From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tang Chen Date: Thu, 31 Jan 2013 07:10:50 +0000 Subject: Re: [PATCH v6 00/15] memory-hotplug: hot-remove physical memory Message-Id: <510A18FA.2010107@cn.fujitsu.com> List-Id: References: <1357723959-5416-1-git-send-email-tangchen@cn.fujitsu.com> <1359463973.1624.15.camel@kernel> <5108F2B3.3090506@cn.fujitsu.com> <1359595344.1557.13.camel@kernel> <5109E59F.5080104@cn.fujitsu.com> <1359613162.1587.0.camel@kernel> In-Reply-To: <1359613162.1587.0.camel@kernel> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Simon Jeons Cc: akpm@linux-foundation.org, rientjes@google.com, len.brown@intel.com, benh@kernel.crashing.org, paulus@samba.org, cl@linux.com, minchan.kim@gmail.com, kosaki.motohiro@jp.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com, wujianguo@huawei.com, wency@cn.fujitsu.com, hpa@zytor.com, linfeng@cn.fujitsu.com, laijs@cn.fujitsu.com, mgorman@suse.de, yinghai@kernel.org, glommer@parallels.com, x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-acpi@vger.kernel.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, linux-ia64@vger.kernel.org, cmetcalf@tilera.com, sparclinux@vger.kernel.org On 01/31/2013 02:19 PM, Simon Jeons wrote: > Hi Tang, > On Thu, 2013-01-31 at 11:31 +0800, Tang Chen wrote: >> Hi Simon, >> >> Please see below. :) >> >> On 01/31/2013 09:22 AM, Simon Jeons wrote: >>> >>> Sorry, I still confuse. :( >>> update node_states[N_NORMAL_MEMORY] to node_states[N_MEMORY] or >>> node_states[N_NORMAL_MEMOR] present 0...ZONE_MOVABLE? >>> >>> node_states is what? node_states[N_NORMAL_MEMOR] or >>> node_states[N_MEMORY]? >> >> Are you asking what node_states[] is ? >> >> node_states[] is an array of nodemask, >> >> extern nodemask_t node_states[NR_NODE_STATES]; >> >> For example, node_states[N_NORMAL_MEMOR] represents which nodes have >> normal memory. >> If N_MEMORY = N_HIGH_MEMORY = N_NORMAL_MEMORY, node_states[N_MEMORY] is >> node_states[N_NORMAL_MEMOR]. So it represents which nodes have 0 ... >> ZONE_MOVABLE. >> > > Sorry, how can nodes_state[N_NORMAL_MEMORY] represents a node have 0 ... > *ZONE_MOVABLE*, the comment of enum nodes_states said that > N_NORMAL_MEMORY just means the node has regular memory. > Hi Simon, Let's say it in this way. If we don't have CONFIG_HIGHMEM, N_HIGH_MEMORY = N_NORMAL_MEMORY. We don't have a separate macro to represent highmem because we don't have highmem. This is easy to understand, right ? Now, think it just like above: If we don't have CONFIG_MOVABLE_NODE, N_MEMORY = N_HIGH_MEMORY = N_NORMAL_MEMORY. This means we don't allow a node to have only movable memory, not we don't have movable memory. A node could have normal memory and movable memory. So nodes_state[N_NORMAL_MEMORY] represents a node have 0 ... *ZONE_MOVABLE*. I think the point is: CONFIG_MOVABLE_NODE means we allow a node to have only movable memory. So without CONFIG_MOVABLE_NODE, it doesn't mean a node cannot have movable memory. It means the node cannot have only movable memory. It can have normal memory and movable memory. 1) With CONFIG_MOVABLE_NODE: N_NORMAL_MEMORY: nodes who have normal memory. normal memory only normal and highmem normal and highmem and movablemem normal and movablemem N_MEMORY: nodes who has memory (any memory) normal memory only normal and highmem normal and highmem and movablemem normal and movablemem ---------------- We can have movablemem. highmem only ------------------------- highmem and movablemem --------------- movablemem only ---------------------- We can have movablemem only. *** 2) With out CONFIG_MOVABLE_NODE: N_MEMORY = N_NORMAL_MEMORY: (Here, I omit N_HIGH_MEMORY) normal memory only normal and highmem normal and highmem and movablemem normal and movablemem ---------------- We can have movablemem. No movablemem only ------------------- We cannot have movablemem only. *** The semantics is not that clear here. So we can only try to understand it from the code where we use N_MEMORY. :) That is my understanding of this. Thanks. :)