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From: Miklos Szeredi <miklos@szeredi.hu>
To: Pavel Begunkov <asml.silence@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>,
	Andy Lutomirski <luto@amacapital.net>,
	Stefano Garzarella <sgarzare@redhat.com>,
	Kees Cook <keescook@chromium.org>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	strace-devel@lists.strace.io, io-uring@vger.kernel.org,
	Linux API <linux-api@vger.kernel.org>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: strace of io_uring events?
Date: Wed, 15 Jul 2020 22:09:54 +0200	[thread overview]
Message-ID: <CAJfpegt9=p4uo5U2GXqc-rwqOESzZCWAkGMRTY1r8H6fuXx96g@mail.gmail.com> (raw)
In-Reply-To: <7c09f6af-653f-db3f-2378-02dca2bc07f7@gmail.com>

On Wed, Jul 15, 2020 at 9:43 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
>
> To clear details for those who are not familiar with io_uring:
>
> io_uring has a pair of queues, submission (SQ) and completion queues (CQ),
> both shared between kernel and user spaces. The userspace submits requests
> by filling a chunk of memory in SQ. The kernel picks up SQ entries in
> (syscall io_uring_enter) or asynchronously by polling SQ.
>
> CQ entries are filled by the kernel completely asynchronously and
> in parallel. Some users just poll CQ to get them, but also have a way
> to wait for them.
>
> >>>
> >>> What do people think?
> >>>
> >>> From what I can tell, listing the submitted requests on
> >>> io_uring_enter() would not be hard.  Request completion is
> >>> asynchronous, however, and may not require  io_uring_enter() syscall.
> >>> Am I correct?
>
> Both, submission and completion sides may not require a syscall.

Okay.

> >>> Is there some existing tracing infrastructure that strace could use to
> >>> get async completion events?  Should we be introducing one?
>
> There are static trace points covering all needs.

This needs to be unprivileged, or its usefulness is again compromized.

>
> And if not used the whole thing have to be zero-overhead. Otherwise
> there is perf, which is zero-overhead, and this IMHO won't fly.

Obviously it needs to be zero overhead if not tracing.

What won't fly?

Thanks,
Miklos

  reply	other threads:[~2020-07-15 20:10 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-15 11:12 Miklos Szeredi
2020-07-15 14:35 ` Andy Lutomirski
2020-07-15 17:11   ` Matthew Wilcox
2020-07-15 19:42     ` Pavel Begunkov
2020-07-15 20:09       ` Miklos Szeredi [this message]
2020-07-15 20:20         ` Pavel Begunkov
2020-07-15 23:07           ` Kees Cook
2020-07-16 13:14             ` Stefano Garzarella
2020-07-16 15:12               ` Kees Cook
2020-07-17  8:01                 ` Stefano Garzarella
2020-07-21 15:27                   ` Andy Lutomirski
2020-07-21 15:31                     ` Jens Axboe
2020-07-21 17:23                       ` Andy Lutomirski
2020-07-21 17:30                         ` Jens Axboe
2020-07-21 17:44                           ` Andy Lutomirski
2020-07-21 18:39                             ` Jens Axboe
2020-07-21 19:44                               ` Andy Lutomirski
2020-07-21 19:48                                 ` Jens Axboe
2020-07-21 19:56                                 ` Andres Freund
2020-07-21 19:37                         ` Andres Freund
2020-07-21 15:58                     ` Stefano Garzarella
2020-07-23 10:39                       ` Stefan Hajnoczi
2020-07-23 13:37                       ` Colin Walters
2020-07-24  7:25                         ` Stefano Garzarella
2020-07-16 13:17             ` Aleksa Sarai
2020-07-16 15:19               ` Kees Cook
2020-07-17  8:17               ` Cyril Hrubis
2020-07-16 16:24             ` Andy Lutomirski
2020-07-16  0:12     ` tytso

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