Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262788AbUDHV7v (ORCPT ); Thu, 8 Apr 2004 17:59:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262810AbUDHV7v (ORCPT ); Thu, 8 Apr 2004 17:59:51 -0400 Received: from ppp-217-133-42-200.cust-adsl.tiscali.it ([217.133.42.200]:31428 "EHLO dualathlon.random") by vger.kernel.org with ESMTP id S262788AbUDHV7t (ORCPT ); Thu, 8 Apr 2004 17:59:49 -0400 Date: Thu, 8 Apr 2004 23:59:46 +0200 From: Andrea Arcangeli To: "Martin J. Bligh" Cc: Ingo Molnar , Eric Whiting , akpm@osdl.org, linux-kernel@vger.kernel.org Subject: Re: -mmX 4G patches feedback [numbers: how much performance impact] Message-ID: <20040408215946.GU31667@dualathlon.random> References: <20040406115539.GA31465@elte.hu> <20040406155925.GW2234@dualathlon.random> <20040406192549.GA14869@elte.hu> <12640000.1081378705@flay> <20040407230140.GT26888@dualathlon.random> <29510000.1081380104@flay> <20040407231806.GV26888@dualathlon.random> <33900000.1081380891@flay> <20040408001845.GX26888@dualathlon.random> <1479132704.1081405456@[10.10.2.4]> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1479132704.1081405456@[10.10.2.4]> User-Agent: Mutt/1.4.1i X-GPG-Key: 1024D/68B9CB43 13D9 8355 295F 4823 7C49 C012 DFA1 686E 68B9 CB43 X-PGP-Key: 1024R/CB4660B9 CC A0 71 81 F4 A0 63 AC C0 4B 81 1D 8C 15 C8 E5 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1307 Lines: 24 On Wed, Apr 07, 2004 at 11:24:16PM -0700, Martin J. Bligh wrote: > Instead of fiddling with tuning knobs, I'd prefer to just do the UKVA > idea I've proposed before, and let each process have their own pagetables > mapped permanently ;-) that will have you pay for pte-highmem even in non-highmem machines. I'm always been against your above idea ;) It can speedup mmap a bit for some uncommon case but I believe your slowdown comes from the page faults after exeve and startup not from mmap with the kernel compile, and worst of all for non-highmem too (no sysctl or tuning knob can save you then). Amittedly some mmap intensive workload can get a slight speedup compared to pte-highmem but I don't think it's common and it has the potential of slowing down the page faults especially in short lived tasks even w/o highmem. What I found attractive was the persistent kmap in userspace, but that idea breaks with threading, and Andrew found another way that is to make the page fault interruptible so it doesn't seem very worthwhile anymore even w/o threading. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/