From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261830AbUB1HBA (ORCPT ); Sat, 28 Feb 2004 02:01:00 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261832AbUB1HBA (ORCPT ); Sat, 28 Feb 2004 02:01:00 -0500 Received: from obsidian.spiritone.com ([216.99.193.137]:17883 "EHLO obsidian.spiritone.com") by vger.kernel.org with ESMTP id S261830AbUB1HA6 (ORCPT ); Sat, 28 Feb 2004 02:00:58 -0500 Date: Fri, 27 Feb 2004 23:00:44 -0800 From: "Martin J. Bligh" To: Andrea Arcangeli cc: Andrew Morton , Rik van Riel , linux-kernel@vger.kernel.org Subject: Re: 2.4.23aa2 (bugfixes and important VM improvements for the high end) Message-ID: <474350000.1077951643@[10.10.2.4]> In-Reply-To: <20040228064352.GP8834@dualathlon.random> References: <20040227173250.GC8834@dualathlon.random> <20040227122936.4c1be1fd.akpm@osdl.org> <20040227211548.GI8834@dualathlon.random> <162060000.1077919387@flay> <20040228023236.GL8834@dualathlon.random> <469160000.1077948622@[10.10.2.4]> <20040228064352.GP8834@dualathlon.random> X-Mailer: Mulberry/2.2.1 (Linux/x86) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > The last issue that we may run into are apps assuming the stack is at 3G > fixed, some jvm assumed that, but they should be fixed by now (at the > very least it's not hard at all to fix those). All the potential solutions we're discussing hit that problem so I don't see it matters much which one we choose ;-) > It also depends on the performance difference if this is worthwhile, if > the difference isn't very significant 4:4 will be certainly prefereable > so you can also allocate 4G in the same task for apps not using syscalls > or page faults or flood of network irqs. There are some things that may well help here: one is vsyscall gettimeofday, which will fix up the worst of the issues (the 30% figure you mentioned to me in Ottowa), the other is NAPI, which would help with the network stuff. Bill had a patch to allocate mmaps, etc down from the top of memory and thus elimininate TASK_UNMAPPED_BASE, and shift the stack back into the empty hole from 0-128MB of memory where it belongs (according to the spec). Getting rid of those two problems gives us back a little more userspace as well. Unfortunately it does seem to break some userspace apps making stupid assumptions, but if we have a neat way to mark the binaries (Andi was talking about personalities or something), we could at least get the big mem hogs to do that (databases, java, etc). I have a copy of Bill's patch in my tree if you want to take a look: ftp://ftp.kernel.org/pub/linux/kernel/people/mbligh/patches/2.6.3/2.6.3-mjb1/410-topdown That might make your 2.5/1.5 proposal more feasible with less loss of userspace. M