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

On 15.01.2014, at 07:36, Liu ping fan [off-list ref] wrote:

On Thu, Jan 9, 2014 at 8:08 PM, Alexander Graf [off-list ref] wrote:

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On 11.12.2013, at 09:47, Liu Ping Fan [off-list ref] wrote:
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This series is based on Aneesh's series  "[PATCH -V2 0/5] powerpc: =

mm: Numa faults support for ppc64"

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For this series, I apply the same idea from the previous thread =

"[PATCH 0/3] optimize for powerpc _PAGE_NUMA"

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(for which, I still try to get a machine to show nums)
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But for this series, I think that I have a good justification -- the =

fact of heavy cost when switching context between guest and host,

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which is  well known.

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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.

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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)
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If my suppose is correct, will CCing kvm@vger.kernel.org from next =

version.

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This translates to me as "This is an RFC"?
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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?


Alex