Subject: Re: [PATCH] x86:
	fix	unconditional	arch/x86/kernel/pcspeaker.c?compiling
From: Matt Mackall <mpm@selenic.com>
To: Rob Landley <rob@landley.net>
Cc: linux-tiny@selenic.com,
       Michael Opdenacker <michael-lists@free-electrons.com>,
       Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
       linux-kernel@vger.kernel.org
In-Reply-To: <200801192259.47063.rob@landley.net>
References: <200801171643.49301.michael-lists@free-electrons.com>
	 <4790D3E3.4060409@free-electrons.com>
	 <1200676219.3835.8.camel@cinder.waste.org>
	 <200801192259.47063.rob@landley.net>
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Date: Sun, 20 Jan 2008 10:44:48 -0600
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On Sat, 2008-01-19 at 22:59 -0600, Rob Landley wrote:
> On Friday 18 January 2008 11:10:19 Matt Mackall wrote:
> > >     * Disable support for readahead, page writeback, pdflush and swap
> > >       when we have no storage at all (typically booting from an
> > >       initramfs). This corresponds to 69 KB of source code!
> >
> > That'd be nice, yes. It would probably make sense to be able to disable
> > just readahead support when we're working with only solid-state devices.
> 
> Very nice.  From a UI standpoint, shouldn't disabling the block layer take at 
> least some of that out?

There are a number of laptops now that ship with solid-state disks.
These things look like normal IDE block devices to the kernel, but have
zero seek time and zero rotational latency. So here, prefetch is a waste
of memory and probably increases latency on average.

This will also be true for using prefetch on a typical embedded board
using compact flash through an IDE interface controller (extremely
common).

-- 
Mathematics is the supreme nostalgia of our time.

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