Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261410AbUDHASs (ORCPT ); Wed, 7 Apr 2004 20:18:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261405AbUDHASs (ORCPT ); Wed, 7 Apr 2004 20:18:48 -0400 Received: from ppp-217-133-42-200.cust-adsl.tiscali.it ([217.133.42.200]:58315 "EHLO dualathlon.random") by vger.kernel.org with ESMTP id S261410AbUDHASr (ORCPT ); Wed, 7 Apr 2004 20:18:47 -0400 Date: Thu, 8 Apr 2004 02:18:45 +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: <20040408001845.GX26888@dualathlon.random> References: <4071D11B.1FEFD20A@amis.com> <20040405221641.GN2234@dualathlon.random> <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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <33900000.1081380891@flay> 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: 1211 Lines: 20 On Wed, Apr 07, 2004 at 04:34:51PM -0700, Martin J. Bligh wrote: > I measured it - IIRC it was 5-10% on kernel compile ... and that was on a > high ratio NUMA which it should have made *better* (as with highmem, the > PTEs can be allocated node locally). I'll try to dig up the old profiles. but this is a kind of machine where I assume you've plenty of ram and you really want pte_highmem enabled (the sysctl can still be added but you really must know what you're doing if you disable pte_highmem there), I was more interested to hear the impact on mid-low end 1-2G machines where pte_highmem isn't really necessary for most apps, and there the sysctl may be useful for general purpose too. If it payoffs significantly the sysctl could then be elaborated in an heuristic that prefers lowmem pagetables until a certain threshold, and then it fallbacks in highmem allocations, and the threshold depends on the highmem/lowmem ratio plus a further tuning via sysctl). - 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/