On 07/20/2012 07:09 PM, Marcelo Tosatti wrote: > 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? > Sorry, Marcelo, i do know why i completely misunderstood your mail. :( I am not sure whether this is a bottleneck, i just got it from code review, i will measure it to see if we can get benefit from it. :p > 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. > Please refer to: https://lkml.org/lkml/2011/5/18/174 -- 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
