Re: [PATCH 2/2] block/mq-deadline: fallback to per-cpu insertion buckets under contention

Jens Axboe
2024-01-18T18:33:30Z

On 1/18/24 11:31 AM, Bart Van Assche wrote:
> On 1/18/24 10:04, Jens Axboe wrote:
>> If we attempt to insert a list of requests but someone else is already
>> running an insertion, then fallback to queueing it internally and let
>> the existing inserter finish the operation.
>
> Because this patch adds significant complexity: what are the use cases
> that benefit from this kind of optimization? Are these perhaps workloads
> on systems with many CPU cores and fast storage? If the storage is fast,
> why to use mq-deadline instead of "none" as I/O-scheduler?

You and others complain that mq-deadline is slow and doesn't scale,
these two patches help improve that situation. Not sure why this is even
a question?

--
Jens Axboe