On Tue, Feb 13, 2018 at 03:43:26PM +0100, Peter Zijlstra wrote: > > > > Well, it was deliberate. While it's possible to be on the same memory > > node and not sharing cache, the scheduler typically is more concerned with > > the LLC than NUMA per-se. If they share LLC, then I also assume that they > > share memory locality. > > True, but the remaining code only has effect for numa balance, which is > concerned with nodes. So I don't see the point of using something > potentially smaller. > > Suppose someone did hardware where a node has 2 cache clusters, then > we'd still set a wake_affine back-off for numa-balance, even though it > remains on the same node. > > How would that be useful?
Fair point, it could be unexpected from a NUMA balancing perspective and sub-numa clustering does exist so it's a potential issue. I'm happy to change it to cpu_to_node. I can resend the series if you prefer but feel free to change it in-place if you're picking it up. I do not expect any change on the machines I tested with as for all of them LLC was equivalent to checking the node ID. -- Mel Gorman SUSE Labs
