Received-SPF: pass (google.com: domain of linux-kernel+bounces-118344-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1;
Message-ID: <f7f547aa-998f-4e9f-89e1-1b10f83912d6@kernel.dk>
Date: Mon, 25 Mar 2024 21:39:25 -0600
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: io_uring: releasing CPU resources when polling
Content-Language: en-US
To: Xue <xue01.he@samsung.com>
Cc: asml.silence@gmail.com, linux-kernel@vger.kernel.org,
 io-uring@vger.kernel.org, peiwei.li@samsung.com, joshi.k@samsung.com,
 kundan.kumar@samsung.com, anuj20.g@samsung.com, wenwen.chen@samsung.com,
 ruyi.zhang@samsung.com, xiaobing.li@samsung.com, cliang01.li@samsung.com
References: <20240318090017.3959252-1-xue01.he@samsung.com>
 <CGME20240326032337epcas5p4d4725729834e3fdb006293d1aab4053d@epcas5p4.samsung.com>
 <20240326032331.1003213-1-xue01.he@samsung.com>
From: Jens Axboe <axboe@kernel.dk>
In-Reply-To: <20240326032331.1003213-1-xue01.he@samsung.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit

On 3/25/24 9:23 PM, Xue wrote:
> Hi,
> 
> I hope this message finds you well.
> 
> I'm waiting to follow up on the patch I submitted on 3.18,
> titled "io_uring: releasing CPU resources when polling".
> 
> I haven't received feedback yet and wondering if you had
> a chance to look at it. Any guidance or suggestions you could
> provide would be greatly appreciated.

I did take a look at it, and I have to be honest - I don't like it at
all. It's a lot of expensive code in the fast path, for a problem that
should not really exist. The system is misconfigured if you're doing
polled IO for devices that don't have a poll queue. At some point the
block layer returned -EOPNOTSUPP for that, and honestly I think that's a
MUCH better solution than adding expensive code in the fast path for
something that is really a badly configured setup.

-- 
Jens Axboe