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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 10.11.11 at 16:55, Gianluca Guida <glguida@xxxxxxxxx> wrote:
> On Thu, Nov 10, 2011 at 7:11 AM, Jan Beulich <JBeulich@xxxxxxxx> 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.
> 
> Can you please try the inline patch? Unfortunately I have no unstable
> test machine or infrastructure at the moment, so I can;t really test
> it.

The testing on the customer system (4.0.2 based) went fine, so
please formally submit the patch (indicating the need to backport
to 4.0-testing and 4.1-testing).

Thanks, Jan

> I finally recalled a bit of details about this patch, so this check is
> clearly a bug as-it-is: it was written with the assumption that all
> the HVM guests would have been Windows guests with particular
> PV-drivers, so I wasn't particularly nice with the checks.
> 
> Thank you,
> Gianluca
> 
> diff -r 068d3d55ce6e xen/arch/x86/mm/shadow/multi.c
> --- a/xen/arch/x86/mm/shadow/multi.c    Tue Nov 01 19:03:38 2011 +0000
> +++ b/xen/arch/x86/mm/shadow/multi.c    Thu Nov 10 16:46:50 2011 -0800
> @@ -2723,8 +2723,9 @@
>             || ( !v->domain->arch.paging.shadow.pagetable_dying_op
>                  &&
> v->arch.paging.shadow.last_emulated_mfn_for_unshadow == mfn_x(gmfn) )
> )
>           && sh_mfn_is_a_page_table(gmfn)
> -         && !(mfn_to_page(gmfn)->shadow_flags
> -              & (SHF_L2_32|SHF_L2_PAE|SHF_L2H_PAE|SHF_L4_64)) )
> +         && (!v->domain->arch.paging.shadow.pagetable_dying_op ||
> +             !(mfn_to_page(gmfn)->shadow_flags
> +               & (SHF_L2_32|SHF_L2_PAE|SHF_L2H_PAE|SHF_L4_64))) )
>      {
>          perfc_incr(shadow_early_unshadow);
>          sh_remove_shadows(v, gmfn, 1, 0 /* Fast, can fail to unshadow */ );





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