On Tue, May 29, 2007 at 09:47:53AM +0800, Yang Sheng wrote:
> On Tuesday 29 May 2007 06:52, Randy Dunlap wrote:
> > On Mon, 28 May 2007 15:03:10 +0800 Yang Sheng wrote:
> > > Why we need this:
> > >
> > > It can speed up the calling of initcalls, especially useful for some
> > > embed device.
> >
> > Can you give concrete example(s) of why we need this?
> > Any real configs/hardware where it helps and how much it helps.
> >
>
> We didn't got the precise data at hand now, because we should build a complete
> stable initcall dependence relationship for it, but we can't do it now.
>
> But we have done a relative stable test in a common x86_64 machine, with 2
> threads and one dependence relation(pnpacpi_init depends on pnp_init and
> acpi_init). The result is the time spending on initcall calling reducing from
> about _5s_ to _2s_ (make the kernel with the defconfig). We analyzed the
> dmesg and found the most of time was save by run ide_generic_init and
> piix_init in parallel.
>
> Of course the dependence in the test case is not sufficient, but the effect is
> shown.
>
> We think this patch would be very useful in some embed deviced which requires
> fast boot speed. Some server may benefit too because of it's long time for
> device initiation.
If we decide to do this, we should also introduce a way to disable it
at runtime with initcall=noparallel or something. Why?
Because right now when people say "my computer hangs during bootup"
we can ask them to boot with initcall_debug and usually find out
the last thing it did before it locked up. If we parallelise this,
the output will be a lot harder to decipher.
Dave
--
http://www.codemonkey.org.uk
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