From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 9F5BC6B00A5 for ; Sun, 10 May 2009 09:55:36 -0400 (EDT) Received: by yw-out-1718.google.com with SMTP id 5so1218828ywm.26 for ; Sun, 10 May 2009 06:56:28 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20090510144533.167010a9@lxorguk.ukuu.org.uk> References: <20090430181340.6f07421d.akpm@linux-foundation.org> <20090507151039.GA2413@cmpxchg.org> <20090507134410.0618b308.akpm@linux-foundation.org> <20090508081608.GA25117@localhost> <20090508125859.210a2a25.akpm@linux-foundation.org> <20090508230045.5346bd32@lxorguk.ukuu.org.uk> <2f11576a0905100159m32c36a9ep9fb7cc5604c60b2@mail.gmail.com> <1241946446.6317.42.camel@laptop> <2f11576a0905100236u15d45f7fm32d470776659cfec@mail.gmail.com> <20090510144533.167010a9@lxorguk.ukuu.org.uk> Date: Sun, 10 May 2009 22:56:27 +0900 Message-ID: <2f11576a0905100656x51386193tb28e169651c3522d@mail.gmail.com> Subject: Re: [PATCH -mm] vmscan: make mapped executable pages the first class citizen From: KOSAKI Motohiro Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Alan Cox Cc: Peter Zijlstra , Andrew Morton , Wu Fengguang , hannes@cmpxchg.org, riel@redhat.com, linux-kernel@vger.kernel.org, tytso@mit.edu, linux-mm@kvack.org, elladan@eskimo.com, npiggin@suse.de, cl@linux-foundation.org, minchan.kim@gmail.com List-ID: Hi >> I don't oppose this policy. PROT_EXEC seems good viewpoint. > > I don't think it is that simple > > Not only can it be abused but some systems such as java have large > PROT_EXEC mapped environments, as do many other JIT based languages. hmm I don't think this patch change JIT behavior. JIT makes large executable _anon_ pages. but page_mapping(anon-page) return NULL. Thus, the logic do nothing. > Secondly it moves the pressure from the storage volume holding the system > binaries and libraries to the swap device which already has to deal with > a lot of random (and thus expensive) I/O, as well as the users filestore > for mapped objects there - which may even be on a USB thumbdrive. true. My SSD have high speed random reading charactastics. > I still think the focus is on the wrong thing. We shouldn't be trying to > micro-optimise page replacement guesswork - we should be macro-optimising > the resulting I/O performance. My disks each do 50MBytes/second and even with the > Gnome developers finest creations that ought to be enough if the rest of > the system was working properly. Yes, mesurement is essential. -- 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/ . Don't email: email@kvack.org