On Thu, 2025-07-31 at 20:41 +0200, Vlastimil Babka wrote: > On 7/31/25 20:34, Frank van der Linden wrote: > > Not sure what the right thing to do would be. Either explicitly boost > > the priority of a thread temporarily during migrate_pages_batch, or > > mitigate the issue by dealing with 'busy' pages more quickly in > > migrate_pages_batch. > > There's a workaround for realtime tasks. If you mlock[all]() their memory, > setting sysctl vm.compact_unevictable_allowed to 0 should exclude these > pages from migration by compaction. Hm, per documentation that's done automatically for PREEMPT_RT... On CONFIG_PREEMPT_RT the default value is 0 in order to avoid a page fault, due to compaction, which would block the task from becoming active until the fault is resolved. ...but rummaging, seems other stuff can step on it (contiguous alloc?). -Mike
