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

    On 09/10/2010 10:16 AM, Peter Zijlstra wrote:
    > 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....

    Maybe but at this point it might be a bit too late. The allocator has
    been that way since the beginning.

    > 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.

    Nice catch. Fortunately, the -km allocator isn't currently being used
    in upstrea although it was enabled for linux-next a couple of days
    ago. I'll fix it up.

    Thank you.


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