Re: [BENCHMARKS] Namesys VM patches improve kbuild

[Nick Piggin <piggin@cyberone.com.au>]

Nikita Danilov wrote:

>Nick Piggin writes:
> > 
>
>[...]
>
> > 
> > But by clearing the referenced bit when below the reclaim_mapped
> > threshold, you're throwing this information away.
> > 
> > Say you have 16 mapped pages on the active list, 8 referenced, 8 not.
> > You do a !reclaim_mapped scan. Your 16 pages are now in the same
> > order and none are referenced. You now do a reclaim_mapped scan and
> > reclaim 8 pages. 4 of them were the referenced ones, 4 were not.
> > 
> > With my change, you would reclaim all 8 non referenced pages.
>
>Which is wrong, because none of them was referenced _recently_. These
>pages are cold, according to the VM's notion of hotness. (Long time
>probably has passed between !reclaim_mapped and reclaim_mapped scans in
>your example.)
>

Well you'd have to admit the referenced pages are hotter, but
I guess I can't argue with the numbers: it must not be very
significant.

I just wonder why your patch makes such an improvement. You're
basically putting mapped pages to one side until reclaim_mapped,
which is similar to what my patch does, right?


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