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

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Message-ID: <20200116155557.mwjc7vu33xespiag@steredhat>
Date:   Thu, 16 Jan 2020 16:55:57 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>
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 Thu, Jan 16, 2020 at 08:29:07AM -0700, Jens Axboe wrote:
> On 1/16/20 6:49 AM, Stefano Garzarella wrote:
> > io_uring_poll() sets EPOLLOUT flag if there is space in the
> > SQ ring, then we should wakeup threads waiting for EPOLLOUT
> > events when we expose the new SQ head to the userspace.
> > 
> > Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
> > ---
> > 
> > Do you think is better to change the name of 'cq_wait' and 'cq_fasync'?
> 
> I honestly think it'd be better to have separate waits for in/out poll,
> the below patch will introduce some unfortunate cacheline traffic
> between the submitter and completer side.

Agree, make sense. I'll send a v2 with a new 'sq_wait'.

About fasync, do you think could be useful the POLL_OUT support?
In this case, maybe is not simple to have two separate fasync_struct,
do you have any advice?

Thanks,
Stefano