Re: [PATCH 1/3] slqb: Do not use DEFINE_PER_CPU for per-node data

[Pekka Enberg <penberg@cs.helsinki.fi>]

On Mon, Sep 21, 2009 at 4:04 PM, Mel Gorman <mel@csn.ul.ie> wrote:
>> The "per-cpu" area in this case is actually a per-node area. This implied that
>> it was either racing (but the locking looked sound), a buffer overflow (but
>> I couldn't find one) or the per-cpu areas were being written to by something
>> else unrelated.
>
> This latter guess was close to the mark but not for the reasons I was
> guessing. There isn't magic per-cpu-area-freeing going on. Once I examined
> the implementation of per-cpu data, it was clear that the per-cpu areas for
> the node IDs were never being allocated in the first place on PowerPC. It's
> probable that this never worked but that it took a long time before SLQB
> was run on a memoryless configuration.
>
> This patch would replace patch 1 of the first hatchet job I did. It's possible
> a similar patch is needed for S390. I haven't looked at the implementation
> there and I don't have a means of testing it.

Other architectures could be affected as well which makes me think
"hatchet job number one" is the way forward. Nick?

                        Pekka

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