On Thu, 20 Jan 2011, Balbir Singh wrote:

> +     unmapped_page_control
> +                     [KNL] Available if CONFIG_UNMAPPED_PAGECACHE_CONTROL
> +                     is enabled. It controls the amount of unmapped memory
> +                     that is present in the system. This boot option plus
> +                     vm.min_unmapped_ratio (sysctl) provide granular control

min_unmapped_ratio is there to guarantee that zone reclaim does not
reclaim all unmapped pages.

What you want here is a max_unmapped_ratio.


>  {
> @@ -2297,6 +2320,12 @@ loop_again:
>                               shrink_active_list(SWAP_CLUSTER_MAX, zone,
>                                                       &sc, priority, 0);
>
> +                     /*
> +                      * We do unmapped page reclaim once here and once
> +                      * below, so that we don't lose out
> +                      */
> +                     reclaim_unmapped_pages(priority, zone, &sc);
> +
>                       if (!zone_watermark_ok_safe(zone, order,

Hmmmm. Okay that means background reclaim does it. If so then we also want
zone reclaim to be able to work in the background I think.
max_unmapped_ratio could also be useful to the zone reclaim logic.

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