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4:09 AM, David Hildenbrand (Arm) wrote: >>> It was also found that adding '--mremap-numa' changes the behavior >>> substantially: >> "assign memory mapped pages to randomly selected NUMA nodes. This is >> disabled for systems that do not support NUMA." >> >> so this is just sharding your lock contention across your NUMA nodes (you >> have an lruvec per node). >> >>> stress-ng --mremap 8192 --mremap-bytes 4K --timeout 30 --mremap-numa >>> --metrics-brief >>> >>> mremap 2570798 29.39 8.06 106.23 87466.50 22494.74 >>> >>> So it's possible that either actual swapping, or the mbind(..., >>> MPOL_MF_MOVE) path used by '--mremap-numa', removes most of the excessive >>> system time. >>> >>> Does this look like a known MM scalability issue around short-lived >>> MAP_POPULATE / munmap churn? >> Yes. Is this an actual issue on some workload? > Same thought, it's unclear to me why we should care here. In particular, > when talking about excessive use of zero-filled pages. > Currently this is only showing up with that particular stress test. We will try John's patch and provide feedback. Thanks for all the feedback, everyone!