linux-kernel - Re: [PATCH][RF C/T/D] Unmapped page cache control

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Date:	Mon, 15 Mar 2010 09:48:05 +0200
From:	Avi Kivity <avi@...hat.com>
To:	balbir@...ux.vnet.ibm.com
CC:	KVM development list <kvm@...r.kernel.org>,
	Rik van Riel <riel@...riel.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][RF C/T/D] Unmapped page cache control - via boot parameter

On 03/15/2010 09:22 AM, Balbir Singh wrote:
> Selectively control Unmapped Page Cache (nospam version)
>
> From: Balbir Singh<balbir@...ux.vnet.ibm.com>
>
> This patch implements unmapped page cache control via preferred
> page cache reclaim. The current patch hooks into kswapd and reclaims
> page cache if the user has requested for unmapped page control.
> This is useful in the following scenario
>
> - In a virtualized environment with cache!=none, we see
>    double caching - (one in the host and one in the guest). As
>    we try to scale guests, cache usage across the system grows.
>    The goal of this patch is to reclaim page cache when Linux is running
>    as a guest and get the host to hold the page cache and manage it.
>    There might be temporary duplication, but in the long run, memory
>    in the guests would be used for mapped pages.
>    

Well, for a guest, host page cache is a lot slower than guest page cache.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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