Re: [OLPC-devel] Re: [RFC][PATCH 1/2] ACPI: Idle Processor PM Improvements

[Pavel Machek <pavel@ucw.cz>]

Hi!

> In short, we have novel hardware: we can have our screen on, and suspend
> the processor to RAM, and use a half a watt.  We can have our wireless
> forwarding packets in our mesh networks, with the processor suspended,
> consuming under 400mw (we hope 300mw by the time we ship).  Both on, and
> we're still under one watt.
> 
> For keyboard activity, human perception is in the 100-200 millisecond
> range; for some other stuff, it is even less much than that.  So that's
> the necessity; now the invention.
> 
> I've done a straw pole among kernel gurus at OLS and elsewhere on how
> fast Linux might be able to resume. I've gotten answers of typically
> "one second".
> 
> But, on other platforms (see attached), I have data I've measured myself
> showing Linux going from resume from RAM to *scheduling user level
> processes* 100 times faster than that, on a wimpy 200mhz ARM processor.
> Yes, Matilda, Linux can, on non-braindead hardware, resume all the way
> to scheduling user processes in 10 milliseconds on a 200mhz processor.

2.4 and 2.6 are *very* different here. You'll probably need to optimize freezer
in 2.6 a bit...
							Pavel
-- 
Thanks for all the (sleeping) penguins.