Re: [BENCHMARKS] Namesys VM patches improve kbuild

Nikita Danilov
2004-01-26T11:19:50Z

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.)

It seems correct to make deactivation decision on the basic of recent
accesses to the page rather than by checking whether page was ever
accessed.

>

Nikita.