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Re: [Xen-devel] Load increase after memory upgrade (part2)

On Tue, Jan 17, 2012 at 04:02:25PM -0500, Konrad Rzeszutek Wilk wrote:
> > 
> > And the devices do work ... so how does that work ...
> Most (all?) drivers are written to work with bounce-buffering.
> That has never been a problem.
> The issue as I understand is that the DVB drivers allocate their buffers
> from 0->4GB most (all the time?) so they never have to do bounce-buffering.
> While the pv-ops one ends up quite frequently doing the bounce-buffering, 
> which
> implies that the DVB drivers end up allocating their buffers above the 4GB.
> This means we end up spending some CPU time (in the guest) copying the memory
> from >4GB to 0-4GB region (And vice-versa).
> And I am not clear why this is happening. Hence my thought
> was to run an Xen-O-Linux kernel v2.6.3X and a PVOPS v2.6.3X (where X is the
> same) with the same PCI device (and the test would entail rebooting the
> box in between the launches) to confirm that the Xen-O-Linux is doing 
> something
> that the PVOPS is not.
> So far, I've haven't had much luck compiling a Xen-O-Linux v2.6.38 kernel
> so :-(

Did you try downloading a binary rpm (or src.rpm) from OpenSuse? 
I think they have 2.6.38 xenlinux kernel available.

-- Pasi

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