From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id F0FB36B010F for ; Mon, 21 Sep 2009 09:31:43 -0400 (EDT) Received: by bwz24 with SMTP id 24so2036350bwz.38 for ; Mon, 21 Sep 2009 06:31:42 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20090921130440.GN12726@csn.ul.ie> References: <1253302451-27740-1-git-send-email-mel@csn.ul.ie> <1253302451-27740-2-git-send-email-mel@csn.ul.ie> <84144f020909200145w74037ab9vb66dae65d3b8a048@mail.gmail.com> <4AB5FD4D.3070005@kernel.org> <4AB5FFF8.7000602@cs.helsinki.fi> <4AB6508C.4070602@kernel.org> <4AB739A6.5060807@in.ibm.com> <20090921084248.GC12726@csn.ul.ie> <20090921130440.GN12726@csn.ul.ie> Date: Mon, 21 Sep 2009 16:31:42 +0300 Message-ID: <84144f020909210631h23bf3292q1d87c063c7b5c126@mail.gmail.com> Subject: Re: [PATCH 1/3] slqb: Do not use DEFINE_PER_CPU for per-node data From: Pekka Enberg Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: Sachin Sant , Tejun Heo , Nick Piggin , Christoph Lameter , heiko.carstens@de.ibm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Benjamin Herrenschmidt List-ID: On Mon, Sep 21, 2009 at 4:04 PM, Mel Gorman wrote: >> The "per-cpu" area in this case is actually a per-node area. This implied that >> it was either racing (but the locking looked sound), a buffer overflow (but >> I couldn't find one) or the per-cpu areas were being written to by something >> else unrelated. > > This latter guess was close to the mark but not for the reasons I was > guessing. There isn't magic per-cpu-area-freeing going on. Once I examined > the implementation of per-cpu data, it was clear that the per-cpu areas for > the node IDs were never being allocated in the first place on PowerPC. It's > probable that this never worked but that it took a long time before SLQB > was run on a memoryless configuration. > > This patch would replace patch 1 of the first hatchet job I did. It's possible > a similar patch is needed for S390. I haven't looked at the implementation > there and I don't have a means of testing it. Other architectures could be affected as well which makes me think "hatchet job number one" is the way forward. Nick? Pekka -- 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