Re: [PATCH 2/3] mm: page allocator: Calculate a better estimate ofNR_FREE_PAGES when memory is low and kswapd is awake

[Christoph Lameter]

On Mon, 23 Aug 2010, Mel Gorman wrote:

> This patch introduces zone_nr_free_pages() to take a slightly more accurate
> estimate of NR_FREE_PAGES while kswapd is awake. The estimate is not perfect
> and may result in cache line bounces but is expected to be lighter than the
> IPI calls necessary to continually drain the per-cpu counters while kswapd
> is awake.

The delta of the counters could also be reduced to increase accuracy.
See refresh_zone_stat_thresholds().

Also would it be possible to add the summation function to vmstat? It may
be useful elsewhere.

A new function like

	zone_page_state_snapshot()

or so?


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