Re: [PATCH -v2 2/2] x86, acpi: Parse all SRAT cpu entries even have cpu num limitation

David Rientjes
2010-12-22T06:43:57Z

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@suse.de>
> 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@suse.de>
> Cc: David Rientjes <rientjes@google.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
>

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?