Re: [PATCH 0/3] readfile(2): a new syscall to make open/read/close faster

From: Pavel Begunkov <asml.silence@gmail.com>
To: Miklos Szeredi <miklos@szeredi.hu>, Pavel Machek <pavel@denx.de>
Cc: Greg KH <gregkh@linuxfoundation.org>,
	Jan Ziak <0xe2.0x9a.0x9b@gmail.com>,
	Linux API <linux-api@vger.kernel.org>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-kselftest@vger.kernel.org,
	linux-man <linux-man@vger.kernel.org>,
	Michael Kerrisk <mtk.manpages@gmail.com>,
	shuah@kernel.org, Al Viro <viro@zeniv.linux.org.uk>,
	io-uring@vger.kernel.org
Subject: Re: [PATCH 0/3] readfile(2): a new syscall to make open/read/close faster
Date: Tue, 14 Jul 2020 14:34:30 +0300	[thread overview]
Message-ID: <4e92b851-ce9a-e2f6-3f9a-a4d47219d320@gmail.com> (raw)
In-Reply-To: <CAJfpegu8AXZWQh3W39PriqxVna+t3D2pz23t_4xEVxGcNf1AUA@mail.gmail.com>

On 14/07/2020 11:07, Miklos Szeredi wrote:
> On Tue, Jul 14, 2020 at 8:51 AM Pavel Machek <pavel@denx.de> wrote:
>>
>> Hi!
>>
>>>> At first, I thought that the proposed system call is capable of
>>>> reading *multiple* small files using a single system call - which
>>>> would help increase HDD/SSD queue utilization and increase IOPS (I/O
>>>> operations per second) - but that isn't the case and the proposed
>>>> system call can read just a single file.
>>>
>>> If you want to do this for multple files, use io_ring, that's what it
>>> was designed for.  I think Jens was going to be adding support for the
>>> open/read/close pattern to it as well, after some other more pressing
>>> features/fixes were finished.
>>
>> What about... just using io_uring for single file, too? I'm pretty
>> sure it can be wrapped in a library that is simple to use, avoiding
>> need for new syscall.
> 
> Just wondering:  is there a plan to add strace support to io_uring?
> And I don't just mean the syscalls associated with io_uring, but
> tracing the ring itself.

What kind of support do you mean? io_uring is asynchronous in nature
with all intrinsic tracing/debugging/etc. problems of such APIs.
And there are a lot of handy trace points, are those not enough?

Though, this can be an interesting project to rethink how async
APIs are worked with.

> 
> I think that's quite important as io_uring becomes mainstream.

-- 
Pavel Begunkov