Re: [RFC PATCH 1/2] perf_events: add support for per-cpuper-cgroup monitoring (v3)

[Peter Zijlstra]

On Thu, 2010-09-09 at 23:41 +0200, Stephane Eranian wrote:
> > alloc_percpu() is zalloc_percpu() in fact, memory is already cleared.
> >
> I remember thinking about this and trying to trace to the code down
> to figure this out. But it is rather complicated. If alloc_percpu() always
> clears the memory, then I think that calling is zalloc_percpu()
> would be more helpful.... 

pcpu_populate_chunk() in mm/percpu-vm.c does indeed do that memset, the
one in mm/percpu-km.c does not.

It is not obviously clear to me the -km allocator does indeed result in
zero filled memory.

Tejun?
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