On Mon 12-06-17 12:28:32, Wei Yang wrote: > On Thu, Jun 08, 2017 at 02:23:18PM +0200, Michal Hocko wrote: > >From: Michal Hocko <mhocko@xxxxxxxx> > > > >movable_node kernel parameter allows to make hotplugable NUMA > >nodes to put all the hotplugable memory into movable zone which > >allows more or less reliable memory hotremove. At least this > >is the case for the NUMA nodes present during the boot (see > >find_zone_movable_pfns_for_nodes). > > > > When movable_node is enabled, we would have overlapped zones, right? It won't based on this patch. See movable_pfn_range > To be specific, only ZONE_MOVABLE could have memory ranges belongs to other > zones. > > This looks a little different in the whole ZONE design. > > >This is not the case for the memory hotplug, though. > > > > echo online > /sys/devices/system/memory/memoryXYZ/status > > > >will default to a kernel zone (usually ZONE_NORMAL) unless the > >particular memblock is already in the movable zone range which is not > ^^^ > > Here is memblock or a memory_block? yes > > >the case normally when onlining the memory from the udev rule context > >for a freshly hotadded NUMA node. The only option currently is to have a > > So the semantic you want to change here is to make the memory_block in > ZONE_MOVABLE when movable_node is enabled. Yes, by default when there the specific range is not associated with any other zone. > Besides this, movable_node is enabled, what other requirements? Like, this > memory_block should next to current ZONE_MOVABLE ? or something else? no other requirements. > >special udev rule to echo online_movable to all memblocks belonging to > >such a node which is rather clumsy. Not the mention this is inconsistent > ^^^ > > Hmm... "Not to mentions" looks more understandable. yes this is a typo > BTW, I am not a native speaker. If this usage is correct, just ignore this > comment. > > >as well because what ended up in the movable zone during the boot will > >end up in a kernel zone after hotremove & hotadd without special care. > > > >It would be nice to reuse memblock_is_hotpluggable but the runtime > >hotplug doesn't have that information available because the boot and > >hotplug paths are not shared and it would be really non trivial to > >make them use the same code path because the runtime hotplug doesn't > >play with the memblock allocator at all. > > > >Teach move_pfn_range that MMOP_ONLINE_KEEP can use the movable zone if > >movable_node is enabled and the range doesn't overlap with the existing > >normal zone. This should provide a reasonable default onlining strategy. > > > >Strictly speaking the semantic is not identical with the boot time > >initialization because find_zone_movable_pfns_for_nodes covers only the > >hotplugable range as described by the BIOS/FW. From my experience this > >is usually a full node though (except for Node0 which is special and > >never goes away completely). If this turns out to be a problem in the > >real life we can tweak the code to store hotplug flag into memblocks > >but let's keep this simple now. > > > > Let me try to understand your purpose of this change. > > If a memblock has MEMBLOCK_HOTPLU set, it would be in ZONE_MOVABLE during > bootup. While a hotplugged memory_block would be in ZONE_NORMAL without > special care. > > So you want to make sure when movable_node is enabled, the hotplugged > memory_block would be in ZONE_MOVABLE. Is this correct? yes > One more thing is do we have MEMBLOCK_HOTPLU for a hotplugged memory_block? No, we do not, as the changelog mentions. This flag is set in the memblock allocator (do not confuse that with the memory_block hotplug works with - yeah quite confusing) and that is a boot only thing. We do not use it during runtime memory hotplug. -- Michal Hocko SUSE Labs -- 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>
