* H. Peter Anvin <h...@zytor.com> wrote:
> On 06/23/2013 02:32 AM, Ingo Molnar wrote:
> >
> > * Ingo Molnar <mi...@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.
>
> Even better if we could start at the 1 GB level, which most of these
> really huge machines will have hardware support for.
That might be a bit too granular: if we hit such an uninitialized block of
memory we'd have to process 262,144 pages - potentially from an IRQ
handler that does GFP_ATOMIC... or other latency critical code.
With 2MB we'd have to on-demand initialize 512 pages, which shouldn't show
up during normal use.
Thanks,
Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
