; - /* - * Except for IOPRIO_CLASS_NONE, higher I/O priority numbers - * correspond to a lower priority. Hence, the max_t() below selects - * the lower priority of bi_ioprio and the cgroup I/O priority class. - * If the bio I/O priority equals IOPRIO_CLASS_NONE, the cgroup I/O - * priority is assigned to the bio. - */ - prio = max_t(u16, bio->bi_ioprio, - IOPRIO_PRIO_VALUE(blkcg->prio_policy, 0)); - if (prio > bio->bi_ioprio) - bio->bi_ioprio = prio; + if (blkcg->prio_policy == PROMOTE_TO_RT) { + if (IOPRIO_PRIO_CLASS(bio->bi_ioprio) != IOPRIO_CLASS_RT) + bio->bi_ioprio = IOPRIO_CLASS_RT; + } else { + /* + * Except for IOPRIO_CLASS_NONE, higher I/O priority numbers + * correspond to a lower priority. Hence, the max_t() below + * selects the lower priority of bi_ioprio and the cgroup I/O + * priority class. If the bio I/O priority equals + * IOPRIO_CLASS_NONE, the cgroup I/O priority is assigned to the + * bio. + */ + prio = max_t(u16, bio->bi_ioprio, + IOPRIO_PRIO_VALUE(blkcg->prio_policy, 0)); + if (prio > bio->bi_ioprio) + bio->bi_ioprio = prio; + } } void blk_ioprio_exit(struct gendisk *disk)