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Re: [Xen-devel] Xen 4.3 development update

At 11:47 -0500 on 02 Apr (1364903259), Suravee Suthikulpanit wrote:
> On 4/2/2013 11:34 AM, Tim Deegan wrote:
> >At 16:42 +0100 on 02 Apr (1364920927), Jan Beulich wrote:
> >>>>>On 02.04.13 at 16:07, George Dunlap <George.Dunlap@xxxxxxxxxxxxx> 
> >>>>>wrote:
> >>>* AMD NPT performance regression after c/s 24770:7f79475d3de7
> >>>   owner: ?
> >>>   Reference: http://marc.info/?l=xen-devel&m=135075376805215
> >>This is supposedly fixed with the RTC changes Tim committed the
> >>other day. Suravee, is that correct?
> >This is a separate problem.  IIRC the AMD XP perf issue is caused by the
> >emulation of LAPIC TPR accesses slowing down with Andres's p2m locking
> >patches.  XP doesn't have 'lazy IRQL' or support for CR8, so it takes a
> >_lot_ of vmexits for IRQL reads and writes.
> Is this only for 32-bit XP? or also 64-bit ?

I don't have a 64-bit XP image handy to test, but a bit of googling
suggests that 64-bit XP has 'lazy IRQL', so this TPR problem should only
affect 32-bit XP (and earlier Windowses).


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