From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [PATCH] percpu: add optimized generic percpu accessors Date: Wed, 21 Jan 2009 11:05:07 +0100 Message-ID: <20090121100507.GC18728@elte.hu> References: <20090115183942.GA6325@elte.hu> <200901170827.33729.rusty@rustcorp.com.au> <20090116220832.GB20653@elte.hu> <200901201328.24605.rusty@rustcorp.com.au> <20090120104022.GB29346@elte.hu> <4976B82E.1080002@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Rusty Russell , Herbert Xu , akpm@linux-foundation.org, hpa@zytor.com, brgerst@gmail.com, ebiederm@xmission.com, cl@linux-foundation.org, travis@sgi.com, linux-kernel@vger.kernel.org, steiner@sgi.com, hugh@veritas.com, "David S. Miller" , netdev@vger.kernel.org, Mathieu Desnoyers To: Tejun Heo Return-path: Received: from mx3.mail.elte.hu ([157.181.1.138]:60720 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758960AbZAUKGI (ORCPT ); Wed, 21 Jan 2009 05:06:08 -0500 Content-Disposition: inline In-Reply-To: <4976B82E.1080002@kernel.org> Sender: netdev-owner@vger.kernel.org List-ID: * Tejun Heo wrote: > Ingo Molnar wrote: > > The larger point still remains: the kernel dominantly uses static percpu > > variables by a margin of 10 to 1, so we cannot just brush away the static > > percpu variables and must concentrate on optimizing that side with > > priority. It's nice if the dynamic percpu-alloc side improves as well, of > > course. > > Well, the infrequent usage of dynamic percpu allocation is in some part > due to the poor implementation, so it's sort of chicken and egg problem. > I got into this percpu thing because I wanted a percpu reference count > which can be dynamically allocated and it sucked. Sure, but even static percpu sucked very much (it expanded to half a dozen or more instructions), and dynamic is _more_ complex. Anyway, it's getting fixed now :-) Ingo