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

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Date:	Thu, 20 Jan 2011 09:00:09 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Balbir Singh <balbir@...ux.vnet.ibm.com>
cc:	linux-mm@...ck.org, akpm@...ux-foundation.org, npiggin@...nel.dk,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	kosaki.motohiro@...fujitsu.com, kamezawa.hiroyu@...fujitsu.com
Subject: Re: [REPOST] [PATCH 3/3] Provide control over unmapped pages (v3)

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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