Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <c1cb95f8-66be-e929-c26c-74d27e4ec498@kernel.dk>
Date:   Tue, 28 Jun 2022 09:19:03 -0600
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:91.0) Gecko/20100101
 Thunderbird/91.10.0
Subject: Re: [PATCH for-next 0/8] io_uring: multishot recv
Content-Language: en-US
To:     Dylan Yudaken <dylany@fb.com>,
        Pavel Begunkov <asml.silence@gmail.com>,
        io-uring@vger.kernel.org
Cc:     Kernel-team@fb.com, linux-kernel@vger.kernel.org
References: <20220628150228.1379645-1-dylany@fb.com>
From:   Jens Axboe <axboe@kernel.dk>
In-Reply-To: <20220628150228.1379645-1-dylany@fb.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

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