From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rusty Russell Subject: Re: [patch 02/41] cpu alloc: The allocator Date: Fri, 30 May 2008 15:52:24 +1000 Message-ID: <200805301552.25423.rusty@rustcorp.com.au> References: <20080530035620.587204923@sgi.com> <483F8AF7.9000309@cosmosbay.com> 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]:48336 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754184AbYE3Fw0 (ORCPT ); Fri, 30 May 2008 01:52:26 -0400 In-Reply-To: Content-Disposition: inline Sender: linux-arch-owner@vger.kernel.org List-ID: To: Christoph Lameter Cc: Eric Dumazet , akpm@linux-foundation.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, David Miller , Peter Zijlstra , Mike Travis On Friday 30 May 2008 15:20:45 Christoph Lameter wrote: > On Fri, 30 May 2008, Eric Dumazet wrote: > > > +static DEFINE_PER_CPU(UNIT_TYPE, area[UNITS]); > > > > area[] is not guaranteed to be aligned on anything but 4 bytes. > > > > If someone then needs to call cpu_alloc(8, GFP_KERNEL, 8), it might get > > an non aligned result. > > > > Either you should add an __attribute__((__aligned__(PAGE_SIZE))), > > or take into account the real address of area[] in cpu_alloc() to avoid > > waste of up to PAGE_SIZE bytes > > per cpu. > > I think cacheline aligning should be sufficient. People should not > allocate large page aligned objects here. I vaguely recall there were issues with this in the module code. They might be gone now, but failing to meet alignment contraints without a big warning would suck. But modifying your code to consider the actual alignment is actually pretty trivial, AFAICT. Cheers, Rusty.