From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [PATCH] Memoryless nodes: use "node_memory_map" for cpuset mems_allowed validation From: Lee Schermerhorn In-Reply-To: <20070723190922.GA6036@us.ibm.com> References: <20070711182219.234782227@sgi.com> <20070711182250.005856256@sgi.com> <1184964564.9651.66.camel@localhost> <20070723190922.GA6036@us.ibm.com> Content-Type: text/plain Date: Mon, 23 Jul 2007 16:59:52 -0400 Message-Id: <1185224393.23917.6.camel@localhost> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Nishanth Aravamudan Cc: Christoph Lameter , Paul Jackson , akpm@linux-foundation.org, kxr@sgi.com, linux-mm@kvack.org, KAMEZAWA Hiroyuki List-ID: On Mon, 2007-07-23 at 12:09 -0700, Nishanth Aravamudan wrote: > On 20.07.2007 [16:49:24 -0400], Lee Schermerhorn wrote: > > This fixes a problem I encountered testing Christoph's memoryless nodes > > series. Applies atop that series. Other than this, series holds up > > under what testing I've been able to do this week. > > > > Memoryless Nodes: use "node_memory_map" for cpusets mems_allowed validation > > > > cpusets try to ensure that any node added to a cpuset's > > mems_allowed is on-line and contains memory. The assumption > > was that online nodes contained memory. Thus, it is possible > > to add memoryless nodes to a cpuset and then add tasks to this > > cpuset. This results in continuous series of oom-kill and other > > console stack traces and apparent system hang. > > > > Change cpusets to use node_states[N_MEMORY] [a.k.a. > > node_memory_map] in place of node_online_map when vetting > > memories. Return error if admin attempts to write a non-empty > > mems_allowed node mask containing only memoryless-nodes. > > > > Signed-off-by: Lee Schermerhorn > > Lee, while looking at this change, I think it ends up fixing > cpuset_mems_allowed() to return nodemasks that only include nodes in > node_states[N_MEMORY]. However, cpuset_current_mems_allowed is a > lockless macro which would still be broken. I think it would need to > becom a static inline nodes_and() in the CPUSET case and a #define > node_states[N_MEMORY] in the non-CPUSET case? > > Or perhaps we should adjust cpusets to make it so that the mems_allowed > member only includes nodes that are set in node_states[N_MEMORY]? I thought that's what my patch to nodelist_parse() did. It ensures that current->mems_allowed is correct [contains at least one node with memory, and only nodes with memory] at the time it is installed, but doesn't consider memory hot plug and node off-lining. Is this [offline/hotplug] your point? Seems like that is an issue that exists in the unpatched code as well--i.e., unlike cpuset_mems_allowed(), the lockless, "_current_" version does not vet current->mems_allowed against the nodes_online_mask. So, all valid nodes in current->mems_allowed could have been off-lined since the mask was installed. Am I reading this right? Lee -- 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