From: Hou Tao <[email protected]>
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 ioprio policy to promote the iopriority of bio to
IOPRIO_CLASS_RT if the ioprio is not already RT.
So introduce a new promote-to-rt policy to achieve this. 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 allow for a smoother
transition, just keep it and treat it as an alias of the promote-to-rt
policy.
Signed-off-by: Hou Tao <[email protected]>
---
v2:
* 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/[email protected]
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 74cec76be9f2..ccfb9fdfbc16 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -2021,31 +2021,33 @@ 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 no-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:
@@ -2061,9 +2063,13 @@ 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 8bb6b8eba4ce..4eba569d4823 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
--
2.29.2
On Mon, Feb 20, 2023 at 09:54:28PM +0800, Hou Tao wrote:
> From: Hou Tao <[email protected]>
>
> 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 ioprio policy to promote the iopriority of bio to
> IOPRIO_CLASS_RT if the ioprio is not already RT.
>
> So introduce a new promote-to-rt policy to achieve this. 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 allow for a smoother
> transition, just keep it and treat it as an alias of the promote-to-rt
> policy.
>
> Signed-off-by: Hou Tao <[email protected]>
Acked-by: Tejun Heo <[email protected]>
Thanks.
--
tejun
On 2/20/23 05:54, Hou Tao wrote:
> From: Hou Tao <[email protected]>
Reviewed-by: Bart Van Assche <[email protected]>
On 2/20/2023 5:54 AM, Hou Tao wrote:
> From: Hou Tao <[email protected]>
>
> 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 ioprio policy to promote the iopriority of bio to
> IOPRIO_CLASS_RT if the ioprio is not already RT.
>
> So introduce a new promote-to-rt policy to achieve this. 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 allow for a smoother
> transition, just keep it and treat it as an alias of the promote-to-rt
> policy.
>
> Signed-off-by: Hou Tao <[email protected]>
Thanks for updating documentation and adding meaningful comment.
Looks good.
Reviewed-by: Chaitanya Kulkarni <[email protected]>
-ck
On 2/20/23 20:54, Hou Tao wrote:
> diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
> index 74cec76be9f2..ccfb9fdfbc16 100644
> --- a/Documentation/admin-guide/cgroup-v2.rst
> +++ b/Documentation/admin-guide/cgroup-v2.rst
> @@ -2021,31 +2021,33 @@ 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 no-RT I/O priority class, change it into RT.
"non-RT" maybe? Or the original wording is better?
> + 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:
>
> @@ -2061,9 +2063,13 @@ 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
> ---
The rest is LGTM.
--
An old man doll... just what I always wanted! - Clara
Hi,
On 2/22/2023 3:38 PM, Bagas Sanjaya wrote:
> On 2/20/23 20:54, Hou Tao wrote:
>> diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
>> index 74cec76be9f2..ccfb9fdfbc16 100644
>> --- a/Documentation/admin-guide/cgroup-v2.rst
>> +++ b/Documentation/admin-guide/cgroup-v2.rst
>> @@ -2021,31 +2021,33 @@ 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 no-RT I/O priority class, change it into RT.
> "non-RT" maybe? Or the original wording is better?
Because promote-to-rt doesn't work like none-to-rt, so using the original word
is incorrect. Will fix it to non-RT in v3.
>> + 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:
>>
>> @@ -2061,9 +2063,13 @@ 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
>> ---
> The rest is LGTM.
Thanks for you review.
>
On Mon 20-02-23 21:54:28, Hou Tao wrote:
> From: Hou Tao <[email protected]>
>
> 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 ioprio policy to promote the iopriority of bio to
> IOPRIO_CLASS_RT if the ioprio is not already RT.
>
> So introduce a new promote-to-rt policy to achieve this. 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 allow for a smoother
> transition, just keep it and treat it as an alias of the promote-to-rt
> policy.
>
> Signed-off-by: Hou Tao <[email protected]>
Looks good to me. Feel free to add:
Reviewed-by: Jan Kara <[email protected]>
Just one question regarding doc below:
> ++----------------+---+
> +| no-change | 0 |
> ++----------------+---+
> +| rt-to-be | 2 |
> ++----------------+---+
> +| all-to-idle | 3 |
> ++----------------+---+
Shouldn't there be preempt-to-rt somewhere in this table as well? Or why
this this in the doc at all? I'd consider the numbers to be kernel internal
thing?
Honza
--
Jan Kara <[email protected]>
SUSE Labs, CR
Hi
On 2/27/2023 9:03 PM, Jan Kara wrote:
> On Mon 20-02-23 21:54:28, Hou Tao wrote:
>> From: Hou Tao <[email protected]>
>>
>> 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 ioprio policy to promote the iopriority of bio to
>> IOPRIO_CLASS_RT if the ioprio is not already RT.
>>
>> So introduce a new promote-to-rt policy to achieve this. 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 allow for a smoother
>> transition, just keep it and treat it as an alias of the promote-to-rt
>> policy.
>>
>> Signed-off-by: Hou Tao <[email protected]>
> Looks good to me. Feel free to add:
>
> Reviewed-by: Jan Kara <[email protected]>
Thanks for the review.
>
> Just one question regarding doc below:
>
>> ++----------------+---+
>> +| no-change | 0 |
>> ++----------------+---+
>> +| rt-to-be | 2 |
>> ++----------------+---+
>> +| all-to-idle | 3 |
>> ++----------------+---+
> Shouldn't there be preempt-to-rt somewhere in this table as well? Or why
> this this in the doc at all? I'd consider the numbers to be kernel internal
> thing?
These numbers are used in the algorithm paragraph below to explain how the final
ioprio is calculated. For prompt-to-rt policy, the algorithm is different and
the number is unnecessary.
> Honza
On Mon 27-02-23 21:56:25, Hou Tao wrote:
> Hi
>
> On 2/27/2023 9:03 PM, Jan Kara wrote:
> > On Mon 20-02-23 21:54:28, Hou Tao wrote:
> >> From: Hou Tao <[email protected]>
> >>
> >> 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 ioprio policy to promote the iopriority of bio to
> >> IOPRIO_CLASS_RT if the ioprio is not already RT.
> >>
> >> So introduce a new promote-to-rt policy to achieve this. 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 allow for a smoother
> >> transition, just keep it and treat it as an alias of the promote-to-rt
> >> policy.
> >>
> >> Signed-off-by: Hou Tao <[email protected]>
> > Looks good to me. Feel free to add:
> >
> > Reviewed-by: Jan Kara <[email protected]>
> Thanks for the review.
> >
> > Just one question regarding doc below:
> >
> >> ++----------------+---+
> >> +| no-change | 0 |
> >> ++----------------+---+
> >> +| rt-to-be | 2 |
> >> ++----------------+---+
> >> +| all-to-idle | 3 |
> >> ++----------------+---+
> > Shouldn't there be preempt-to-rt somewhere in this table as well? Or why
> > this this in the doc at all? I'd consider the numbers to be kernel internal
> > thing?
> These numbers are used in the algorithm paragraph below to explain how the final
> ioprio is calculated. For prompt-to-rt policy, the algorithm is different and
> the number is unnecessary.
I see, thanks for explanation.
Honza
--
Jan Kara <[email protected]>
SUSE Labs, CR