From: Vasily Averin <vvs@xxxxxxxxxxxxx> Subject: memcg: enable accounting for tty-related objects At each login the user forces the kernel to create a new terminal and allocate up to ~1Kb memory for the tty-related structures. By default it's allowed to create up to 4096 ptys with 1024 reserve for initial mount namespace only and the settings are controlled by host admin. Though this default is not enough for hosters with thousands of containers per node. Host admin can be forced to increase it up to NR_UNIX98_PTY_MAX = 1<<20. By default container is restricted by pty mount_opt.max = 1024, but admin inside container can change it via remount. As a result, one container can consume almost all allowed ptys and allocate up to 1Gb of unaccounted memory. It is not enough per-se to trigger OOM on host, however anyway, it allows to significantly exceed the assigned memcg limit and leads to troubles on the over-committed node. It makes sense to account for them to restrict the host's memory consumption from inside the memcg-limited container. Link: https://lkml.kernel.org/r/5d4bca06-7d4f-a905-e518-12981ebca1b3@xxxxxxxxxxxxx Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Shakeel Butt <shakeelb@xxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Jiri Slaby <jirislaby@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- drivers/tty/tty_io.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/tty/tty_io.c~memcg-enable-accounting-for-tty-related-objects +++ a/drivers/tty/tty_io.c @@ -3088,7 +3088,7 @@ struct tty_struct *alloc_tty_struct(stru { struct tty_struct *tty; - tty = kzalloc(sizeof(*tty), GFP_KERNEL); + tty = kzalloc(sizeof(*tty), GFP_KERNEL_ACCOUNT); if (!tty) return NULL; _
