Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755055AbZJTHiK (ORCPT ); Tue, 20 Oct 2009 03:38:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751552AbZJTHiI (ORCPT ); Tue, 20 Oct 2009 03:38:08 -0400 Received: from hera.kernel.org ([140.211.167.34]:42376 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751137AbZJTHiH (ORCPT ); Tue, 20 Oct 2009 03:38:07 -0400 Message-ID: <4ADD6915.7000909@kernel.org> Date: Tue, 20 Oct 2009 16:39:01 +0900 From: Tejun Heo User-Agent: Thunderbird 2.0.0.23 (X11/20090817) MIME-Version: 1.0 To: Eric Dumazet CC: Ingo Molnar , Jiri Kosina , Jeff Mahoney , Peter Zijlstra , Linux Kernel Mailing List , Tony Luck , Fenghua Yu , linux-ia64@vger.kernel.org Subject: Re: Commit 34d76c41 causes linker errors on ia64 with NR_CPUS=4096 References: <4ADB967A.4080707@suse.com> <20091020061557.GE8550@elte.hu> <20091020063555.GJ8550@elte.hu> <4ADD62AA.8060503@gmail.com> In-Reply-To: <4ADD62AA.8060503@gmail.com> X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Tue, 20 Oct 2009 07:37:49 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1155 Lines: 33 Eric Dumazet wrote: > Ingo Molnar a ?crit : > >> Still looks like a bug if it causes a breakage (linker error) on IA64, >> and if the 'fix' (i'd call it a workaround) causes a (small but nonzero) >> performance regression on other architectures. >> > > True, but this also save some amount of ram for some distro kernels. > > If we keep this static NR_CPUS thing, we might be able to free > the end of table, for other per_cpu users ? > > if (nr_cpus_ids < NR_CPUS) { > per_cpu_free_static_zone(&update_shares_data[nr_cpus_ids], > sizeof(long)*(NR_CPUS - nr_cpus_ids)); > } That's doable but Considering that the users of NR_CPUS are pretty few (and should be kept that way), I think it would be better to just use dynamic allocation, which no longer incurs any major performance difference (the only difference is constant offset vs. pointer in a variable), for those cases. Thanks. -- tejun -- 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/