On Wed, Jan 22, 2014 at 1:18 PM, Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> wrote: > Paul Mackerras <paulus@xxxxxxxxx> writes: > >> On Mon, Jan 20, 2014 at 03:48:36PM +0100, Alexander Graf wrote: >>> >>> On 15.01.2014, at 07:36, Liu ping fan <kernelfans@xxxxxxxxx> wrote: >>> >>> > On Thu, Jan 9, 2014 at 8:08 PM, Alexander Graf <agraf@xxxxxxx> wrote: >>> >> >>> >> On 11.12.2013, at 09:47, Liu Ping Fan <kernelfans@xxxxxxxxx> wrote: >>> >> >>> >>> This series is based on Aneesh's series "[PATCH -V2 0/5] powerpc: mm: Numa faults support for ppc64" >>> >>> >>> >>> For this series, I apply the same idea from the previous thread "[PATCH 0/3] optimize for powerpc _PAGE_NUMA" >>> >>> (for which, I still try to get a machine to show nums) >>> >>> >>> >>> But for this series, I think that I have a good justification -- the fact of heavy cost when switching context between guest and host, >>> >>> which is well known. >>> >> >>> >> This cover letter isn't really telling me anything. Please put a proper description of what you're trying to achieve, why you're trying to achieve what you're trying and convince your readers that it's a good idea to do it the way you do it. >>> >> >>> > Sorry for the unclear message. After introducing the _PAGE_NUMA, >>> > kvmppc_do_h_enter() can not fill up the hpte for guest. Instead, it >>> > should rely on host's kvmppc_book3s_hv_page_fault() to call >>> > do_numa_page() to do the numa fault check. This incurs the overhead >>> > when exiting from rmode to vmode. My idea is that in >>> > kvmppc_do_h_enter(), we do a quick check, if the page is right placed, >>> > there is no need to exit to vmode (i.e saving htab, slab switching) >>> > >>> >>> If my suppose is correct, will CCing kvm@xxxxxxxxxxxxxxx from next version. >>> >> >>> >> This translates to me as "This is an RFC"? >>> >> >>> > Yes, I am not quite sure about it. I have no bare-metal to verify it. >>> > So I hope at least, from the theory, it is correct. >>> >>> Paul, could you please give this some thought and maybe benchmark it? >> >> OK, once I get Aneesh to tell me how I get to have ptes with >> _PAGE_NUMA set in the first place. :) >> > > I guess we want patch 2, Which Liu has sent separately and I have > reviewed. http://article.gmane.org/gmane.comp.emulators.kvm.powerpc.devel/8619 > I am not sure about the rest of the patches in the series. > We definitely don't want to numa migrate on henter. We may want to do > that on fault. But even there, IMHO, we should let the host take the > fault and do the numa migration instead of doing this in guest context. > My patch does NOT do the numa migration in guest context( h_enter). Instead it just do a pre-check to see whether the numa migration is needed. If needed, the host will take the fault and do the numa migration as it currently does. Otherwise, h_enter can directly setup hpte without HPTE_V_ABSENT. And since pte_mknuma() is called system-wide periodly, so it has more possibility that guest will suffer from HPTE_V_ABSENT.(as my previous reply, I think we should also place the quick check in kvmppc_hpte_hv_fault ) Thx, Fan > -aneesh > -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
