Re: [Xen-devel] vnif socket buffer mistaken for pagetable page causes major performance problem

[Herbert van den Bergh <Herbert.van.den.Bergh@xxxxxxxxxx>]

Gianluca Guida wrote:
> Herbert van den Bergh wrote:
> > > Can you be a little more specific about what is the performance loss,
> > Network throughput was reduced to 10% of normal.
> > > in what workload,
> > A network send throughput test using netperf.
> This is with a Linux guest (HVM of course), right?
Right.

> > > and what heuristic you found to be wrong in this case?
> > The access pattern to the memory page that was recognized as a 
> > pagetable access was a regular memcpy doing 4 byte aligned writes 
> > into a newly allocated page.  I'm not that familiar with the shadow 
> > pagetable code, so I don't know how "wrong" this is, just that it 
> > caused a false positive on this type of memory access.
> Most probably the guest OS is recycling a page that used to be a 
> pagetable and that is still shadowed.
> Thanks,
> Gianluca
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel