On (19/04/07 21:11), Andi Kleen didst pronounce: > > We likely need actual defragmentation support. > > To be honest it looks quite pointless before this is solved. So far it is > not even clear if it is feasible to solve it. >
I've written a proposal in an OLS paper on how such a mechanism would work based on the existing page migration feature. However, it depends heavily on grouping pages by mobility to work because without it, a defragmentation mechanism will be ineffective. I was holding off posting a RFC until I saw how fragmentation avoidance got on in the next merge window and find the time to prototype it. Without going into unnecessary detail, the end result of a compaction run is that all movable pages are at the end of the zone and all unmovable pages are at the start with contiguous free space in the middle. Grouping pages by mobility as it is biases the location of non-movable pages towards the lower PFNs. Assuming it had a reasonable level of success, even high-order ramfs pages that were unmovable should work out. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
