blk-ioprio: Introduce promote-to-rt policy
Since commit a78418e6a0
("block: Always initialize bio IO priority on
submit"), bio->bi_ioprio will never be IOPRIO_CLASS_NONE when calling
blkcg_set_ioprio(), so there will be no way to promote the io-priority
of one cgroup to IOPRIO_CLASS_RT, because bi_ioprio will always be
greater than or equals to IOPRIO_CLASS_RT.
It seems possible to call blkcg_set_ioprio() first then try to
initialize bi_ioprio later in bio_set_ioprio(), but this doesn't work
for bio in which bi_ioprio is already initialized (e.g., direct-io), so
introduce a new promote-to-rt policy to promote the iopriority of bio to
IOPRIO_CLASS_RT if the ioprio is not already RT.
For none-to-rt policy, although it doesn't work now, but considering
that its purpose was also to override the io-priority to RT and allowing
for a smoother transition, just keep it and treat it as an alias of
the promote-to-rt policy.
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Hou Tao <houtao1@huawei.com>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Link: https://lore.kernel.org/r/20230428074404.280532-1-houtao@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
parent
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@ -2024,31 +2024,33 @@ that attribute:
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no-change
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no-change
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Do not modify the I/O priority class.
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Do not modify the I/O priority class.
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none-to-rt
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promote-to-rt
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For requests that do not have an I/O priority class (NONE),
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For requests that have a non-RT I/O priority class, change it into RT.
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change the I/O priority class into RT. Do not modify
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Also change the priority level of these requests to 4. Do not modify
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the I/O priority class of other requests.
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the I/O priority of requests that have priority class RT.
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restrict-to-be
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restrict-to-be
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For requests that do not have an I/O priority class or that have I/O
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For requests that do not have an I/O priority class or that have I/O
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priority class RT, change it into BE. Do not modify the I/O priority
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priority class RT, change it into BE. Also change the priority level
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class of requests that have priority class IDLE.
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of these requests to 0. Do not modify the I/O priority class of
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requests that have priority class IDLE.
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idle
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idle
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Change the I/O priority class of all requests into IDLE, the lowest
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Change the I/O priority class of all requests into IDLE, the lowest
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I/O priority class.
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I/O priority class.
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none-to-rt
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Deprecated. Just an alias for promote-to-rt.
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The following numerical values are associated with the I/O priority policies:
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The following numerical values are associated with the I/O priority policies:
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+-------------+---+
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+----------------+---+
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| no-change | 0 |
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| no-change | 0 |
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+-------------+---+
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+----------------+---+
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| none-to-rt | 1 |
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| rt-to-be | 2 |
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+-------------+---+
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+----------------+---+
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| rt-to-be | 2 |
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| all-to-idle | 3 |
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+-------------+---+
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+----------------+---+
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| all-to-idle | 3 |
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+-------------+---+
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The numerical value that corresponds to each I/O priority class is as follows:
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The numerical value that corresponds to each I/O priority class is as follows:
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@ -2064,9 +2066,13 @@ The numerical value that corresponds to each I/O priority class is as follows:
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The algorithm to set the I/O priority class for a request is as follows:
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The algorithm to set the I/O priority class for a request is as follows:
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- Translate the I/O priority class policy into a number.
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- If I/O priority class policy is promote-to-rt, change the request I/O
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- Change the request I/O priority class into the maximum of the I/O priority
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priority class to IOPRIO_CLASS_RT and change the request I/O priority
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class policy number and the numerical I/O priority class.
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level to 4.
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- If I/O priorityt class is not promote-to-rt, translate the I/O priority
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class policy into a number, then change the request I/O priority class
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into the maximum of the I/O priority class policy number and the numerical
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I/O priority class.
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PID
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PID
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---
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---
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@ -23,25 +23,28 @@
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/**
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/**
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* enum prio_policy - I/O priority class policy.
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* enum prio_policy - I/O priority class policy.
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* @POLICY_NO_CHANGE: (default) do not modify the I/O priority class.
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* @POLICY_NO_CHANGE: (default) do not modify the I/O priority class.
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* @POLICY_NONE_TO_RT: modify IOPRIO_CLASS_NONE into IOPRIO_CLASS_RT.
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* @POLICY_PROMOTE_TO_RT: modify no-IOPRIO_CLASS_RT to IOPRIO_CLASS_RT.
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* @POLICY_RESTRICT_TO_BE: modify IOPRIO_CLASS_NONE and IOPRIO_CLASS_RT into
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* @POLICY_RESTRICT_TO_BE: modify IOPRIO_CLASS_NONE and IOPRIO_CLASS_RT into
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* IOPRIO_CLASS_BE.
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* IOPRIO_CLASS_BE.
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* @POLICY_ALL_TO_IDLE: change the I/O priority class into IOPRIO_CLASS_IDLE.
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* @POLICY_ALL_TO_IDLE: change the I/O priority class into IOPRIO_CLASS_IDLE.
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* @POLICY_NONE_TO_RT: an alias for POLICY_PROMOTE_TO_RT.
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*
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*
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* See also <linux/ioprio.h>.
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* See also <linux/ioprio.h>.
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*/
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*/
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enum prio_policy {
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enum prio_policy {
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POLICY_NO_CHANGE = 0,
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POLICY_NO_CHANGE = 0,
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POLICY_NONE_TO_RT = 1,
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POLICY_PROMOTE_TO_RT = 1,
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POLICY_RESTRICT_TO_BE = 2,
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POLICY_RESTRICT_TO_BE = 2,
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POLICY_ALL_TO_IDLE = 3,
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POLICY_ALL_TO_IDLE = 3,
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POLICY_NONE_TO_RT = 4,
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};
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};
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static const char *policy_name[] = {
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static const char *policy_name[] = {
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[POLICY_NO_CHANGE] = "no-change",
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[POLICY_NO_CHANGE] = "no-change",
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[POLICY_NONE_TO_RT] = "none-to-rt",
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[POLICY_PROMOTE_TO_RT] = "promote-to-rt",
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[POLICY_RESTRICT_TO_BE] = "restrict-to-be",
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[POLICY_RESTRICT_TO_BE] = "restrict-to-be",
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[POLICY_ALL_TO_IDLE] = "idle",
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[POLICY_ALL_TO_IDLE] = "idle",
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[POLICY_NONE_TO_RT] = "none-to-rt",
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};
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};
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static struct blkcg_policy ioprio_policy;
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static struct blkcg_policy ioprio_policy;
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@ -189,6 +192,20 @@ void blkcg_set_ioprio(struct bio *bio)
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if (!blkcg || blkcg->prio_policy == POLICY_NO_CHANGE)
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if (!blkcg || blkcg->prio_policy == POLICY_NO_CHANGE)
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return;
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return;
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if (blkcg->prio_policy == POLICY_PROMOTE_TO_RT ||
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blkcg->prio_policy == POLICY_NONE_TO_RT) {
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/*
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* For RT threads, the default priority level is 4 because
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* task_nice is 0. By promoting non-RT io-priority to RT-class
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* and default level 4, those requests that are already
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* RT-class but need a higher io-priority can use ioprio_set()
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* to achieve this.
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*/
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if (IOPRIO_PRIO_CLASS(bio->bi_ioprio) != IOPRIO_CLASS_RT)
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bio->bi_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_RT, 4);
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return;
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}
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/*
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/*
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* Except for IOPRIO_CLASS_NONE, higher I/O priority numbers
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* Except for IOPRIO_CLASS_NONE, higher I/O priority numbers
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* correspond to a lower priority. Hence, the max_t() below selects
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* correspond to a lower priority. Hence, the max_t() below selects
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