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

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

On 14/07/2020 11:07, Miklos Szeredi wrote:
> On Tue, Jul 14, 2020 at 8:51 AM Pavel Machek <pavel@...x.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