Re: [PATCH -v2 2/2] x86, acpi: Parse all SRAT cpu entries even havecpu num limitation
From: Venkatesh Pallipadi
Date: Wed Dec 22 2010 - 15:28:37 EST
On Tue, Dec 21, 2010 at 10:43 PM, David Rientjes <rientjes@xxxxxxxxxx> wrote:
> On Mon, 20 Dec 2010, Venkatesh Pallipadi wrote:
>
>> git bisect seems to narrow this down to the change below.
>>
>> Thanks,
>> Venki
>>
>> $ git bisect visualize
>> commit 50f2d7f682f9c0ed58191d0982fe77888d59d162
>> Author: Nikanth Karthikesan <knikanth@xxxxxxx>
>> Date: Thu Sep 30 17:34:10 2010 +0530
>>
>> x86, numa: Assign CPUs to nodes in round-robin manner on fake NUMA
>>
>> commit d9c2d5ac6af87b4491bff107113aaf16f6c2b2d9 "x86, numa: Use near(er)
>> online node instead of roundrobin for NUMA" changed NUMA initialization on
>> Intel to choose the nearest online node or first node. Fake NUMA would be
>> better of with round-robin initialization, instead of the all CPUS on
>> first node. Change the choice of first node, back to round-robin.
>>
>> For testing NUMA kernel behaviour without cpusets and NUMA aware
>> applications, it would be better to have cpus in different nodes, rather
>> than all in a single node. With cpusets migration of tasks scenarios
>> cannot not be tested.
>>
>> I guess having it round-robin shouldn't affect the use cases for all cpus
>> on the first node.
>>
>> The code comments in arch/x86/mm/numa_64.c:759 indicate that this used to
>> be the case, which was changed by commit d9c2d5ac6. It changed from
>> roundrobin to nearer or first node. And I couldn't find any reason for
>> this change in its changelog.
>>
>> Signed-off-by: Nikanth Karthikesan <knikanth@xxxxxxx>
>> Cc: David Rientjes <rientjes@xxxxxxxxxx>
>> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>>
>
> Peter just merged my NUMA emulation fixes into the x86 tree, could you try
> applying Yinghai's series on top of x86/linux-2.6-tip.git#x86/numa and see
> if the problem persists?
>
> On a different topic: Yinghai, do you think you could base your series off
> of Tejun's x86_32/x86_64 NUMA unification series since it already
> duplicates some of the work?
>
Yes. #x86/numa kernel works fine both with and without Yinghai's series.
I am assuming those changes are lined up for .38. Is there any
specific fix that can make into .37 to fix this regression?
Thanks,
Venki
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