linux-kernel - Re: [RFC PATCH 00/13] x86 User Interrupts support

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Message-ID: <ecf3cf2e-685d-afb9-1a5d-1382714cc60c@kernel.dk>
Date:   Thu, 23 Sep 2021 08:39:30 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Sohil Mehta <sohil.mehta@...el.com>, x86@...nel.org
Cc:     Tony Luck <tony.luck@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Christian Brauner <christian@...uner.io>,
        Peter Zijlstra <peterz@...radead.org>,
        Shuah Khan <shuah@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Ashok Raj <ashok.raj@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Gayatri Kammela <gayatri.kammela@...el.com>,
        Zeng Guang <guang.zeng@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Randy E Witt <randy.e.witt@...el.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        Ramesh Thomas <ramesh.thomas@...el.com>,
        linux-api@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [RFC PATCH 00/13] x86 User Interrupts support

On 9/13/21 2:01 PM, Sohil Mehta wrote:
> - Discuss potential use cases.
> We are starting to look at actual usages and libraries (like libevent[2] and
> liburing[3]) that can take advantage of this technology. Unfortunately, we
> don't have much to share on this right now. We need some help from the
> community to identify usages that can benefit from this. We would like to make
> sure the proposed APIs work for the eventual consumers.

One use case for liburing/io_uring would be to use it instead of eventfd
for notifications. I know some folks do use eventfd right now, though
it's not that common. But if we had support for something like this,
then you could use it to know when to reap events rather than sleep in
the kernel. Or at least to be notified when new events have been posted
to the cq ring.

-- 
Jens Axboe