On 09/26/2013 10:53 PM, Tejun Heo wrote: > 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 OK. Trying below: movablenode [KNL,X86] This option enables the kernel to arrange hotpluggable memory into ZONE_MOVABLE zone. If memory in a node is all hotpluggable, the option may make the whole node has only one ZONE_MOVABLE zone, so that the whole node can be hot-removed after system is up. Note that this option may cause NUMA performance down. As for the comment in cmdline_parse_movablenode(): /* * ACPI SRAT records all hotpluggable memory ranges. But before * SRAT is parsed, we don't know about it. So by specifying this * option, we will use the bottom-up mode to try allocating memory * near the kernel image before SRAT is parsed. * * Bottom-up mode prevents memblock allocating hotpluggable memory * for the kernel so that the kernel will arrange hotpluggable * memory into ZONE_MOVABLE zone when possible. */ Thanks. > more. Other than that, > > Acked-by: Tejun Heo <tj@xxxxxxxxxx> > > Thanks. > -- Thanks. Zhang Yanfei -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
