From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Travis Subject: Re: [patch 00/41] cpu alloc / cpu ops v3: Optimize per cpu access Date: Fri, 30 May 2008 07:38:33 -0700 Message-ID: <48401169.3050706@sgi.com> References: <20080530035620.587204923@sgi.com> <20080529215827.b659d032.akpm@linux-foundation.org> <20080529222143.5d7aa1e5.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from netops-testserver-3-out.sgi.com ([192.48.171.28]:54256 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752007AbYE3Oig (ORCPT ); Fri, 30 May 2008 10:38:36 -0400 In-Reply-To: Sender: linux-arch-owner@vger.kernel.org List-ID: To: Christoph Lameter Cc: Andrew Morton , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, David Miller , Eric Dumazet , Peter Zijlstra , Rusty Russell Christoph Lameter wrote: > On Thu, 29 May 2008, Andrew Morton wrote: ... >> Plus who knows what lies ahead of us? > > Well invariably we will end up with cpu area defragmentation.... Sigh. > >> I don't think there is presently any upper limit on alloc_percpu()? It >> uses kmalloc() and kmalloc_node()? >> >> Even if there is some limit, is it an unfixable one? > > No there is no limit. It just wastes lots of space (pointer arrays, > alignment etc) that we could use to configure sufficiently large per cpu > areas. Is there any reason why the per_cpu area couldn't be made extensible? Maybe a simple linked list of available areas? (And use a config variable and/or boot param for initial size and increment size?) [Ignoring the problem of reclaiming the space...]