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=-16.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 DFF8AC432BE for ; Tue, 27 Jul 2021 09:31:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A268960F90 for ; Tue, 27 Jul 2021 09:31:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236107AbhG0JbB (ORCPT ); Tue, 27 Jul 2021 05:31:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:60972 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235946AbhG0JbA (ORCPT ); Tue, 27 Jul 2021 05:31:00 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 02CAB600D4; Tue, 27 Jul 2021 09:30:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1627378260; bh=gs7eJAOqHz0y0MgMzJHu3ENkS4NCcGHEBd0dG2aBni0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=v8yO2l0eRWB/MYAfEFD4kEBZ0ammK/F7vGp/bD8qlkWhbdzyXMf5OTl/WV6aCmwRr NjqHbDxoErEydeC8LzISazDpfl2UqCz38OFhI8qHtoyHWruTnfX7LCq06bvpwH0OCe 3FVEiM1doxBuTndQ+PNs0joLCTlKBAsCLyBhHks8= Date: Tue, 27 Jul 2021 11:30:58 +0200 From: Greg Kroah-Hartman To: Vasily Averin Cc: Jiri Slaby , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v7 09/10] memcg: enable accounting for tty-related objects Message-ID: References: <6f21a0e0-bd36-b6be-1ffa-0dc86c06c470@virtuozzo.com> <1eef95fe-6172-796e-edd1-095545da6e74@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 27, 2021 at 11:02:31AM +0300, Vasily Averin wrote: > 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. I'll go drop this patch from my tree. thanks, greg k-h