ping ? On 5/8/2023 8:08 PM, Hou Tao wrote: > ping ? > > On 4/28/2023 3:44 PM, Hou Tao wrote: >> From: Hou Tao <houtao1@xxxxxxxxxx> >> >> Since commit a78418e6a04c ("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@xxxxxxxxxx> >> Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx> >> Reviewed-by: Chaitanya Kulkarni <kch@xxxxxxxxxx> >> Reviewed-by: Jan Kara <jack@xxxxxxx> >> Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx> >> --- >> v4: >> * rebased on 33afd4b76393 >> * Add Reviewed-by from Jan Kara >> >> v3: https://lore.kernel.org/linux-block/20230223135154.3749088-1-houtao@xxxxxxxxxxxxxxx >> * Use 'non-RT' instead of 'no-RT' in document (from Bagas) >> * Remove repeated sentence in commit message >> * Add Reviewed-by and Acked-by tags >> >> v2: https://lore.kernel.org/linux-block/20230220135428.2632906-1-houtao@xxxxxxxxxxxxxxx >> >> * Simplify the implementation of promote-to-rt (from Bart) >> * Make none-to-rt to work again by treating it as an alias of >> the promote-to-rt policy (from Bart & Jan) >> * fix the style of new content in cgroup-v2.rst (from Bagas) >> * set the default priority level to 4 instead of 0 for promote-to-rt >> >> v1: https://lore.kernel.org/linux-block/20230201045227.2203123-1-houtao@xxxxxxxxxxxxxxx >> >> Documentation/admin-guide/cgroup-v2.rst | 42 ++++++++++++++----------- >> block/blk-ioprio.c | 23 ++++++++++++-- >> 2 files changed, 44 insertions(+), 21 deletions(-) >> >> diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst >> index f67c0829350b..7544ce00e0cb 100644 >> --- a/Documentation/admin-guide/cgroup-v2.rst >> +++ b/Documentation/admin-guide/cgroup-v2.rst >> @@ -2024,31 +2024,33 @@ that attribute: >> no-change >> Do not modify the I/O priority class. >> >> - none-to-rt >> - For requests that do not have an I/O priority class (NONE), >> - change the I/O priority class into RT. Do not modify >> - the I/O priority class of other requests. >> + promote-to-rt >> + For requests that have a non-RT I/O priority class, change it into RT. >> + Also change the priority level of these requests to 4. Do not modify >> + the I/O priority of requests that have priority class RT. >> >> restrict-to-be >> For requests that do not have an I/O priority class or that have I/O >> - priority class RT, change it into BE. Do not modify the I/O priority >> - class of requests that have priority class IDLE. >> + priority class RT, change it into BE. Also change the priority level >> + of these requests to 0. Do not modify the I/O priority class of >> + requests that have priority class IDLE. >> >> idle >> Change the I/O priority class of all requests into IDLE, the lowest >> I/O priority class. >> >> + none-to-rt >> + Deprecated. Just an alias for promote-to-rt. >> + >> The following numerical values are associated with the I/O priority policies: >> >> -+-------------+---+ >> -| no-change | 0 | >> -+-------------+---+ >> -| none-to-rt | 1 | >> -+-------------+---+ >> -| rt-to-be | 2 | >> -+-------------+---+ >> -| all-to-idle | 3 | >> -+-------------+---+ >> ++----------------+---+ >> +| no-change | 0 | >> ++----------------+---+ >> +| rt-to-be | 2 | >> ++----------------+---+ >> +| all-to-idle | 3 | >> ++----------------+---+ >> >> The numerical value that corresponds to each I/O priority class is as follows: >> >> @@ -2064,9 +2066,13 @@ The numerical value that corresponds to each I/O priority class is as follows: >> >> The algorithm to set the I/O priority class for a request is as follows: >> >> -- Translate the I/O priority class policy into a number. >> -- Change the request I/O priority class into the maximum of the I/O priority >> - class policy number and the numerical I/O priority class. >> +- If I/O priority class policy is promote-to-rt, change the request I/O >> + priority class to IOPRIO_CLASS_RT and change the request I/O priority >> + level to 4. >> +- If I/O priorityt class is not promote-to-rt, translate the I/O priority >> + class policy into a number, then change the request I/O priority class >> + into the maximum of the I/O priority class policy number and the numerical >> + I/O priority class. >> >> PID >> --- >> diff --git a/block/blk-ioprio.c b/block/blk-ioprio.c >> index 055529b9b92b..4051fada01f1 100644 >> --- a/block/blk-ioprio.c >> +++ b/block/blk-ioprio.c >> @@ -23,25 +23,28 @@ >> /** >> * enum prio_policy - I/O priority class policy. >> * @POLICY_NO_CHANGE: (default) do not modify the I/O priority class. >> - * @POLICY_NONE_TO_RT: modify IOPRIO_CLASS_NONE into IOPRIO_CLASS_RT. >> + * @POLICY_PROMOTE_TO_RT: modify no-IOPRIO_CLASS_RT to IOPRIO_CLASS_RT. >> * @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_NONE_TO_RT: an alias for POLICY_PROMOTE_TO_RT. >> * >> * See also <linux/ioprio.h>. >> */ >> enum prio_policy { >> POLICY_NO_CHANGE = 0, >> - POLICY_NONE_TO_RT = 1, >> + POLICY_PROMOTE_TO_RT = 1, >> POLICY_RESTRICT_TO_BE = 2, >> POLICY_ALL_TO_IDLE = 3, >> + POLICY_NONE_TO_RT = 4, >> }; >> >> static const char *policy_name[] = { >> [POLICY_NO_CHANGE] = "no-change", >> - [POLICY_NONE_TO_RT] = "none-to-rt", >> + [POLICY_PROMOTE_TO_RT] = "promote-to-rt", >> [POLICY_RESTRICT_TO_BE] = "restrict-to-be", >> [POLICY_ALL_TO_IDLE] = "idle", >> + [POLICY_NONE_TO_RT] = "none-to-rt", >> }; >> >> static struct blkcg_policy ioprio_policy; >> @@ -189,6 +192,20 @@ void blkcg_set_ioprio(struct bio *bio) >> if (!blkcg || blkcg->prio_policy == POLICY_NO_CHANGE) >> return; >> >> + if (blkcg->prio_policy == POLICY_PROMOTE_TO_RT || >> + blkcg->prio_policy == POLICY_NONE_TO_RT) { >> + /* >> + * For RT threads, the default priority level is 4 because >> + * task_nice is 0. By promoting non-RT io-priority to RT-class >> + * and default level 4, those requests that are already >> + * RT-class but need a higher io-priority can use ioprio_set() >> + * to achieve this. >> + */ >> + if (IOPRIO_PRIO_CLASS(bio->bi_ioprio) != IOPRIO_CLASS_RT) >> + bio->bi_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_RT, 4); >> + return; >> + } >> + >> /* >> * Except for IOPRIO_CLASS_NONE, higher I/O priority numbers >> * correspond to a lower priority. Hence, the max_t() below selects > .