From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rusty Russell Subject: Re: [patch 04/41] cpu ops: Core piece for generic atomic per cpu operations Date: Thu, 12 Jun 2008 12:44:11 +1000 Message-ID: <200806121244.12173.rusty@rustcorp.com.au> References: <20080530035620.587204923@sgi.com> <200806121058.02125.nickpiggin@yahoo.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from ozlabs.org ([203.10.76.45]:54128 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751748AbYFLCoX (ORCPT ); Wed, 11 Jun 2008 22:44:23 -0400 In-Reply-To: <200806121058.02125.nickpiggin@yahoo.com.au> Content-Disposition: inline Sender: linux-arch-owner@vger.kernel.org List-ID: To: Nick Piggin Cc: Christoph Lameter , Andrew Morton , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, David Miller , Eric Dumazet , Peter Zijlstra , Mike Travis , Martin Peschke On Thursday 12 June 2008 10:58:01 Nick Piggin wrote: > On Thursday 12 June 2008 09:39, Christoph Lameter wrote: > > On Wed, 11 Jun 2008, Rusty Russell wrote: > > > > 4. The modeling of local_t on atomic_t limits it to 32bit! > > > > > > Again wrong. And adding an exclamation mark doesn't make it true. > > > > Ewww ... Its atomic_long_t ahh. Ok then there no 32 bit support. What > > about pointers? > > sizeof(long) == sizeof(void *) in Linux, right? > > If you were to support just a single data type, long would probably > be the most useful. Still, it might be more consistent to support > int and long, same as atomic. Sure, but in practice these tend to be simple counters: that could well change when dynamic percpu allocs become first class citizens, but let's not put the cart before the horse... Per-cpu seems to be particularly prone to over-engineering: see commit 7ff6f08295d90ab20d25200ef485ebb45b1b8d71 from almost two years ago. Grepping here reveals that this infrastructure is still not used. Cheers, Rusty.