From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2531EC4338F for ; Tue, 27 Jul 2021 08:06:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 04ECF611F2 for ; Tue, 27 Jul 2021 08:06:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235909AbhG0IF6 (ORCPT ); Tue, 27 Jul 2021 04:05:58 -0400 Received: from relay.sw.ru ([185.231.240.75]:55596 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235679AbhG0ICu (ORCPT ); Tue, 27 Jul 2021 04:02:50 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=virtuozzo.com; s=relay; h=Content-Type:MIME-Version:Date:Message-ID:From: Subject; bh=W5ZkylOW4aorWqYoZgdy9OUAHDEpy8dU4QmNRvPVlOs=; b=Yj12nar4kB+x0tcn9 97g0z8UReUWtZBd8M7TK4t+EblgWkMtLRxzEGpJndlo5lJBaTOwX6Ie72E40Rk0K8jA0cK/uuB36K LvHZgC3Qjsg3GnIS9NTYCQTgU7QuHIYd0xtpICYl/ho2irAdnFnf2UYH2M9kP6NIg+CLeRnurfSpY =; Received: from [10.93.0.56] by relay.sw.ru with esmtp (Exim 4.94.2) (envelope-from ) id 1m8I2q-005M9I-NF; Tue, 27 Jul 2021 11:02:32 +0300 Subject: Re: [PATCH v7 09/10] memcg: enable accounting for tty-related objects To: Jiri Slaby Cc: cgroups@vger.kernel.org, Greg Kroah-Hartman , linux-kernel@vger.kernel.org References: <6f21a0e0-bd36-b6be-1ffa-0dc86c06c470@virtuozzo.com> <1eef95fe-6172-796e-edd1-095545da6e74@kernel.org> From: Vasily Averin Message-ID: Date: Tue, 27 Jul 2021 11:02:31 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <1eef95fe-6172-796e-edd1-095545da6e74@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/27/21 9:54 AM, Jiri Slaby wrote: > 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? No, you are right, I've missed this. Typical terminals inside containers use TTY_DRIVER_RESET_TERMIOS flag and therefore do not save termios. So its accounting have near-to-zero impact in real life. I'll prepare fixup to drop GFP_KERNEL_ACCOUNT here. Thank you very much, Vasily Averin >>           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,