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Date: Wed, 15 Jul 2015 15:43:51 -0700
From: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
To: Tejun Heo <tj@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>,
 David Rientjes <rientjes@google.com>,
 Benjamin Herrenschmidt <benh@kernel.crashing.org>,
 Paul Mackerras <paulus@samba.org>, Anton Blanchard <anton@samba.org>,
 Peter Zijlstra <peterz@infradead.org>, linuxppc-dev@lists.ozlabs.org,
 linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 1/2] powerpc/numa: fix cpu_to_node() usage during boot
Message-ID: <20150715224351.GH38815@linux.vnet.ibm.com>
References: <20150702230202.GA2807@linux.vnet.ibm.com>
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On 15.07.2015 [16:35:16 -0400], Tejun Heo wrote:
> Hello,
> 
> On Thu, Jul 02, 2015 at 04:02:02PM -0700, Nishanth Aravamudan wrote:
> > we currently emit at boot:
> > 
> > [    0.000000] pcpu-alloc: [0] 0 1 2 3 [0] 4 5 6 7 
> > 
> > After this commit, we correctly emit:
> > 
> > [    0.000000] pcpu-alloc: [0] 0 1 2 3 [1] 4 5 6 7 
> 
> JFYI, the numbers in the brackets aren't NUMA node numbers but percpu
> allocation group numbers and they're not split according to nodes but
> percpu allocation units.  In both cases, there are two units each
> serving 0-3 and 4-7.  In the above case, because it wasn't being fed
> the correct NUMA information, both got assigned to the same group.  In
> the latter, they got assigned to different ones but even then if the
> group numbers match NUMA node numbers, that's just a coincidence.

Ok, thank you for clarifying! From a correctness perspective, even if
the numbers don't match NUMA nodes, should we expect the grouping to be
split along NUMA topology?

-Nish