From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jiri Slaby Subject: Re: [PATCH v7 09/10] memcg: enable accounting for tty-related objects Date: Tue, 27 Jul 2021 08:54:31 +0200 Message-ID: <1eef95fe-6172-796e-edd1-095545da6e74@kernel.org> References: <6f21a0e0-bd36-b6be-1ffa-0dc86c06c470@virtuozzo.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Vasily Averin , Andrew Morton Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Michal Hocko , Shakeel Butt , Johannes Weiner , Vladimir Davydov , Roman Gushchin , Greg Kroah-Hartman , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org On 27. 07. 21, 7:34, Vasily Averin wrote: > 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. > > Signed-off-by: Vasily Averin > Acked-by: Greg Kroah-Hartman > --- > drivers/tty/tty_io.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c > index 26debec..e787f6f 100644 > --- a/drivers/tty/tty_io.c > +++ b/drivers/tty/tty_io.c > @@ -1493,7 +1493,7 @@ void tty_save_termios(struct tty_struct *tty) > /* Stash the termios data */ > tp = tty->driver->termios[idx]; > if (tp == NULL) { > - tp = kmalloc(sizeof(*tp), GFP_KERNEL); > + tp = kmalloc(sizeof(*tp), GFP_KERNEL_ACCOUNT); termios are not saved for PTYs (TTY_DRIVER_RESET_TERMIOS). Am I missing something? > if (tp == NULL) > return; > tty->driver->termios[idx] = tp; > @@ -3119,7 +3119,7 @@ struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx) > { > struct tty_struct *tty; > > - tty = kzalloc(sizeof(*tty), GFP_KERNEL); > + tty = kzalloc(sizeof(*tty), GFP_KERNEL_ACCOUNT); > if (!tty) > return NULL; > > thanks, -- js suse labs