linux-kernel - Re: [PATCH] io_uring: wakeup threads waiting for EPOLLOUT events

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Message-ID: <a02a58dc-bf23-ed74-aec6-52c85360fe00@kernel.dk>
Date:   Thu, 16 Jan 2020 09:30:12 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] io_uring: wakeup threads waiting for EPOLLOUT events

On 1/16/20 9:26 AM, Stefano Garzarella wrote:
>> Since the use case is mostly single submitter, unless you're doing
>> something funky or unusual, you're not going to be needing POLLOUT ever.
> 
> The case that I had in mind was with kernel side polling enabled and
> a single submitter that can use epoll() to wait free slots in the SQ
> ring. (I don't have a test, maybe I can write one...)

Right, I think that's the only use case where it makes sense, because
you have someone else draining the sq side for you. A test case would
indeed be nice, liburing has a good arsenal of test cases and this would
be a good addition!

-- 
Jens Axboe