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

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Date:   Sun, 5 Jul 2020 13:47:06 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     mtk.manpages@...il.com, shuah@...nel.org,
        linux-api@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-man@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 0/3] readfile(2): a new syscall to make open/read/close
 faster

On Sat, Jul 04, 2020 at 08:30:40PM +0100, Al Viro wrote:
> 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.
> 
> Nice series, but you are 3 months late with it...  Next AFD, perhaps?

Perhaps :)

> Seriously, the rationale is bollocks.  If the overhead of 2 extra
> syscalls is anywhere near the costs of the real work being done by
> that thing, we have already lost and the best thing to do is to
> throw the system away and start with saner hardware.

The real-work the kernel does is almost neglegant compared to the
open/close overhead of the syscalls on some platforms today.  I'll post
benchmarks with the next version of this patch series to hopefully show
that.  If not, then yeah, this isn't worth it, but it was fun to write.

thanks,

greg k-h