From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [PATCH] Make dynamic/run-time configuration of zonelist order configurable From: Lee Schermerhorn In-Reply-To: <20070530112119.efa977fe.kamezawa.hiroyu@jp.fujitsu.com> References: <1180468121.5067.64.camel@localhost> <20070530112119.efa977fe.kamezawa.hiroyu@jp.fujitsu.com> Content-Type: text/plain Date: Wed, 30 May 2007 11:52:01 -0400 Message-Id: <1180540321.5850.6.camel@localhost> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: KAMEZAWA Hiroyuki Cc: linux-mm@kvack.org, akpm@linux-foundation.org, nacc@us.ibm.com List-ID: On Wed, 2007-05-30 at 11:21 +0900, KAMEZAWA Hiroyuki wrote: > On Tue, 29 May 2007 15:48:41 -0400 > Lee Schermerhorn wrote: > > > Signed-off-by: Lee Schermerhorn > > > > no problem was found on my ia64 test box. > > But one point.. > > > -#ifdef CONFIG_NUMA > > +#ifdef CONFIG_DYNAMIC_ZONELIST_ORDER > > { > > .ctl_name = CTL_UNNUMBERED, > > .procname = "numa_zonelist_order", > > non-NUMA, memory-hotpluggable machine need this control ?? > Hi, Kame: Here was my thinking on that point--actually on the numa_zonelist_order sysctl in general: When would it ever be needed? I think the answer is when the dynamic configuration didn't "get it right" and you want to fix it w/o reboot. I agree that it is very likely that you wouldn't want to reboot if you've gone to all the trouble to support memory hotplug. In that case, we have a couple of choices: 1) just enable the config option manually for platforms that support memory hotplug, or 2) make the option default to 'y' when memory hotplug is configured. As I tried to indicate in the patch description, because some smallish systems appear to use NUMA emulation for resource management, they must enable NUMA support. However, they may not [I think probably not] need run-time zoneorder configuration. I suspect those platforms don't support memory hotplug at this time either. Now, the code in question [sysctl and build_zonelist functions] may be relatively small--i.e., less than a page. But, it all adds up, so I offered a way for small systems that still wanted NUMA support to get back what we took from them with the zonelist order patches. Thoughts? 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