On 09/09/2016 07:06 PM, Michal Hocko wrote: > On Thu 08-09-16 08:16:58, Anshuman Khandual wrote: >> > Each individual node in the system has a ZONELIST_FALLBACK zonelist >> > and a ZONELIST_NOFALLBACK zonelist. These zonelists decide fallback >> > order of zones during memory allocations. Sometimes it helps to dump >> > these zonelists to see the priority order of various zones in them. >> > >> > Particularly platforms which support memory hotplug into previously >> > non existing zones (at boot), this interface helps in visualizing >> > which all zonelists of the system at what priority level, the new >> > hot added memory ends up in. POWER is such a platform where all the >> > memory detected during boot time remains with ZONE_DMA for good but >> > then hot plug process can actually get new memory into ZONE_MOVABLE. >> > So having a way to get the snapshot of the zonelists on the system >> > after memory or node hot[un]plug is desirable. This change adds one >> > new sysfs interface (/sys/devices/system/memory/system_zone_details) >> > which will fetch and dump this information. > I am still not sure I understand why this is helpful and who is the > consumer for this interface and how it will benefit from the > information. Dave (who doesn't seem to be on the CC list re-added) had > another objection that this breaks one-value-per-file rule for sysfs > files. It helps in understanding the relative priority of each memory zone of the system during various allocation scenarios. Its particularly helpful after hotplug/unplug of additional memory into previously non existing zone on a node. > > This all smells like a debugging feature to me and so it should go into > debugfs. Sure, will make it a debugfs interface. -- 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>