Speeding up live cd boot through optimizing file layout

[Krzysztof Lichota]

Matt Zimmerman napisał(a):
> On Thu, Jun 08, 2006 at 08:03:05AM +0200, Krzysztof Lichota wrote:
>> Matt Zimmerman napisał(a):
>>> How interesting.  Did you ensure that the list is up to date?  If it is, it
>>> should be ordered according to the actual order in which files are read at
>>> boot, so there should be no other I/O happening in parallel to cause
>>> additional seeks.  Does the system have enough memory to cache all of the
>>> files there?
>> The list was up to date, I have always used the same RC iso image.
> 
> Don't assume that it's perfect; hard disks are much more forgiving in this
> respect than CDs.

I don't understand. What hard disk? I meant the list created by my
tracing facility in SquashFS and list of readahead files as present in
ISO image.

>> Maybe pinning readahead files in memory would help, but it is not that
>> simple to do and it might be risky (use memory which is not needed thus
>> making less memory available to apps).
> 
> I think block-level readahead might work better, since probably only a
> relatively small portion of each file is accessed during startup.

This can be done as SquashFS can print block numbers or my tracing
facility can be extended to print offset in file.

Unfortunately block-level layout cannot be done as SquashFS uses
continuous file allocation :)

	Krzysztof Lichota


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