From mboxrd@z Thu Jan 1 00:00:00 1970 From: KOSAKI Motohiro Subject: Re: [PATCH 0/3] Unmapped page cache control (v5) Date: Fri, 1 Apr 2011 12:18:38 +0900 (JST) Message-ID: <20110401121825.A875.A69D9226@jp.fujitsu.com> References: <20110330052819.8212.1359.stgit@localhost6.localdomain6> <20110331214033.GA2904@dastard> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Cc: kosaki.motohiro@jp.fujitsu.com, Balbir Singh , linux-mm@kvack.org, akpm@linux-foundation.org, npiggin@kernel.dk, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, cl@linux.com, kamezawa.hiroyu@jp.fujitsu.com To: Dave Chinner Return-path: In-Reply-To: <20110331214033.GA2904@dastard> Sender: owner-linux-mm@kvack.org List-Id: kvm.vger.kernel.org > On Wed, Mar 30, 2011 at 11:00:26AM +0530, Balbir Singh wrote: > > > > The following series implements page cache control, > > this is a split out version of patch 1 of version 3 of the > > page cache optimization patches posted earlier at > > Previous posting http://lwn.net/Articles/425851/ and analysis > > at http://lwn.net/Articles/419713/ > > > > Detailed Description > > ==================== > > 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=writethrough, 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. > > What does this do that "cache=none" for the VMs and using the page > cache inside the guest doesn't acheive? That avoids double caching > and doesn't require any new complexity inside the host OS to > acheive... Right. "cache=none" has no double caching issue and KSM already solved cross gues cache sharing. So, I _guess_ this is not a core motivation of his patch. But I'm not him. I'm not sure. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org