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Message-ID: <aedc240d-7c9e-248a-52d2-c9775f3e8ca1@acm.org>
Date: Fri, 3 Feb 2023 11:45:32 -0800
From: Bart Van Assche <bvanassche@....org>
To: Hou Tao <houtao@...weicloud.com>, linux-block@...r.kernel.org
Cc: Jan Kara <jack@...e.cz>, Jens Axboe <axboe@...nel.dk>,
cgroups@...r.kernel.org, Tejun Heo <tj@...nel.org>,
Zefan Li <lizefan.x@...edance.com>,
Johannes Weiner <hannes@...xchg.org>,
Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org, houtao1@...wei.com
Subject: Re: [PATCH] blk-ioprio: Introduce promote-to-rt policy
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)
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