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SubjectRe: [RFC 2/2] x86_64, mm: Reinsert the absent memory

* Ingo Molnar <mingo@kernel.org> wrote:

> Yet another thing to consider would be to implement an initialization
> speedup of 3 orders of magnitude: initialize on the large page (2MB)
> grandularity and on-demand delay the initialization of the 4K granular
> struct pages [but still allocating them] - which I suspect are a good
> chunk of the overhead? That way we could initialize in 2MB steps and speed
> up the 2 hours bootup of 32 TB of RAM to 14 seconds...
>
> [ The cost would be one more branch in the buddy allocator, to detect
> not-yet-initialized 2 MB chunks as we encounter them. Acceptable I
> think. ]

One advantage of this scheme would be that we could use it on pretty much
any box, it would provide instant boot time speedups everywhere [a couple
of hundred msecs on a small 4GB box - significant I think] - and would
spread out and parallelize initialization to later stages.

Thanks,

Ingo


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