[PATCH 0/4] powernv: kvm: numa fault improvement

Alexander Graf agraf at suse.de
Tue Jan 21 01:48:36 EST 2014

On 15.01.2014, at 07:36, Liu ping fan <kernelfans at gmail.com> wrote:

> On Thu, Jan 9, 2014 at 8:08 PM, Alexander Graf <agraf at suse.de> wrote:
>> On 11.12.2013, at 09:47, Liu Ping Fan <kernelfans at gmail.com> 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 at vger.kernel.org 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?


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