On Fri, Jul 20, 2012 at 10:34:28AM +0800, Xiao Guangrong wrote: > On 07/20/2012 08:39 AM, Marcelo Tosatti wrote: > > On Tue, Jul 17, 2012 at 09:53:29PM +0800, Xiao Guangrong wrote: > >> If it have no indirect shadow pages we need not protect any gfn, > >> this is always true for direct mmu without nested > >> > >> Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx> > > > > Xiao, > > > > What is the motivation? Numbers please. > > > > mmu_need_write_protect is the common path for both soft-mmu and > hard-mmu, checking indirect_shadow_pages can skip hash-table walking > for the case which is tdp is enabled without nested guest. I mean motivation as observation that it is a bottleneck. > I will post the Number after I do the performance test. > > > In fact, what case was the original indirect_shadow_pages conditional in > > kvm_mmu_pte_write optimizing again? > > > > They are the different paths, mmu_need_write_protect is the real > page fault path, and kvm_mmu_pte_write is caused by mmio emulation. Sure. What i am asking is, what use case is the indirect_shadow_pages optimizing? What scenario, what workload? See the "When to optimize" section of http://en.wikipedia.org/wiki/Program_optimization. Can't remember why indirect_shadow_pages was introduced in kvm_mmu_pte_write. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
