On Wed, Sep 25, 2013 at 02:35:14AM +0800, Zhang Yanfei wrote: > From: Tang Chen <tangchen@xxxxxxxxxxxxxx> > > The hot-Pluggable field in SRAT specifies which memory is hotpluggable. > As we mentioned before, if hotpluggable memory is used by the kernel, > it cannot be hot-removed. So memory hotplug users may want to set all > hotpluggable memory in ZONE_MOVABLE so that the kernel won't use it. > > Memory hotplug users may also set a node as movable node, which has > ZONE_MOVABLE only, so that the whole node can be hot-removed. > > But the kernel cannot use memory in ZONE_MOVABLE. By doing this, the > kernel cannot use memory in movable nodes. This will cause NUMA > performance down. And other users may be unhappy. > > So we need a way to allow users to enable and disable this functionality. > In this patch, we introduce movablenode boot option to allow users to > choose to not to consume hotpluggable memory at early boot time and > later we can set it as ZONE_MOVABLE. > > To achieve this, the movablenode boot option will control the memblock > allocation direction. That said, after memblock is ready, before SRAT is > parsed, we should allocate memory near the kernel image as we explained > in the previous patches. So if movablenode boot option is set, the kernel > does the following: > > 1. After memblock is ready, make memblock allocate memory bottom up. > 2. After SRAT is parsed, make memblock behave as default, allocate memory > top down. > > Users can specify "movablenode" in kernel commandline to enable this > functionality. For those who don't use memory hotplug or who don't want > to lose their NUMA performance, just don't specify anything. The kernel > will work as before. > > Suggested-by: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > Signed-off-by: Tang Chen <tangchen@xxxxxxxxxxxxxx> > Signed-off-by: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx> I hope the param description and comment were better. Not necessarily longer, but clearer, so it'd be great if you can polish them a bit more. Other than that, Acked-by: Tejun Heo <tj@xxxxxxxxxx> Thanks. -- tejun -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>