[Xen-devel] Re: performance regression from c/s 21647:cfba1560054a

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 10 Nov 2011, Jan Beulich wrote:
> >>> On 10.11.11 at 16:16, Stefano Stabellini 
> >>> <stefano.stabellini@xxxxxxxxxxxxx>
> wrote:
> > On Thu, 10 Nov 2011, Jan Beulich wrote:
> >> >>> On 10.11.11 at 15:59, Stefano Stabellini 
> >> >>> <stefano.stabellini@xxxxxxxxxxxxx>
> >> wrote:
> >> > On Thu, 10 Nov 2011, Jan Beulich wrote:
> >> >> It's SLE11 SP1 guests that suffered a regression after a maintenance
> >> >> update (originally shipped with 4.0.0, while that patch got backported
> >> >> later into 4.0.x).
> >> > 
> >> > Is SLES11 SP1 using HVMOP_pagetable_dying (see
> >> > arch/x86/xen/mmu.c:xen_hvm_init_mmu_ops)?
> >> 
> >> No, it's not.
> >  
> > well, it should, not to fix this problem but because it is a significant
> > performance improvement when running on shadow
> 
> Well - if you have suggestions on how to do this (a) in 2.6.32.x, (b)
> without turning on CONFIG_XEN, and (c) without massive patching,
> them I'm all for it.

Can you issue hypercalls?
If so, it is just a matter of backporting:

commit 5915100106b8f14a38053ad6c03a664d208aeaa2
Author: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Date:   Thu Jun 17 14:22:52 2010 +0100

    x86: Call HVMOP_pagetable_dying on exit_mmap.
    
    When a pagetable is about to be destroyed, we notify Xen so that the
    hypervisor can clear the related shadow pagetable.
    
    Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
    Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>

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