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From: Dave Martin <Dave.Martin@arm.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: viro@zeniv.linux.org.uk, mtk.manpages@gmail.com,
	shuah@kernel.org, linux-api@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-man@vger.kernel.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH 0/3] readfile(2): a new syscall to make open/read/close faster
Date: Mon, 6 Jul 2020 18:25:41 +0100	[thread overview]
Message-ID: <20200706172541.GG10992@arm.com> (raw)
In-Reply-To: <20200704140250.423345-1-gregkh@linuxfoundation.org>

On Sat, Jul 04, 2020 at 04:02:46PM +0200, Greg Kroah-Hartman wrote:
> Here is a tiny new syscall, readfile, that makes it simpler to read
> small/medium sized files all in one shot, no need to do open/read/close.
> This is especially helpful for tools that poke around in procfs or
> sysfs, making a little bit of a less system load than before, especially
> as syscall overheads go up over time due to various CPU bugs being
> addressed.
> 
> There are 4 patches in this series, the first 3 are against the kernel
> tree, adding the syscall logic, wiring up the syscall, and adding some
> tests for it.
> 
> The last patch is agains the man-pages project, adding a tiny man page
> to try to describe the new syscall.

General question, using this series as an illustration only:


At the risk of starting a flamewar, why is this needed?  Is there a
realistic usecase that would get significant benefit from this?

A lot of syscalls seem to get added that combine or refactor the
functionality of existing syscalls without justifying why this is
needed (or even wise).  This case feels like a solution, not a
primitive, so I wonder if the long-term ABI fragmentation is worth the
benefit.

I ask because I'd like to get an idea of the policy on what is and is
not considered a frivolous ABI extension.

(I'm sure a usecase must be in mind, but it isn't mentioned here.
Certainly the time it takes top to dump the contents of /proc leaves
something to be desired.)

Cheers
---Dave

  parent reply	other threads:[~2020-07-06 17:25 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-04 14:02 Greg Kroah-Hartman
2020-07-04 14:02 ` [PATCH 1/3] readfile: implement readfile syscall Greg Kroah-Hartman
2020-07-04 18:35   ` Geert Uytterhoeven
2020-07-04 19:14   ` Matthew Wilcox
2020-07-04 19:41   ` Miklos Szeredi
2020-07-04 20:12     ` Al Viro
2020-07-04 20:16       ` Al Viro
2020-07-04 14:02 ` [PATCH 2/3] arch: wire up the " Greg Kroah-Hartman
2020-07-04 18:36   ` Geert Uytterhoeven
2020-07-04 14:02 ` [PATCH 3/3] selftests: add readfile(2) selftests Greg Kroah-Hartman
2020-07-04 18:38   ` Geert Uytterhoeven
2020-07-05  6:55     ` Greg Kroah-Hartman
2020-07-05 11:24       ` Geert Uytterhoeven
2020-07-05 11:36         ` Greg Kroah-Hartman
2020-07-05  1:41   ` Heinrich Schuchardt
2020-07-05  7:34     ` Greg Kroah-Hartman
2020-07-05  9:46       ` Heinrich Schuchardt
2020-07-04 14:02 ` [PATCH] readfile.2: new page describing readfile(2) Greg Kroah-Hartman
2020-07-05  2:54   ` Heinrich Schuchardt
2020-07-04 19:30 ` [PATCH 0/3] readfile(2): a new syscall to make open/read/close faster Al Viro
2020-07-05 11:47   ` Greg Kroah-Hartman
2020-07-06 17:25 ` Dave Martin [this message]
2020-07-05  2:06 Jan Ziak
2020-07-05  2:16 ` Matthew Wilcox
2020-07-05  2:46   ` Jan Ziak
2020-07-05  3:12     ` Matthew Wilcox
2020-07-05  3:18       ` Jan Ziak
2020-07-05  3:27         ` Matthew Wilcox
2020-07-05  4:09           ` Jan Ziak
2020-07-05 11:58             ` Greg KH
2020-07-06  6:07               ` Jan Ziak
2020-07-06 11:11                 ` Matthew Wilcox
2020-07-06 11:18                 ` Greg KH
2020-07-05  8:07           ` Vito Caputo
2020-07-05 11:44             ` Greg KH
2020-07-05 20:34               ` Vito Caputo
2020-07-05  6:32     ` Andreas Dilger
2020-07-05  7:25       ` Jan Ziak
2020-07-05 12:00         ` Greg KH
2020-07-05 11:50 ` Greg KH
2020-07-14  6:51   ` Pavel Machek
2020-07-14  8:07     ` Miklos Szeredi
2020-07-14 11:34       ` Pavel Begunkov
2020-07-14 11:55         ` Miklos Szeredi
2020-07-15  8:31           ` Pavel Begunkov
2020-07-15  8:41             ` Miklos Szeredi
2020-07-15  8:49               ` Pavel Begunkov
2020-07-15  9:00                 ` Pavel Begunkov
2020-07-15 11:17                   ` Miklos Szeredi

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