Re: [Xen-devel] RE: rdtsc: correctness vs performance on Xen (and KVM?)

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 01/09/2009 16:56, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

>> Not within today's Xen or Linux (which both assume a global kernel
>> address space, in particular non-root page table entries
>> mapping kernel
>> space to be the same in all address spaces - you'd need
>> separate entries
>> at all levels for this).
> 
> OK, I forgot: No software-accessible TLB.
> 
> Can you think of any trick (that doesn't require the cost of a
> trap/hypercall) to allow an app to determine what pcpu
> it is running on?

I can't think of any that don't require kernel modifications. Which takes us
back to considering vsyscall, perhaps.

 -- Keir



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