[libvirt-users] Dealing with swappiness on host systems

Hi, I'm looking for a way to prevent qemu processes on a libvirt host to use swap unless there is no physical memory free but apparently this is not as easy as I'd hoped it would be. This is on a CentOS 7 system. At first I tried setting /proc/sys/vm/swappiness to 1 (apparently setting it to 0 now means even the OOM killer takes precedence over swapping: https://www.percona.com/blog/2014/04/28/oom-relation-vm-swappiness0-new-k... ). After doing this I could still see the used swap increase for a guest even though there were 28G of memory used only as page-cache on the host. Taking another look at it I notices that swappiness can now apparently be controlled on a per-process basis as well by means of using the files under /sys/fs/cgroup/memory/machine.slice however I found no good documentation describing which of the values takes precedence and whether these values can be modified on the fly the same way the files under /proc can. Has anyone pointers to documentation that explains how all of this works? More specifically: Which of these paths take precedence for a running process: /proc/sys/vm/swappiness /sys/fs/cgroup/memory/machine.slice/memory.swappiness /sys/fs/cgroup/memory/machine.slice/<guest-id>/memory.swappiness Can any/all of these values be modified on the fly and if not is there another way to tell qemu to prefer physical memory to swap and only use swap when no physical memory is available? Regards, Dennis