Linear reclaim V1

Linear Reclaim (V1)

When we are out of memory of a suitable size we enter reclaim. The current reclaim algorithm targets pages in LRU order, which is great for fairness but highly unsuitable if you desire pages at higher orders. To get pages of higher order we must shoot down a very high proportion of memory; >95% in a lot of cases.

This patch set adds a linear reclaim algorithm to the allocator. It targets groups of pages at the specified order rather than in lru order. Passing over each area at this size and assessing the likelyhood of reclaiming all of the pages within. If chances are high, we apply reclaim to all of the busy pages in this area in the hopes of consolidating a complete page at that order. This is designed to be used when we are out of higher order pages.

This patch set is particularly effective when utilised with an anti-fragmentation scheme which groups pages of similar reclaimability together.

As it stands we introduce a complete second reclaim algorithm. Once this has stablised it would make sense to merge the two algorithms. Targetting variable size blocks using pages at the end of the LRU as seeds. When operating at order 0 the algorithms would then be equivalent.

-apw

Base: 2.6.18-rc5-mm1

Patches:
o linear-reclaim-add-order-to-reclaim-path
o linear-reclaim-export-page_order-and-family
o linear-reclaim-pull-out-unfreeable-page-return
o linear-reclaim-add-pfn_valid_within-for-zone-holes
o linear-reclaim-core

Current version: V1

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