On Wed, Jan 27, 2010 at 11:34:54AM -0800, Jeremy Fitzhardinge wrote:
> On 01/27/2010 11:18 AM, Ian Campbell wrote:
>>> That's a thought. It could be generally useful too; highpte should only
>>> be used in extreme circumstances (to prevent ptes from filling most of
>>> lowmem), not on every system with highmem. IOW use a generic flag
>>> rather than make it explicitly Xen-related, then we can set that flag.
>>> 
>> I think this is the most plausible idea. Need to think about what
>> criteria would be used to set the flag on native, simply raw RAM size?
>> i.e. you wouldn't use HIGHPTE on a 4G system, even if CONFIG_HIGHPTE is
>> enabled, but where would the cut-off be?
>>
>> Rather than a flag I guess I'd make a pte_gfp variable which could be
>> modified to suit.
>> 
>
> Well, you could try heuristicing it up, but I suspect a simpler approach 
> is just a variable which is enabled by command line and/or config 
> option. HIGHPTE is an arch-independent concept, but the policy for 
> defaulting it is arch-specific; on x86 it should almost always be off.
>
>>> Or we could just put a big fat config dependency in.
>>> 
>> I'd imagine that seemingly random "depends !XEN" would be unpopular
>> upstream.
>> 
>
> I was thinking the other way around; Xen depends on !HIGHPTE. But a 
> runtime switch would be just as good.
>
Maybe a stupid question, but how is this stuff handled in linux-2.6.18-xen ?
-- Pasi
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