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

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Message-ID: <alpine.DEB.2.00.1012212230580.9505@chino.kir.corp.google.com>
Date:	Tue, 21 Dec 2010 22:43:44 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Venkatesh Pallipadi <venki@...gle.com>
cc:	Yinghai Lu <yinghai@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Nikanth Karthikesan <knikanth@...e.de>,
	"Zheng, Shaohui" <shaohui.zheng@...el.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Bjorn Helgaas <bjorn.helgaas@...com>,
	Nikhil Rao <ncrao@...gle.com>,
	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
Subject: Re: [PATCH -v2 2/2] x86, acpi: Parse all SRAT cpu entries even have
 cpu num limitation

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@...e.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@...e.de>
>     Cc: David Rientjes <rientjes@...gle.com>
>     Signed-off-by: Andrew Morton <akpm@...ux-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?
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