Re: [RFC][PATCH] nameing reserved pages [0/3]

[Arjan van de Ven]

On Wed, 2005-04-20 at 23:15 +0900, Kamezawa Hiroyuki wrote:
> Arjan van de Ven wrote:
> 
> >>For example, Memory Hotplug can ignore (a).
> >>    
> >>
> >
> >Memory Hotplug can also use page_is_ram().
> >  
> >
> Yes. we can use page_is_ram() for finding (a)memory hole.
> But I'd like to catch other removable PG_reserved pages like (d)Isorated 
> by MCA (e)used by perfmon and
> some of (b) used by kernerl and (c) Set by drivers.
> What I'm thinking of is to detect whether memory is hot-removable or not 
> before removing actually.

MCA's probably shouldn't set PG_reserved; I don't see why they should.
They could just steal the page and "leak" it.

> 
> >/dev/memstate really looks like a bad idea to me as well... I rather
> >have less than more /dev/*mem*
> >  
> >
> For showing page usage and its "location", I've thought of other 
> interface, sysfs, procfs...
> But I have no idea.

Why do you want this exported to userspace? There is absolutely no way
you can get this exported race free without shutting the VM down, and
without being race free this information has absolutely no meaning !!
(and when you shut the VM down you really shouldn't depend on userspace
anymore either)



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