On Thu, Jun 04, 2020 at 01:00:55PM -0700, Dave Hansen wrote: > On 6/4/20 11:12 AM, Daniel Jordan wrote: > >> E.g., on powerpc that's 16MB so they have *a lot* of memory blocks. > >> That's why that's not papering over the problem. Increasing the memory > >> block size isn't always the answer. > > Ok. If you don't mind, what's the purpose of hotplugging at that granularity? > > I'm simply curious. > > FWIW, the 128MB on x86 came from the original sparsemem/hotplug > implementation. It was the size of the smallest DIMM that my server > system at the time would take. ppc64's huge page size was and is 16MB > and that's also the granularity with which hypervisors did hot-add way > back then. I'm not actually sure what they do now. Interesting, that tells me a lot more than the "matt - 128 is convenient right now" comment that has always weirdly stuck out at me. > I actually can't think of anything that's *keeping* it at 128MB on x86 > though. We don't, for instance, require a whole section to be > pfn_valid(). Hm, something to look into.
