Re: [PATCH 1/2] Zone reclaim V2

[Andi Kleen]

On Tue, Dec 06, 2005 at 09:24:44AM -0800, Christoph Lameter wrote:
> Zone reclaim allows the reclaiming of pages from a zone if the number of free
> pages falls below the watermark even if other zones still have enough pages
> available. Zone reclaim is of particular importance for NUMA machines. It can
> be more beneficial to reclaim a page than taking the performance penalties
> that come with allocating a page on a remote zone.
> 
> The patch replaces Martin Hick's zone reclaim function (which was never
> working properly).
> 
> An arch can control zone_reclaim by setting zone_reclaim_mode during bootup
> if it is discovered that the kernel is running on an NUMA configuration.

Looks much better. Thanks. But how about auto controlling the variable in generic
code based on node_distance() (at least for the non node hotplug case)


> +/*
> + * Zone reclaim mode
> + *
> + * If non-zero call zone_reclaim when the number of free pages falls below
> + * the watermarks.
> + */
> +int zone_reclaim_mode;

I would mark it __read_mostly to avoid potential false sharing.

-Andi
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