Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934531AbZDBCXk (ORCPT ); Wed, 1 Apr 2009 22:23:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756021AbZDBCXa (ORCPT ); Wed, 1 Apr 2009 22:23:30 -0400 Received: from smtp.ultrahosting.com ([74.213.174.254]:55892 "EHLO smtp.ultrahosting.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755411AbZDBCXa (ORCPT ); Wed, 1 Apr 2009 22:23:30 -0400 Date: Wed, 1 Apr 2009 22:18:59 -0400 (EDT) From: Christoph Lameter X-X-Sender: cl@qirst.com To: Ingo Molnar cc: Linus Torvalds , Tejun Heo , Martin Schwidefsky , rusty@rustcorp.com.au, tglx@linutronix.de, x86@kernel.org, linux-kernel@vger.kernel.org, hpa@zytor.com, Paul Mundt , rmk@arm.linux.org.uk, starvik@axis.com, ralf@linux-mips.org, davem@davemloft.net, cooloney@kernel.org, kyle@mcmartin.ca, matthew@wil.cx, grundler@parisc-linux.org, takata@linux-m32r.org, benh@kernel.crashing.org, rth@twiddle.net, ink@jurassic.park.msu.ru, heiko.carstens@de.ibm.com, Nick Piggin , Peter Zijlstra Subject: Re: [PATCH UPDATED] percpu: use dynamic percpu allocator as the default percpu allocator In-Reply-To: <20090401223241.GA28168@elte.hu> Message-ID: References: <49D099F0.3000807@kernel.org> <20090330114938.GB10070@elte.hu> <49D2B209.9060000@kernel.org> <20090401154913.GA31435@elte.hu> <20090401190113.GA734@elte.hu> <20090401223241.GA28168@elte.hu> 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: 732 Lines: 18 On Thu, 2 Apr 2009, Ingo Molnar wrote: > So ... we regressed the performance of percpu_free(NULL) with a > potential cross-CPU cacheline bounce. Without the patch, > percpu_free(NULL) would never do such a bounce. So i dont think the > patch is a good idea. But percpu_free is not an operation typical for hot code paths. Per cpu variables are allocated and freed in rarely used code paths. Typically the use of the per cpu variables occurs in hot code paths, not their allocations. -- 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/