Messages in this thread | | | Date | Mon, 13 Mar 2006 11:28:45 +0900 | From | "Magnus Damm" <> | Subject | Re: [PATCH 00/03] Unmapped: Separate unmapped and mapped pages |
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On 3/12/06, Peter Zijlstra <peter@programming.kicks-ass.net> wrote: > On Fri, 2006-03-10 at 14:19 +0100, Magnus Damm wrote: > > 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. > > This sounds wrong, the active and inactive lists are balanced to a 1:1 > ratio. This is happens because the scan speed is directly proportional > to the size of the list. Hence the largest list will shrink fastest - > this gives a natural balance to equal sizes.
Yes, you are explaining the current 2.6 behaviour much better. Also, some balancing logic with nr_scan_active/nr_scan_inactive is present in the code today. I'm not entirely sure about the purpose of that code.
Thanks,
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