linux-kernel - Re: [RFC] sleepy linux

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Message-ID: <20080108191519.GA1690@elf.ucw.cz>
Date:	Tue, 8 Jan 2008 20:15:20 +0100
From:	Pavel Machek <pavel@....cz>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	kernel list <linux-kernel@...r.kernel.org>,
	Linux-pm mailing list <linux-pm@...ts.osdl.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [RFC] sleepy linux

Hi!
> 
> > > a quick feature request: could you please make the wake-on-RTC 
> > > capability generic and add a CONFIG_DEBUG_SUSPEND_ON_RAM=y config 
> > > option (disabled by default) that does a short 1-second 
> > > suspend-to-RAM sequence upon bootup? That way we could test s2ram 
> > > automatically (which is a MUCH needed feature for automated 
> > > regression testing and automatic bisection). In addition, some sort 
> > > of 'suspend for N seconds' /sys or /dev/rtc capability would be nice 
> > > as well.
> > 
> > Hmm, are you sure it is good idea to do this from kernel? I guess this 
> > is better done from script...
> 
> i have this low-prio effort to make all self-checks automatically 
> available via 'make randconfig' as well, for all features that have no 
> natural exposure during normal bootup. So far we've got rcutorture, 
> kprobes-check, locking/lockdep-self-test and a handful of others. 
> External scripts tend to go out of sync and LTP takes way too much time 
> to finish.

Well, I can give you a three liner, and if it stops working, I'll
treat is as a regression, because userland ABI changed...?

Or you can get about 10 lines of C, no problem, but I do not think
that should be merged to Linus.

> > > btw., how far are you from having a working prototype?
> > 
> > SCSI/SATA issues stop me just now, but even if I get that to work, it 
> > will be extremely disgusting hack... and it is unclear how to do it 
> > nicely :-(.
> 
> as long as the sleep periods are within say 10-20 seconds, and our s2ram 
> cycle is fast and optimal enough, we could do this with networking 
> enabled too, without dropping/stalling TCP connections left and
> right.

I do not think TCP would survive "10 seconds sleep, 1 second up". But...

> (Perhaps if we could notify routers that they should batch packets for N 
> seconds and we could turn off PHY during that time, it would be even 
> nicer - is there any such router extension in existence?)

...yes, we should probably play with the routers.

> but if it's nothing else but a s2ram debug/stress utility, that alone 
> would be great too :-)

 I expect to stress s2ram way too much ;-).
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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