On (05/12/06 12:01), Christoph Lameter didst pronounce: > On Tue, 5 Dec 2006, Andrew Morton wrote: > > > > We always run reclaim against the whole zone not against parts. Why > > > would we start running reclaim against a portion of a zone? > > > > Oh for gawd's sake. > > Yes indeed. Another failure to answer a simple question. >
There are times you want to reclaim just part of a zone - specifically satisfying a high-order allocations. See sitations 1 and 2 from elsewhere in this thread. On a similar vein, there will be times when you want to migrate a PFN range for similar reasons. > > If you want to allocate a page from within the first 1/4 of a zone, and if > > all those pages are in use for something else then you'll need to run > > reclaim against the first 1/4 of that zone. Or fail the allocation. Or > > run reclaim against the entire zone. The second two options are > > self-evidently dumb. > > Why would one want to allocate from the 1/4th of a zone? (Are we still > discussing Mel's antifrag scheme or what is this about?) > Because you wanted contiguous blocks of pages. This is related to anti-frag because with anti-frag, reclaiming memory or migration memory will free up contiguous blocks. Without it, you're probably wasting your time. -- 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/
