Please disregard the patch. I should send it to block mail list instead of bpf mail list. Sorry for the noise. On 2/23/2023 9:48 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. > > Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx> > Acked-by: Tejun Heo <tj@xxxxxxxxxx> > Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx> > Reviewed-by: Chaitanya Kulkarni <kch@xxxxxxxxxx> > --- > v3: > * 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