New RHEL6-based OpenVZ kernel has a new memory management model, which supersedes User beancounters. It is called VSwap.
Now you can set two primary parameters:
physpages and swappages, while all the other beancounters become secondary.- physpages
- This parameter limits the physical memory (RAM) available to processes inside a container.
- The
barrieris ignored, and thelimitsets the limit. - Currently the user memory and the page cache are accounted into
physpages.
- swappages
- This parameter limits the amount of swap space which can be used for processes inside a container.
- The
barrieris ignored, and thelimitsets the limit.
The sum of physpages.limit and swappages.limit limits the maximum amount of allocated memory which can be used by a container. When physpages limit is reached, memory pages belonging to the container are pushed out to so called virtual swap (vswap). The difference between normal swap and vswap is that with vswap no actual disk I/O usually occurs. Instead, a container is artificially slowed down, to emulate the effect of the real swapping. Actual swap out occurs only if there is a global memory shortage on the system.
