Messages in this thread | | | From | Chaitanya Kulkarni <> | Subject | Re: [PATCH v2] blk-ioprio: Introduce promote-to-rt policy | Date | Tue, 21 Feb 2023 18:04:03 +0000 |
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On 2/20/2023 5:54 AM, Hou Tao wrote: > From: Hou Tao <houtao1@huawei.com> > > 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 <houtao1@huawei.com>
Thanks for updating documentation and adding meaningful comment.
Looks good.
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
-ck
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