Re: ide-cs using 100% CPU

[Paulo Marques]

Hamie wrote:
> Alan Cox wrote:
>
> > On Gwe, 2004-08-06 at 20:33, Hamie wrote:
> >  
> >
> > > Is 100% CPU not excessive? IIRC my PIII-750 used to use less CPU 
> > > doing the same job as quick, or even slightly faster...
> > >   
> >
> >
> > PCMCIA IDE is PIO only so it burns CPU. This is one case where
> > hyperthreading is nice. Cardbus IDE is a lot better but very little
> > exists and we don't currently support hotplug IDE controllers.
> >
> >  
>
> Ah right. But would a CF memory card be cardbus anyway?

I've never seen a CF card that supported DMA (and I've worked with 
several brands). Compact Flash cards have several modes of operation and 
only one of this modes is "IDE-compatible".

> > > And should it not use system CPU rather than user CPU?
> > >   
> >
> >
> > Yes - but figure out please if the kernel or userspace is getting that
> > wrong ;)
> >
> >  
>
> My apologies. It was gkrellm leading me up the garden path on that 
> one... Copying about 100MB from a 512MB CF card (25+ photos from my 
> camera) vmstat 5 reports 4% usercpu, 96% system cpu. And the response on 
> the system is sluggish to say the least. (Moving the pointer in X is 
> painful :). gkrell meanwhile on it's cpu graph shows about 30% system, 
> and the rest as userCPU. No idea why, I guess till I find out I'll just 
> regard gkrellm's cpu graph as a waste of space (To differentiate system 
> & user cpu anyway :).

I think this is more of a scheduler/priorities problem. Maybe all the 
work that is being done with staircase / low-latency will help you on 
this :)

--
Paulo Marques - www.grupopie.com
"In a world without walls and fences who needs windows and gates?"
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