Re: [PATCH v2 1/5] blk-mq-sched: introduce high level elevator lock

[Hannes Reinecke]

On 7/30/25 10:22, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@xxxxxxxxxx>
>
> Currently, both mq-deadline and bfq have global spin lock that will be
> grabbed inside elevator methods like dispatch_request, insert_requests,
> and bio_merge. And the global lock is the main reason mq-deadline and
> bfq can't scale very well.
>
> While dispatching request, blk_mq_get_disatpch_budget() and
> blk_mq_get_driver_tag() must be called, and they are not ready to be called
> inside elevator methods, hence introduce a new method like
> dispatch_requests is not possible.
>
> Hence introduce a new high level elevator lock, currently it is protecting
> dispatch_request only. Following patches will convert mq-deadline and bfq
> to use this lock and finally support request batch dispatching by calling
> the method multiple time while holding the lock.
>
> Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> ---
>   block/blk-mq-sched.c | 6 ++++++
>   block/elevator.c     | 1 +
>   block/elevator.h     | 4 ++--
>   3 files changed, 9 insertions(+), 2 deletions(-)
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>

Cheers,

Hannes
--
Dr. Hannes Reinecke                  Kernel Storage Architect
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