On Thu, Dec 13, 2012 at 10:41:04AM +0000, Mel Gorman wrote:

On Wed, Dec 12, 2012 at 04:43:35PM -0500, Johannes Weiner wrote:

quoted

In certain cases (kswapd reclaim, memcg target reclaim), a fixed
minimum amount of pages is scanned from the LRU lists on each
iteration, to make progress.

Do not make this minimum bigger than the respective LRU list size,
however, and save some busy work trying to isolate and reclaim pages
that are not there.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

This looks like a corner case where the LRU size would have to be smaller
than SWAP_CLUSTER_MAX. Is that common enough to care? It looks correct,
I'm just curious.

We have one lruvec per memcg per zone, so consider memory cgroups in a
NUMA environment: NR_MEMCG * (NR_NODES - 1) * NR_LRU_LISTS permanently
empty lruvecs, assuming the memory of one cgroup is bound to one node.

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