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=-11.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 61B8EC433ED for ; Wed, 28 Apr 2021 07:38:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2C4C7600D4 for ; Wed, 28 Apr 2021 07:38:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236666AbhD1HjA (ORCPT ); Wed, 28 Apr 2021 03:39:00 -0400 Received: from mail.kernel.org ([198.145.29.99]:45774 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230145AbhD1Hiv (ORCPT ); Wed, 28 Apr 2021 03:38:51 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7C462613F3; Wed, 28 Apr 2021 07:38:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1619595486; bh=QBnMC6nBzJ7jyPXp0bvf8FizKe3kkFoosH+sK00xjf8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=IelduBmo8Z3egwJsjYkZqs/jOFjlgurmn6LjPrBRBFKU7Vy3L97eMta9CDfcaSOlo NMPhseosskZD/a38E8FYsfJeUfx6Dm4LWJPHpKMaqR+EiLmz8XZiwMzdiPEp/rZ33T Phenb4Jn/pCUyjFzMOyuFbhe3YdTbxqBjMXfsJ2s= Date: Wed, 28 Apr 2021 09:38:03 +0200 From: Greg Kroah-Hartman To: Vasily Averin Cc: cgroups@vger.kernel.org, Michal Hocko , Shakeel Butt , Johannes Weiner , Vladimir Davydov , Roman Gushchin , Jiri Slaby , linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 15/16] memcg: enable accounting for tty-related objects Message-ID: References: <8664122a-99d3-7199-869a-781b21b7e712@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 28, 2021 at 09:54:16AM +0300, 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