Re: [PATCH for-next 0/8] io_uring: multishot recv

[Jens Axboe <axboe@kernel.dk>]

On 6/28/22 9:02 AM, Dylan Yudaken wrote:
> This series adds support for multishot recv/recvmsg to io_uring.
> 
> The idea is that generally socket applications will be continually
> enqueuing a new recv() when the previous one completes. This can be
> improved on by allowing the application to queue a multishot receive,
> which will post completions as and when data is available. It uses the
> provided buffers feature to receive new data into a pool provided by
> the application.
> 
> This is more performant in a few ways:
> * Subsequent receives are queued up straight away without requiring the
>   application to finish a processing loop.
> * If there are more data in the socket (sat the provided buffer
>   size is smaller than the socket buffer) then the data is immediately
>   returned, improving batching.
> *  Poll is only armed once and reused, saving CPU cycles

The latter is really a big deal, it saves a substantial amount of wait
queue locking and manipulation.

In general this looks good to me. I agree on allowing length of 0, we
strictly don't need a length as that is implicit from the provided
buffer anyway (and capped by that, ultimately). Nice cleanups leading
into the real change too.

Added some individual comments on select patches.

-- 
Jens Axboe