From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id 181D96B004D for ; Mon, 21 Sep 2009 20:02:35 -0400 (EDT) Message-ID: <4AB813F3.8060102@kernel.org> Date: Tue, 22 Sep 2009 09:01:55 +0900 From: Tejun Heo MIME-Version: 1.0 Subject: Re: [PATCH 1/3] powerpc: Allocate per-cpu areas for node IDs for SLQB to use as per-node areas References: <1253549426-917-1-git-send-email-mel@csn.ul.ie> <1253549426-917-2-git-send-email-mel@csn.ul.ie> In-Reply-To: <1253549426-917-2-git-send-email-mel@csn.ul.ie> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: Nick Piggin , Pekka Enberg , Christoph Lameter , heiko.carstens@de.ibm.com, sachinp@in.ibm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Benjamin Herrenschmidt List-ID: Hello, Mel Gorman wrote: > diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c > index 1f68160..a5f52d4 100644 > --- a/arch/powerpc/kernel/setup_64.c > +++ b/arch/powerpc/kernel/setup_64.c > @@ -588,6 +588,26 @@ void __init setup_per_cpu_areas(void) > paca[i].data_offset = ptr - __per_cpu_start; > memcpy(ptr, __per_cpu_start, __per_cpu_end - __per_cpu_start); > } > +#ifdef CONFIG_SLQB > + /* > + * SLQB abuses DEFINE_PER_CPU to setup a per-node area. This trick > + * assumes that ever node ID will have a CPU of that ID to match. > + * On systems with memoryless nodes, this may not hold true. Hence, > + * we take a second pass initialising a "per-cpu" area for node-ids > + * that SLQB can use > + */ > + for_each_node_state(i, N_NORMAL_MEMORY) { > + > + /* Skip node IDs that a valid CPU id exists for */ > + if (paca[i].data_offset) > + continue; > + > + ptr = alloc_bootmem_pages_node(NODE_DATA(cpu_to_node(i)), size); > + > + paca[i].data_offset = ptr - __per_cpu_start; > + memcpy(ptr, __per_cpu_start, __per_cpu_end - __per_cpu_start); > + } > +#endif /* CONFIG_SLQB */ > } > #endif Eh... I don't know. This seems too hacky to me. Why not just allocate pointer array of MAX_NUMNODES and allocate per-node memory there? This will be slightly more expensive but I doubt it will be noticeable. The only extra overhead is the cachline footprint for the extra array. Thanks. -- tejun -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org