Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755151AbZI3Xyl (ORCPT ); Wed, 30 Sep 2009 19:54:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755131AbZI3Xyl (ORCPT ); Wed, 30 Sep 2009 19:54:41 -0400 Received: from smtp2.ultrahosting.com ([74.213.174.253]:43024 "EHLO smtp.ultrahosting.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754990AbZI3Xyk (ORCPT ); Wed, 30 Sep 2009 19:54:40 -0400 Date: Wed, 30 Sep 2009 19:49:50 -0400 (EDT) From: Christoph Lameter X-X-Sender: cl@gentwo.org To: Peter Chubb cc: "Luck, Tony" , Tejun Heo , Nick Piggin , "Yu, Fenghua" , linux-ia64 , Ingo Molnar , Rusty Russell , "linux-kernel@vger.kernel.org" Subject: Re: [PATCHSET percpu#for-next] percpu: convert ia64 to dynamic percpu and drop the old one, take#2 In-Reply-To: <87hbukxcau.wl%peter@chubb.wattle.id.au> Message-ID: References: <1253682382-24740-1-git-send-email-tj@kernel.org> <4AC153EA.2050007@suse.de> <57C9024A16AD2D4C97DC78E552063EA3E2F03E58@orsmsx505.amr.corp.intel.com> <57C9024A16AD2D4C97DC78E552063EA3E2F03FDC@orsmsx505.amr.corp.intel.com> <87hbukxcau.wl%peter@chubb.wattle.id.au> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1066 Lines: 24 On Thu, 1 Oct 2009, Peter Chubb wrote: > r3, r4 and r5 are currently unused by the kernel, and unused > by GCC and ICC. Only hand-written assembler and weird compilers use > those registers(and my virtual-machine monitor :-(). If you wanted to > experiment, that'd be a starting place. > > I'm not sure of the advantage though -- TLB mapping is relatively > cheap, and we're no longer hard-wiring the translation register. Dynamic and static per cpu variables could use relative access to that register. This would reduce code size, avoid the use of a TLB entry. > You';d have to do somne careful benchmarking on a wide variety of > workloads and machines to get a definitive answer. I have some patches here that make heavy use of dynamic percpu allocations in the allocators to optimize the alloc / free paths. -- 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/