From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Date: Thu, 17 Jan 2013 13:05:09 +0000 Subject: Re: [PATCH v3 1/2] memory-hotplug: introduce CONFIG_HAVE_BOOTMEM_INFO_NODE and revert register_page_ Message-Id: <20130117130509.GE20538@dhcp22.suse.cz> List-Id: References: <1358324059-9608-1-git-send-email-linfeng@cn.fujitsu.com> <1358324059-9608-2-git-send-email-linfeng@cn.fujitsu.com> <20130116141436.GE343@dhcp22.suse.cz> <50F7D456.9000904@cn.fujitsu.com> In-Reply-To: <50F7D456.9000904@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Lin Feng Cc: akpm@linux-foundation.org, linux-mm@kvack.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, jbeulich@suse.com, dhowells@redhat.com, wency@cn.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com, paul.gortmaker@windriver.com, laijs@cn.fujitsu.com, kamezawa.hiroyu@jp.fujitsu.com, mel@csn.ul.ie, minchan@kernel.org, aquini@redhat.com, jiang.liu@huawei.com, tony.luck@intel.com, fenghua.yu@intel.com, benh@kernel.crashing.org, paulus@samba.org, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, davem@davemloft.net, michael@ellerman.id.au, gerald.schaefer@de.ibm.com, gregkh@linuxfoundation.org, x86@kernel.org, linux390@de.ibm.com, linux-ia64@vger.kernel.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, tangchen@cn.fujitsu.com On Thu 17-01-13 18:37:10, Lin Feng wrote: [...] > > I am still not sure I understand the relation to MEMORY_HOTREMOVE. > > Is register_page_bootmem_info_node required/helpful even if > > !CONFIG_MEMORY_HOTREMOVE? > From old kenrel's view register_page_bootmem_info_node() is defined in > CONFIG_MEMORY_HOTPLUG_SPARSE, it registers some info for > memory hotplug/remove. If we don't use MEMORY_HOTPLUG feature, this > function is empty, we don't need the info at all. > So this info is not required/helpful if !CONFIG_MEMORY_HOTREMOVE. OK, then I suggest moving it under CONFIG_MEMORY_HOTREMOVE guards rather than CONFIG_MEMORY_HOTPLUG. > > Also, now that I am thinking about that more, maybe it would > > be cleaner to put the select into arch/x86/Kconfig and do it > > same as ARCH_ENABLE_MEMORY_{HOTPLUG,HOTREMOVE} (and name it > > ARCH_HAVE_BOOTMEM_INFO_NODE). > > > Maybe put it in mm/Kconfig is a better choice, because if one day > someone implements the register_page_bootmem_info_node() for other > archs they will get some clues here, that's it has been implemented on > x86_64. > But I'm not so sure... My understanding is that doing that in arch code is more appropriate because it makes the generic code less complicated. But I do not have any strong opinion on that. Looking at other ARCH_ENABLE_MEMORY_HOTPLUG and others suggests that we should be consistent with that. Thanks! -- Michal Hocko SUSE Labs