Messages in this thread | | | Date | Fri, 10 Mar 2006 14:19:55 +0100 | From | "Magnus Damm" <> | Subject | Re: [PATCH 00/03] Unmapped: Separate unmapped and mapped pages |
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On 3/10/06, Arjan van de Ven <arjan@infradead.org> wrote: > > Apply on top of 2.6.16-rc5. > > > > Comments? > > > my big worry with a split LRU is: how do you keep fairness and balance > between those LRUs? This is one of the things that made the 2.4 VM suck > really badly, so I really wouldn't want this bad...
Yeah, I agree this is important. I think linux-2.4 tried to keep the LRU list lengths in a certain way (maybe 2/3 of all pages active, 1/3 inactive). In 2.6 there is no such thing, instead the number of pages scanned is related to the current scanning priority.
My current code just extends this idea which basically means that there is currently no relation between how many pages that sit in each LRU. The LRU with the largest amount of pages will be shrunk/rotated first. And on top of that is the guarantee logic and the reclaim_mapped threshold, ie the unmapped LRU will be shrunk first by default.
The current balancing code plays around with nr_scan_active and nr_scan_inactive, but I'm not entirely sure why that logic is there. If anyone can explain the reason behind that code I'd be happy to hear it.
Thanks,
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