Re: [PATCHSET v2 RFC 0/11] Add support for ring mapped provided buffers

[Jens Axboe <axboe@kernel.dk>]

On 5/1/22 7:14 AM, Pavel Begunkov wrote:
> On 4/29/22 18:56, Jens Axboe wrote:
>> Hi,
>>
>> This series builds to adding support for a different way of doing
>> provided buffers. The interesting bits here are patch 11, which also has
>> some performance numbers an an explanation of it.
> 
> Jens, would be great if you can CC me for large changes, you know
> how it's with mailing lists nowadays...

You bet, I can just add you to anything posted. Starting to lose faith
in email ever becoming reliable again...

> 1) reading "io_uring: abstract out provided buffer list selection"
> 
> Let's move io_ring_submit_unlock() to where the lock call is.
> In the end, it's only confusing and duplicates unlock in
> io_ring_buffer_select() and io_provided_buffer_select().

Sure, I can clean that up.

> 2) As it's a new API, let's do bucket selection right, I quite
> don't like io_buffer_get_list(). We can replace "bgid" with
> indexes into an array and let the userspace to handle indexing.
> Most likely it knows the index right away or can implement indexes
> lookup with as many tricks and caching it needs.

Maybe we can just use xarray here rather than a hashed list? It's really
just a sparse array. The downside is that xarray locking isn't always
very convenient, eg using it with your own locking...

Any other suggestions?

-- 
Jens Axboe