Messages in this thread | | | Date | Mon, 22 Jan 2007 21:17:34 -0500 | From | Rik van Riel <> | Subject | Re: Why active list and inactive list? |
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Christoph Lameter wrote: > On Mon, 22 Jan 2007, Rik van Riel wrote: > >> It would be really nice if we came up with a page replacement >> algorithm that did not need many extra heuristics to make it >> work... > > I guess the "clock" type algorithms are the most promising in that > area. What happened to all those advanced page replacement endeavors? > What is the most promising of those? You seem to have done a lot of work > on those.
CLOCK-Pro seems the most promising algorithm, because it can act well both as a first level cache (operating system running applications) and as a second level cache (operating system running as a file server), because it tracks both recency and frequency well.
However, there are a few unanswered questions on clock-pro.
The big one is how we are to do some background aging in a clock-pro system, so referenced bits don't just pile up when the VM has enough memory - otherwise we might not know the right pages to evict when a new process starts up and starts allocating lots of memory.
At least we've solved the problems of keeping track of the recently evicted pages in a cheap way, and balancing the pressure/hotness of different caches against each other.
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