From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx146.postini.com [74.125.245.146]) by kanga.kvack.org (Postfix) with SMTP id DA8736B0002 for ; Fri, 22 Feb 2013 16:04:31 -0500 (EST) Received: by mail-pa0-f46.google.com with SMTP id kp14so677449pab.19 for ; Fri, 22 Feb 2013 13:04:31 -0800 (PST) Date: Fri, 22 Feb 2013 13:03:51 -0800 (PST) From: Hugh Dickins Subject: Re: [PATCH 2/7] ksm: treat unstable nid like in stable tree In-Reply-To: <51271A7D.6020305@gmail.com> Message-ID: References: <51271A7D.6020305@gmail.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Ric Mason Cc: Andrew Morton , Mel Gorman , Petr Holasek , Andrea Arcangeli , Izik Eidus , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Fri, 22 Feb 2013, Ric Mason wrote: > On 02/21/2013 04:20 PM, Hugh Dickins wrote: > > An inconsistency emerged in reviewing the NUMA node changes to KSM: > > when meeting a page from the wrong NUMA node in a stable tree, we say > > that it's okay for comparisons, but not as a leaf for merging; whereas > > when meeting a page from the wrong NUMA node in an unstable tree, we > > bail out immediately. > > IIUC > - ksm page from the wrong NUMA node will be add to current node's stable tree That should never happen (and when I was checking with a WARN_ON it did not happen). What can happen is that a node already in a stable tree has its page migrated away to another NUMA node. > - normal page from the wrong NUMA node will be merged to current node's > stable tree <- where I miss here? I didn't see any special handling in > function stable_tree_search for this case. nid = get_kpfn_nid(page_to_pfn(page)); root = root_stable_tree + nid; to choose the right tree for the page, and if (get_kpfn_nid(stable_node->kpfn) != NUMA(stable_node->nid)) { put_page(tree_page); goto replace; } to make sure that we don't latch on to a node whose page got migrated away. > - normal page from the wrong NUMA node will compare but not as a leaf for > merging after the patch I don't understand you there, but hope my remarks above resolve it. Hugh -- 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