Wu Fengguang <fengguang.wu@xxxxxxxxx> writes: > Did you enable any NUMA policy? That could start swapping even if > there are lots of free pages in some nodes. Hi. Thanks for the follow-up. We haven't done any configuration or tuning of NUMA behaviour, but NUMA support is definitely compiled into the kernel: # zgrep NUMA /proc/config.gz CONFIG_NUMA_IRQ_DESC=y CONFIG_NUMA=y CONFIG_K8_NUMA=y CONFIG_X86_64_ACPI_NUMA=y # CONFIG_NUMA_EMU is not set CONFIG_ACPI_NUMA=y # grep -i numa /var/log/dmesg.boot NUMe: Allocated memnodemap from b000 - 1b540 NUMA: Using 20 for the hash shift. > Are your free pages equally distributed over the nodes? Or limited to > some of the nodes? Try this command: > > grep MemFree /sys/devices/system/node/node*/meminfo My worst-case machines current have swap completely turned off to make them usable for clients, but I have one machine which is about 3GB into swap with 8GB of buffers and 3GB free. This shows # grep MemFree /sys/devices/system/node/node*/meminfo /sys/devices/system/node/node0/meminfo:Node 0 MemFree: 954500 kB /sys/devices/system/node/node1/meminfo:Node 1 MemFree: 2374528 kB I could definitely imagine that one of the nodes could have dipped down to zero in the past. I'll try enabling swap on one of our machines with the bad problem late tonight and repeat the experiment. The node meminfo on this box currently looks like # grep MemFree /sys/devices/system/node/node*/meminfo /sys/devices/system/node/node0/meminfo:Node 0 MemFree: 82732 kB /sys/devices/system/node/node1/meminfo:Node 1 MemFree: 1723896 kB Best wishes, Chris. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>