Speeding up boot - an idea

[Adam Jackson]

On Tue, 2008-08-05 at 17:44 -0400, Chuck Ebbert wrote:
> Has anyone played with increasing the size of the disk queues?
> 
> /sys/block/<device>/queue/nr_requests is the maximum number of queued
> requests for the device -- the default is 128.

Testing on an oqo2, which just has a dumb (and brutally slow) PATA
drive, gives virtually identical bootcharts for queue depths of 128 and
1024:

http://ajax.fedorapeople.org/oqo-bootcharts/

The deeper queue does boot marginally faster, which could easily be
experimental noise.  It also appears to be very slightly more bound to
i/o wait (compare between 70 and 75 seconds on the two charts), which
could be noise or could be keeping the queue filled.  Tough to say.

Pretty sure this disk doesn't even have TCQ though.  Might be
interesting to try this on a competent disk.

- ajax
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