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Message-Id: <20090326171148.9bf8f1ec.akpm@linux-foundation.org>
Date: Thu, 26 Mar 2009 17:11:48 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Theodore Tso <tytso@....edu>, David Rees <drees76@...il.com>,
Jesper Krogh <jesper@...gh.cc>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Linux 2.6.29
On Wed, 25 Mar 2009 16:23:08 -0700 (PDT) Linus Torvalds <torvalds@...ux-foundation.org> wrote:
>
>
> On Wed, 25 Mar 2009, Theodore Tso wrote:
> > >
> > > The problem being that unlike the ratio, there's no sane default value
> > > that you can at least argue is not _entirely_ pointless.
> >
> > Well, if the maximum time that someone wants to wait for an fsync() to
> > return is one second, and the RAID array can write 100MB/sec
>
> How are you going to tell the kernel that the RAID array can write
> 100MB/s?
>
> The kernel has no idea.
>
userspace can do it quite easily. Run a self-tuning script after
installation and when the disk hardware changes significantly.
It is very disappointing that nobody appears to have attempted to do
_any_ sensible tuning of these controls in all this time - we just keep
thrashing around trying to pick better magic numbers in the base kernel.
Maybe we should set the tunables to 99.9% to make it suck enough to
motivate someone.
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