Hi, In an effort to learn more about transparent huge pages and NUMA, I have written a very simple C snippet that malloc()s in a loop. I am running this under numactl with an interleave policy across both the NUMA nodes in the system. To make watching allocation progress easier, I am malloc()ing 4k (1 page) at a time. If I watch node usage for the process (numa_maps) allocation looks correct (interleave), but then allocation will drop on one node and increase on another, at the same time as I see an increase in pages_collapsed. It appears as though pages are always migrating away from and to the same nodes, resulting in allocation (again, by examining numa_maps) being almost entirely on one node. This leads me to believe that khugepaged's defrag is to blame, though I am not certain. I tried to disable transparent huge page defrag completely via the following under /sys: /sys/kernel/mm/transparent_hugepage/defrag /sys/kernel/mm/transparent_hugepage/khugepaged/defrag but the same behavior persists. I am not sure if this is an indication that I don't know how to control transparent huge page collapse, or or that my issue isn't defrag/collapse related. Do I understand what I am seeing? Does anyone have any thoughts on this? The OS is CentOS5.8 running the Oracle Unbreakable Kernel 2, 2.6.39-400.109.4.el5uek. Further questions: The way I understand it, transparent_hugepage/defrag controls defrag on page fault, and transparent_hugepage/khugepaged/defrag controls maintenance defrag (time based). Is that correct? Thanks. Andy -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>