Moblin config kernel initialisation performance

Andy Whitcroft apw at canonical.com
Wed Dec 2 19:43:45 GMT 2009


One of our goals from UDS was to analyse the kernel initialisation
performance.  The moblin kernel was measured to initialise in about .9s
whereas the default Ubuntu kernel was booting in about 1.5s (both on the
10v).

While testing the async_populate_rootfs patches I noted did a little
experimentation to see what else was slowing boot and comparing the
configuration for those components to the moblin kernel.  The major costs
are populate_rootfs, pnpisa_init, piix_init and associated port probes.
We know that moblin does not use an initramfs, and as we can see below
isapnp is turned off in their config:

    config-generic:# CONFIG_ISAPNP is not set

If I boot my 10v with no initramfs and with isapnp disabled on the
command line I get a kernel init time of approximatly 0.8s.  In short
we can account in full for the kernel init performance difference from
disabling both the initramfs and isapnp.

-apw



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