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On Wed, 23 Jan 2002, Duraid Madina wrote: > I'm sure at least some of you will immediately recognize these words: > > >Swap allocation is terrible. Linux uses a linear array which it scans > >looking for a free swap block. It does a relatively simple swap > >cluster cache, but eats the full linear scan if that fails which can be > >terribly nasty. The swap clustering algorithm is a piece of crap, > >too -- once swap becomes fragmented, the linux swapper falls on its > >face. Agreed, scanning for a swap block can take too much CPU on large machines. We've seen this happen ... > >It does read-ahead based on the swapblk which wouldn't be bad if it > >clustered writes by object or didn't have a fragmentation problem. > >As it stands, their read clustering is useless. Swap deallocation is > >fast since they are using a simple reference count array. Swap readahead improvements very much welcome. > >File read-ahead is half-hazard at best. How so? File read-ahead seems to work pretty well. > >The paging queues ( determing the age of the page and whether to > >free or clean it) need to be written... the algorithms being used > >are terrible. Fixed in -rmap, http://surriel.com/patches/ > >Linux does not appear to do any page coloring whatsoever, but it would > >not be hard to add it in. Not sure how page colouring would interact with the buddy allocator, though ;) > Where does Linux stand, three years on? An O(1) scheduler is > nice, but I tell you what'd be even nicer... I'm working on some of the above issues for the -rmap VM; if there's something else which really bugs you, I accept patches ;) cheers, Rik -- "Linux holds advantages over the single-vendor commercial OS" -- Microsoft's "Competing with Linux" document http://www.surriel.com/ http://distro.conectiva.com/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | |||||||||
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