Re: [REPOST] [PATCH 3/3] Provide control over unmapped pages (v3)

Christoph Lameter
2011-01-20T15:00:13Z

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.