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I actually have a patch series in my backlog = to > introduce NUMA-balancing support in sched_ext. It makes NUMA hinting scan= s > opt-in for BPF schedulers and exposes a task's preferred NUMA node to BPF= . That is great news, thanks. My patch was only a small sketch to show the problem, so I am happy to leave it at that and follow your series instead. Opt-in scanning plus the preferred node exposed to BPF sounds like what I was looking for. My scheduler runs on KVM hypervisors and reads p->numa_preferred_nid to choose a home node for each vCPU thread, falling back to the thread group's majority when a task has none. Under SCX that value stops being updated, which is how I noticed. > It also lets a BPF scheduler set a per-task memory target, which NUMA bal= ancing > can use when migrating pages after hinting faults. This part sounds interesting too. Guests that span two nodes are the hard case for me: today I can only follow the memory, I cannot ask for it to follow the vCPUs. > I can probably send the patch series at this point, it's not completely > well-tested, but it might be useful to have it on the list, so that we ca= n start > discussing and improving it. I'll keep you in the loop. Thanks, I will be watching for it. If it is of any use, I can try it on a few hypervisors (2- and 4-node hosts) and share numbers for scan rate, hint faults and time spent on the preferred node. Thanks, Vladimir