From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756005Ab2AYQcg (ORCPT ); Wed, 25 Jan 2012 11:32:36 -0500 Received: from ssl.dlh.net ([91.198.192.8]:34719 "EHLO ssl.dlh.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752648Ab2AYQcf (ORCPT ); Wed, 25 Jan 2012 11:32:35 -0500 X-Greylist: delayed 627 seconds by postgrey-1.27 at vger.kernel.org; Wed, 25 Jan 2012 11:32:35 EST Message-ID: <4F202C2E.7040100@dlh.net> Date: Wed, 25 Jan 2012 17:22:06 +0100 From: Peter Lieven User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.23) Gecko/20110921 Thunderbird/3.1.15 MIME-Version: 1.0 To: linux-kernel@vger.kernel.org Subject: free page zeroing and ksm Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi all, working a lot with KVM and KSM I came across the question if Linux (like e.g. Windows) zeroes out free pages after usage. I came across some patches for page sanitization which where submitted in 2009 and have not been merged for various reasons. Working with memory deduplication the primary goal is not sanitization of the pages, but have them not contain any garbage after they are freed. My question is if there is any mechanism in Linux to zero out unused pages? I found some people claiming that there is such a mechanism, but I found no reference. If there is not would it be possible to implement a kernel process that scans for unused pages and zeroes them out during idle time? Thanks, Peter