Re: x86-64: memset()/memcpy() not fully standards compliant

[Jan Beulich]

>>> On 06.01.12 at 11:37, Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:
>> > You would slow a critical fast path operation down for something
>> > that never happens?!?
>> 
>> It does happen, just (so far) not in-tree. It's a latent problem that's
>> just waiting for someone else to run into. Apart from large bootmem
>> allocations (where not even the latency of the memory clearing
> 
> Modern kernels are bootmem less.

It's not the traditional bootmem implementation anymore, but
alloc_bootmem() et al still exist, and still clear the allocated memory
(in __alloc_memory_core_early()). So there is a code path that can
validly be used (and it is this code path that is presenting one of the
problems with the non-pv-ops Xen kernels, as they're using flatmem
rather than sparsemem since their physical address space is always
fully continuous).

Jan

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