Messages in this thread | | | Subject | Re: [patch 00/23] Slab defragmentation V6 | From | Lee Schermerhorn <> | Date | Thu, 08 Nov 2007 15:58:15 -0500 |
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On Thu, 2007-11-08 at 11:12 -0800, Christoph Lameter wrote: > On Thu, 8 Nov 2007, Mel Gorman wrote: > > > On Tue, 2007-11-06 at 17:11 -0800, Christoph Lameter wrote: > > > Slab defragmentation is mainly an issue if Linux is used as a fileserver > > > > Was hoping this would get renamed to SLUB Targetted Reclaim from > > discussions at VM Summit. As no copying is taking place, it's confusing > > to call it defragmentation to me anyway. Not a major deal but it made > > reading the patches a little confusing. > > The problem is that people are focusing on one feature here and forget > about the rest. Targetted reclaim is one feature that was added later when > lumpy reclaim was added to the kernel. The primary intend of this patchset > was always to reduce the fragmentation. The name is appropriate and the > patchset will support copying of objects as soon as support for that is > added to the kick(). In that case the copying you are looking for will be > there. The simple implementation for the kick() methods is to simply copy > pieces of the reclaim code. That is what is included here. > > > > With lumpy reclaim slab defragmentation can be used to enhance the > > > ability to recover larger contiguous areas of memory. Lumpy reclaim currently > > > cannot do anything if a slab page is encountered. With slab defragmentation > > > that slab page can be removed and a large contiguous page freed. It may > > > be possible to have slab pages also part of ZONE_MOVABLE (Mel's defrag > > > scheme in 2.6.23) > > > > More terminology nit-pick - ZONE_MOVABLE is not defragmenting anything. > > It's just partitioning memory. The slab pages need to be 100% > > reclaimable or movable for that to happen but even with targetted > > reclaim, some dentries such as the root directory one cannot be > > reclaimed, right? > > 100%? I am so fond of these categorical statements .... > > ZONE_MOVABLE also contains mlocked pages that are also not reclaimable. > The question is at what level would it be possible to make them MOVABLE? > It may take some improvements to the kick() methods to make eviction more > reliable. Allowing the moving of objects in the kick() methods will > likely get usthere.
Christoph: Although mlocked pages are not reclaimable, they ARE migratable. You fixed that a long time ago. [And I just verified with memtoy.] Doesn't this make them "movable"?
Lee
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