Re: [PATCH 1/1] SGI X86 UV: Provide a System Activity Indicatordriver

From: Pavel Machek
Date: Tue Sep 30 2008 - 19:39:10 EST



> Another relevant point is that I will be adding a bit more functionality
> to disable the timer interrupt on truly "idle" cpus (like have been idle
> for some amount of seconds). We would then use the "exit from idle"
> callback to reestablish the timer interrupt. [This would allow them to
> enter power down states if appropriate.]

Should you look at nohz instead of reinventing it?

> > As i suggested in my previous mail about this topic, a low-frequency
> > sampling method should be used instead, to indicate system status. I
> > thought the leds drivers have all that in place already.
>
> It is low frequency (once per second), this is just setting what's to
> be sampled.
>
> As I mentioned, this is not for LED displays (human readable), it's for the
> system controller to monitor how all parts of the system are running, and
> this one is just the cpu parts. The LED driver approach would have me
> registering 4096 led devices, with all their callbacks, 4096 strings saying
> "LED0001", etc., and I still cannot associate a specific register bit
> (AKA LED if that's what it was), with a specific cpu using the LED driver.
>
> The LED driver is fine for a couple of blinking lights indicating overall
> system activity, disk activity, etc. (Btw, I did not see a network trigger,
> or a paging trigger, or an out of memory trigger, or some other things that
> might be useful for real time monitoring of the system.)

...so add them...

> But the LED driver has way more overhead than needed for this simple application.
>

So overhead from led driver is not okay, while overhead from messing
with idle loop is okay? Interesting...
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/