On 5/10/23 23:56, Huang Ying wrote: > To improve the scalability of the page allocation, in this series, we > will create one zone instance for each about 256 GB memory of a zone > type generally. That is, one large zone type will be split into > multiple zone instances. A few anecdotes for why I think _some_ people will like this: Some Intel hardware has a "RAM" caching mechanism. It either caches DRAM in High-Bandwidth Memory or Persistent Memory in DRAM. This cache is direct-mapped and can have lots of collisions. One way to prevent collisions is to chop up the physical memory into cache-sized zones and let users choose to allocate from one zone. That fixes the conflicts. Some other Intel hardware a ways to chop a NUMA node representing a single socket into slices. Usually one slice gets a memory controller and its closest cores. Intel calls these approaches Cluster on Die or Sub-NUMA Clustering and users can select it from the BIOS. In both of these cases, users have reported scalability improvements. We've gone as far as to suggest the socket-splitting options to folks today who are hitting zone scalability issues on that hardware. That said, those _same_ users sometimes come back and say something along the lines of: "So... we've got this app that allocates a big hunk of memory. It's going slower than before." They're filling up one of the chopped-up zones, hitting _some_ kind of undesirable reclaim behavior and they want their humpty-dumpty zones put back together again ... without hurting scalability. Some people will never be happy. :) Anyway, _if_ you do this, you might also consider being able to dynamically adjust a CPU's zonelists somehow. That would relieve pressure on one zone for those uneven allocations. That wasn't an option in the two cases above because users had ulterior motives for sticking inside a single zone. But, in your case, the zones really do have equivalent performance.
