From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753219AbZEIKU1 (ORCPT ); Sat, 9 May 2009 06:20:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751228AbZEIKUO (ORCPT ); Sat, 9 May 2009 06:20:14 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:36439 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750936AbZEIKUM (ORCPT ); Sat, 9 May 2009 06:20:12 -0400 From: KOSAKI Motohiro To: Christoph Lameter Subject: Re: [PATCH -mm] vmscan: make mapped executable pages the first class citizen Cc: kosaki.motohiro@jp.fujitsu.com, Elladan , Rik van Riel , Lee Schermerhorn , Peter Zijlstra , Wu Fengguang , Andrew Morton , "linux-kernel@vger.kernel.org" , "tytso@mit.edu" , "linux-mm@kvack.org" , Nick Piggin , Johannes Weiner In-Reply-To: References: <20090508034054.GB1202@eskimo.com> Message-Id: <20090509191818.3AD8.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.50.07 [ja] Date: Sat, 9 May 2009 19:20:09 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Thu, 7 May 2009, Elladan wrote: > > > > Nobody (except you) is proposing that we completely disable > > > the eviction of executable pages. I believe that your idea > > > could easily lead to a denial of service attack, with a user > > > creating a very large executable file and mmaping it. > > The amount of mlockable pages is limited via ulimit. We can already make > the pages unreclaimable through mlock(). > > > I don't know of any distro that applies default ulimits, so desktops are > > already susceptible to the far more trivial "call malloc a lot" or "fork bomb" > > attacks. Plus, ulimits don't help, since they only apply per process - you'd > > need a default mem cgroup before this mattered, I think. > > The point remains that the proposed patch does not solve the general > problem that we encounter with exec pages of critical components of the > user interface being evicted from memory. > > Do we have test data that shows a benefit? The description is minimal. Rik > claimed on IRC that tests have been done. If so then the patch description > should include the tests. Which loads benefit from this patch? > > A significant change to the reclaim algorithm also needs to > have a clear description of the effects on reclaim behavior which is also > lacking. btw, This is very good news to me. Recently I've taked sevaral time for reproducing this issue. but I have no luck. I'm interesting its test-case. Thanks.