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Date: Thu, 26 Mar 2009 10:46:04 +1100
From: Bron Gondwana <brong@fastmail.fm>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Theodore Tso <tytso@mit.edu>, David Rees <drees76@gmail.com>,
       Jesper Krogh <jesper@krogh.cc>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Linux 2.6.29
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On Wed, Mar 25, 2009 at 04:23:08PM -0700, Linus Torvalds 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.

Not at boot up, but after it's been using the RAID array for a little
while it could...

Bron (... imagining a tunable "max_fsync_wait_target_centisecs = 100" 
      which caused the kernel to notice how long flushes were taking
      and tune its buffer sizes to be approximately right over time )