* Andrew Morton <a...@linux-foundation.org> wrote:
> On Wed, 26 Jun 2013 11:22:48 +0200 Ingo Molnar <mi...@kernel.org> wrote:
>
> > except that on 32 TB
> > systems we don't spend ~2 hours initializing 8,589,934,592 page heads.
>
> That's about a million a second which is crazy slow - even my
> prehistoric desktop is 100x faster than that.
>
> Where's all this time actually being spent?
See the earlier part of the thread - apparently it's spent initializing
the page heads - remote NUMA node misses from a single boot CPU, going
across a zillion cross-connects? I guess there's some other low hanging
fruits as well - so making this easier to profile would be nice. The
profile posted was not really usable.
Btw., NUMA locality would be another advantage of on-demand
initialization: actual users of RAM tend to allocate node-local
(especially on large clusters), so any overhead will be naturally lower.
Thanks,
Ingo
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