On Fri, 03 Nov 2023 15:45:13 +0800 "Huang, Ying" <ying.huang@xxxxxxxxx> wrote: > Gregory Price <gregory.price@xxxxxxxxxxxx> writes: > > > On Thu, Nov 02, 2023 at 10:47:33AM +0100, Michal Hocko wrote: > >> On Wed 01-11-23 12:58:55, Gregory Price wrote: > >> > Basically consider: `numactl --interleave=all ...` > >> > > >> > If `--weights=...`: when a node hotplug event occurs, there is no > >> > recourse for adding a weight for the new node (it will default to 1). > >> > >> Correct and this is what I was asking about in an earlier email. How > >> much do we really need to consider this setup. Is this something nice to > >> have or does the nature of the technology requires to be fully dynamic > >> and expect new nodes coming up at any moment? > >> > > > > Dynamic Capacity is expected to cause a numa node to change size (in > > number of memory blocks) rather than cause numa nodes to come and go, so > > maybe handling the full node hotplug is a bit of an overreach. > > Will node max bandwidth change with the number of memory blocks? Typically no as even a single memory extent would probably be interleaved across all the actual memory devices (think DIMMS for simplicity) within a CXL device. I guess a device 'could' do some scaling based on capacity provided to a particular host but feels like they should be separate controls. I don't recall there being anything in the specification to suggest the need to recheck the CDAT info for updates when DC add / remove events happen. Mind you, who knows in future :) We'll point out in relevant forums that doing so would be very hard to handle cleanly in Linux. Jonathan
