Re: [PATCH] blk-ioprio: Introduce promote-to-rt policy
From: Bart Van Assche <bvanassche@acm.org>
Date: 2023-02-01 17:34:27
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cgroups, linux-block, lkml
On 1/31/23 20:52, Hou Tao wrote:
quoted hunk ↗ jump to hunk
/** * enum prio_policy - I/O priority class policy. * @POLICY_NO_CHANGE: (default) do not modify the I/O priority class.@@ -27,21 +34,30 @@ * @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_PROMOTE_TO_RT: modify IOPRIO_CLASS_NONE and IOPRIO_CLASS_BE into + * IOPRIO_CLASS_RT. * See also <linux/ioprio.h>. */ enum prio_policy { - POLICY_NO_CHANGE = 0, - POLICY_NONE_TO_RT = 1, - POLICY_RESTRICT_TO_BE = 2, - POLICY_ALL_TO_IDLE = 3, + POLICY_NO_CHANGE = IOPRIO_CLASS_NONE, + POLICY_NONE_TO_RT = IOPRIO_CLASS_RT, + POLICY_RESTRICT_TO_BE = IOPRIO_CLASS_BE, + POLICY_ALL_TO_IDLE = IOPRIO_CLASS_IDLE, + POLICY_PROMOTE_TO_RT = IOPRIO_CLASS_RT | IOPRIO_POL_PROMOTION, +};
The above change complicates the ioprio code. Additionally, I'm concerned that it makes the ioprio code slower. Has it been considered to keep the numerical values for the existing policies, to assign the number 4 to POLICY_PROMOTE_TO_RT and to use a lookup-array in blkcg_set_ioprio() to convert the policy number into an IOPRIO_CLASS value? Thanks, Bart.