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Re: [Xen-devel] RE: rdtsc: correctness vs performance on Xen (and KVM?)
| To: | Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>, Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] RE: rdtsc: correctness vs performance on Xen (and KVM?) |
| From: | Keir Fraser <keir.fraser@xxxxxxxxxxxxx> |
| Date: | Tue, 01 Sep 2009 17:06:00 +0100 |
| Cc: | "Xen-Devel \(E-mail\)" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> |
| Delivery-date: | Tue, 01 Sep 2009 09:06:42 -0700 |
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| Thread-topic: | [Xen-devel] RE: rdtsc: correctness vs performance on Xen (and KVM?) |
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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 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
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