Re: [PATCH 1/4] bio: add allocation cache abstraction

[Ming Lei <ming.lei@redhat.com>]

Hi Jens,

On Mon, Aug 09, 2021 at 03:23:58PM -0600, Jens Axboe wrote:
> Add a set of helpers that can encapsulate bio allocations, reusing them
> as needed. Caller must provide the necessary locking, if any is needed.
> The primary intended use case is polled IO from io_uring, which will not
> need any external locking.
> 
> Very simple - keeps a count of bio's in the cache, and maintains a max
> of 512 with a slack of 64. If we get above max + slack, we drop slack
> number of bio's.
> 
> The cache is intended to be per-task, and the user will need to supply
> the storage for it. As io_uring will be the only user right now, provide
> a hook that returns the cache there. Stub it out as NULL initially.

Is it possible for user space to submit & poll IO from different io_uring
tasks?

Then one bio may be allocated from bio cache of the submission task, and
freed to cache of the poll task?


Thanks, 
Ming