Re: [PATCH 0/4] Fastboot revisited: Asynchronous function calls

Arjan van de Ven
2009-01-04T18:31:04Z

On Sun, 4 Jan 2009 10:16:57 -0800 (PST)
Linus Torvalds <torvalds@linux-foundation.org> wrote:

>
>
> On Sun, 4 Jan 2009, Arjan van de Ven wrote:
> >
> > To see this working, I uploaded a "before" and "after" kernel
> > bootchart for one of my testboxes at
> >
> > http://www.fenrus.org/linux/before.svg
> > http://www.fenrus.org/linux/after.svg
>
> Ok, so why does the serial port init take so long? That's a quarter
> of a second for you, which is ridiculous.

good question; I was about to start looking into that one (but wanted
to get the patches out first before I did more than 3 to not waste time
on some dead-end approach if it ends up being that)

>
> I _think_ it's the irq auto-probing, but that's just a guess.

I kinda was hoping that in part it was a scaling thing with the number
of ports (4 in my .config) so that I could do the ports
asynchronous compared to eachother ;-)

> The irq auto-probing itself also has a few excessive delays, like
> waiting for 0.1 s just to wait for spurious interrupts to trigger.
> Doing the extra unnecessary probe makes that doubly expensive.
>
> Does this patch make any difference to you? I'm not at all sure that
> it's the irq probing, but if it is, then this should make the serial
> probe go much faster.

it turned it into a 25 msec deal .. pretty good improvement in my book.
(now I still might want to try to do this async so that it becomes
25/4 ... but the pressure i

--
Arjan van de Ven Intel Open Source Technology Centre
For development, discussion and tips for power savings,
visit http://www.lesswatts.org