Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752265AbZJTN5f (ORCPT ); Tue, 20 Oct 2009 09:57:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751460AbZJTN5d (ORCPT ); Tue, 20 Oct 2009 09:57:33 -0400 Received: from hera.kernel.org ([140.211.167.34]:42605 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751232AbZJTN5c (ORCPT ); Tue, 20 Oct 2009 09:57:32 -0400 Message-ID: <4ADDC1FC.8010903@kernel.org> Date: Tue, 20 Oct 2009 22:58:20 +0900 From: Tejun Heo User-Agent: Thunderbird 2.0.0.23 (X11/20090817) MIME-Version: 1.0 To: Ingo Molnar CC: Jeff Mahoney , Jiri Kosina , Peter Zijlstra , Linux Kernel Mailing List , Tony Luck , Fenghua Yu , linux-ia64@vger.kernel.org, Linus Torvalds , Christoph Lameter 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> <4ADDB640.4020707@suse.com> <20091020134308.GA3930@elte.hu> <4ADDC1C6.9090305@kernel.org> In-Reply-To: <4ADDC1C6.9090305@kernel.org> X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Tue, 20 Oct 2009 13:57:08 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1800 Lines: 40 Of course I forgot to actually cc. Cc'ing and quoting whole body. Sorry. Tejun Heo wrote: > Ingo Molnar wrote: >> IA64 should be fixed really - we can get past the 64K of percpu data >> limit anytime we add a few more pages of per-cpu data to the kernel - >> the scheduler just happened to be the one to cross it this time. > > Christoph (cc'd hi!) was talking about re-purposing one of reserved > generic registers (for current or something, I don't remember the > details) for percpu base and just getting the original one via percpu > access. With that we should be able to lift the limitation without > much performance penalty. > >> Saying that all static percpu data must be below 64K, which will only be >> noticed once IA64 gets its testing act together months after it's been >> created is silly. If you want to enforce such a limit make it testable >> in a _timely_ fashion. Or fix the limit really. > > Yeah, the problem probably was that it only pushes the perpcu area > very slightly over the limit depending on configuration so it's not > too surprising that it didn't get reported for some time. Also, the > linker script thing is a sanity check which is intentionally put there > to trigger when this happens so that it can be found out clearly > during build time. > > In the long term, it will be a good idea to lift that restriction. > That said, I really don't think we should be adding NR_CPUS sized > array to percpu area either. Things like that quickly become very > scary with N*1024 cpu configurations. -- 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/