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: <3cccec37-ef58-cccb-7ab8-499ebfe133be@kernel.org>
Date:   Wed, 28 Sep 2022 13:31:37 -0600
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0)
 Gecko/20100101 Thunderbird/91.13.0
Subject: Re: [PATCH net-next v4 00/27] io_uring zerocopy send
Content-Language: en-US
To:     Pavel Begunkov <asml.silence@gmail.com>, io-uring@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Jonathan Lemon <jonathan.lemon@gmail.com>,
        Willem de Bruijn <willemb@google.com>,
        Jens Axboe <axboe@kernel.dk>, kernel-team@fb.com
References: <cover.1657194434.git.asml.silence@gmail.com>
 <2c49d634-bd8a-5a7f-0f66-65dba22bae0d@kernel.org>
 <bd9960ab-c9d8-8e5d-c347-8049cdf5708a@gmail.com>
 <0f54508f-e819-e367-84c2-7aa0d7767097@gmail.com>
 <d10f20a9-851a-33be-2615-a57ab92aca90@kernel.org>
 <bc48e2bb-37ee-5b7c-5a97-01e026de2ba4@gmail.com>
 <812c3233-1b64-8a0d-f820-26b98ff6642d@kernel.org>
 <3b81b3e1-2810-5125-f4a0-d6ba45c1fbd3@kernel.org>
 <24b050e0-433f-dc97-7aab-15c9175f49fa@gmail.com>
From:   David Ahern <dsahern@kernel.org>
In-Reply-To: <24b050e0-433f-dc97-7aab-15c9175f49fa@gmail.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Precedence: bulk

On 9/26/22 1:08 PM, Pavel Begunkov wrote:
> Tried it out, the branch below fixes a small problem, adds a couple
> of extra optimisations and now it actually uses registered buffers.
> 
>     https://github.com/isilence/iperf iou-sendzc

thanks for the patch; will it pull it in.

> 
> Still, the submission loop looked a bit weird, i.e. it submits I/O
> to io_uring only when it exhausts sqes instead of sending right
> away with some notion of QD and/or sending in batches. The approach
> is good for batching (SQ size =16 here), but not so for latency.
> 
> I also see some CPU cycles being burnt in select(2). io_uring wait
> would be more natural and perhaps more performant, but I didn't
> spend enough time with iperf to say for sure.

ok. It will be a while before I have time to come back to it. In the
meantime it seems like some io_uring changes happened between your dev
branch and what was merged into liburing (compile worked on your branch
but fails with upstream). Is the ZC support in liburing now?