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Re: Speed up the boot by loading the kernel disk cache

[Petter Reinholdtsen]
> Today a new package to speed up the boot is available in unstable.
> The readahead binary package can speed up the boot quite significantly
> by optimizing how the hard drive is used.  It make sure the kernel
> disk cache is populated as the very first thing done at boot with the
> files used during boot.  To test it, install readahead, boot once with
> 'profile' as a kernel option to tune it to your boot, and then boot
> normally.

Should we include this feature in the default installation for lenny?
I know some work is going on to make a more dynamic solution,
<URL:https://wiki.ubuntu.com/DesktopTeam/Specs/Prefetch>, but while we
wait for that to stabilize, I believe the readahead solution improve
the boot times quite a lot.  If we also manage to switch to dash as
the default /bin/sh, the impact should be significant.

The readahead package made it into testing today, so it is available
for a larger number of testers.  Currently only 0.1% of the population
have it installed.

> It should not be used with preload (or at least, the profiling
> should never be done when preload is enabled), as it will make
> readahead believe that all the files loaded by preload are used
> during boot, and thus waste time and kernel disk cache on files only
> needed after the boot.

I'll try to find a way to avoid this problem with the interaction with
the preload package.  One idea is to make sure preload start after the
readahead-watch program is stopped.

> I welcome benchmarks on the initscripts-ng-devel mailing list,
> <URL:http://lists.alioth.debian.org/mailman/listinfo/initscripts-ng-devel>.

Very much so. :)

The ones I have seen so far reported of 10% speedup, and one report on
slowdown.  Not quite sure what is the problem with the one reporting a
slowdown.  To benchmark, use the bootchart package, and boot with

Happy hacking,
Petter Reinholdtsen

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