In container mode, all temp directories are now on a tmpfs "RAM disk". This affects everything written to directories in the hidden or overlay modes. Files written there are now included in the memory measurements and the memory limit! The advantage is that performance should be more deterministic, especially if several runs use much I/O in parallel. This feature can be disabled with --no-tmpfs. /dev/shm and /run/shm are now available inside the container and provide a tmpfs instance (even with --no-tmpfs) as required by some tools for shared memory. Container mode now recommends LXCFS and automatically uses it if available for a better container isolation (e.g., uptime measures container uptime, not host uptime). On Debian/Ubuntu, just use sudo apt install lxcfs. Several small bug fixes and other improvements of isolation for container mode (e.g., host name in container is no longer the real host name). Add benchexec --no-hyperthreading, which restricts core assignments to a single virtual core per physical CPU core (all other sibling cores will stay unused). Thanks @alohamora!