Hello, On Tue, Oct 16, 2018 at 03:37:15PM -0700, Andrew Morton wrote: > we'll still make it into 4.19.1. Am reluctant to merge this while > discussion, testing and possibly more development are ongoing. I think there can be definitely more developments primarily to make the compact deferred logic NUMA aware. Instead of a global deferred logic, we should split it per zone per node so that it backs off exponentially with an higher cap in remote nodes. The current global "backoff" limit will still apply to the "local" zone compaction. Who would like to work on that? However I don't think it's worth waiting for that, because it's not a trivial change. Certainly we can't ship upstream in production with this bug, so if it doesn't get fixed upstream we'll fix it downstream first until the more developments are production ready. This was a severe regression compared to previous kernels that made important workloads unusable and it starts when __GFP_THISNODE was added to THP allocations under MADV_HUGEPAGE. It is not a significant risk to go to the previous behavior before __GFP_THISNODE was added, it worked like that for years. This was simply an optimization to some lucky workloads that can fit in a single node, but it ended up breaking the VM for others that can't possibly fit in a single node, so going back is safe. Thanks, Andrea
