Re: [PATCH] blk-ioprio: Introduce promote-to-rt policy

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 1/31/23 20:52, Hou Tao wrote:
diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index c8ae7c897f14..e0b9f73ef62a 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -2038,17 +2038,27 @@ that attribute:
  	Change the I/O priority class of all requests into IDLE, the lowest
  	I/O priority class.
+ promote-to-rt
+	For requests that have I/O priority class BE or that have I/O priority
+        class IDLE, change it into RT. Do not modify the I/O priority class
+        of requests that have priority class RT.

Please document whether or not this policy modifies the I/O priority
(IOPRIO_PRIO_DATA()). Do you agree that the I/O priority should be preserved
when promoting from BE to RT and that only the I/O priority class should be
modified for such promotions?

  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 |
-+-------------+---+
+
++---------------+---------+-----+
+| policy        | inst    | num |
++---------------+---------+-----+
+| no-change     | demote  | 0   |
++---------------+---------+-----+
+| none-to-rt    | demote  | 1   |
++---------------+---------+-----+
+| rt-to-be      | demote  | 2   |
++---------------+---------+-----+
+| idle          | demote  | 3   |
++---------------+---------+-----+
+| promote-to-rt | promote | 1   |
++---------------+---------+-----+

I prefer that this table is not modified. The numerical values associated with
policies only matters for none-to-rt, rt-to-be and all-to-idle but not for
promote-to-rt. So I don't think that it is necessary to mention a numerical
value for the promote-to-rt policy. Additionally, "none-to-rt" is not a policy
that demotes the I/O priority but a policy that may promote the I/O priority.

+-- If the instruction is promotion, change the request I/O priority class
+-  into the minimum of the I/O priority class policy number and the numerical
+-  I/O priority class.

Using the minimum value seems wrong to me because that will change
IOPRIO_VALUE(IOPRIO_CLASS_RT, 1) into IOPRIO_VALUE(IOPRIO_CLASS_RT, 0).

Thanks,

Bart.



[Index of Archives]     [Kernel Newbies]     [Security]     [Netfilter]     [Bugtraq]     [Linux FS]     [Yosemite Forum]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Samba]     [Video 4 Linux]     [Device Mapper]     [Linux Resources]

  Powered by Linux