Re: [PATCH] x86-32: Allocate irq stacks seperate from percpu area

[Tejun Heo]

Hello, Eric.

On 10/27/2010 10:55 PM, Eric Dumazet wrote:
> I changed the User/Kernel split from 3G/1G to 1G/3G so that I have
> LOWMEM on both nodes. Still pcpu allocates all percpu from node0.
...
> [    0.000000] setup_percpu: NR_CPUS:64 nr_cpumask_bits:64 nr_cpu_ids:16 nr_node_ids:8
> [    0.000000] PERCPU: Embedded 16 pages/cpu @bea00000 s41984 r0 d23552 u131072
> [    0.000000] pcpu-alloc: s41984 r0 d23552 u131072 alloc=1*2097152
> [    0.000000] pcpu-alloc: [0] 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 
> [    0.000000] setup_percpu: cpu=0 early_cpu_to_node()=0
> [    0.000000] setup_percpu: cpu=1 early_cpu_to_node()=0
> [    0.000000] setup_percpu: cpu=2 early_cpu_to_node()=0
> [    0.000000] setup_percpu: cpu=3 early_cpu_to_node()=0
> [    0.000000] setup_percpu: cpu=4 early_cpu_to_node()=0
> [    0.000000] setup_percpu: cpu=5 early_cpu_to_node()=0
> [    0.000000] setup_percpu: cpu=6 early_cpu_to_node()=0
> [    0.000000] setup_percpu: cpu=7 early_cpu_to_node()=0
> [    0.000000] setup_percpu: cpu=8 early_cpu_to_node()=0
> [    0.000000] setup_percpu: cpu=9 early_cpu_to_node()=0
> [    0.000000] setup_percpu: cpu=10 early_cpu_to_node()=0
> [    0.000000] setup_percpu: cpu=11 early_cpu_to_node()=0
> [    0.000000] setup_percpu: cpu=12 early_cpu_to_node()=0
> [    0.000000] setup_percpu: cpu=13 early_cpu_to_node()=0
> [    0.000000] setup_percpu: cpu=14 early_cpu_to_node()=0
> [    0.000000] setup_percpu: cpu=15 early_cpu_to_node()=0

So, this is the problem.  percpu uses early_cpu_to_node() to determine
which cpu belongs to which NUMA node and according to it all CPUs are
on node 0, so percpu is configured accordingly.  I have no idea why
early_cpu_to_node() is set up like that tho.  Ingo, Thomas, any ideas?

-- 
tejun
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