From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f200.google.com (mail-wr0-f200.google.com [209.85.128.200]) by kanga.kvack.org (Postfix) with ESMTP id 6BAFD6B0069 for ; Tue, 26 Sep 2017 09:33:23 -0400 (EDT) Received: by mail-wr0-f200.google.com with SMTP id v109so12631321wrc.5 for ; Tue, 26 Sep 2017 06:33:23 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id m188si1708519wme.135.2017.09.26.06.33.21 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 26 Sep 2017 06:33:21 -0700 (PDT) Date: Tue, 26 Sep 2017 15:33:20 +0200 From: Jan Kara Subject: Re: [PATCH v3] mm: introduce validity check on vm dirtiness settings Message-ID: <20170926133320.GD13627@quack2.suse.cz> References: <1505861015-11919-1-git-send-email-laoar.shao@gmail.com> <20170926102532.culqxb45xwzafomj@dhcp22.suse.cz> <20170926112656.tbu7nr2lxdqt5rft@dhcp22.suse.cz> <20170926115423.wdnctuqtxbhpdidx@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170926115423.wdnctuqtxbhpdidx@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Yafang Shao , Jan Kara , akpm@linux-foundation.org, Johannes Weiner , vdavydov.dev@gmail.com, jlayton@redhat.com, nborisov@suse.com, Theodore Ts'o , mawilcox@microsoft.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Tue 26-09-17 13:54:23, Michal Hocko wrote: > On Tue 26-09-17 19:45:45, Yafang Shao wrote: > > >> > To be honest I am not entirely sure this is worth the code and the > > >> > future maintenance burden. > > >> I'm not sure if this code is a burden for the future maintenance, but > > >> I think that if we don't introduce this code it is a burden to the > > >> admins. > > > > > > anytime we might need to tweak background vs direct limit we would have > > > to change these checks as well and that sounds like a maint. burden to > > > me. > > > > Would pls. show me some example ? > > What kind of examples would you like to see. I meant that if the current > logic of bacground vs. direct limit changes the code to check it which > is at a different place IIRC would have to be kept in sync. > > That being said, this is my personal opinion, I will not object if there > is a general consensus on merging this. I just believe that this is not > simply worth adding a single line of code. You can then a lot of harm by > setting different values which would pass the added check. So I personally think that the checks Yafang added are worth the extra code. The situation with ratio/bytes interface and hard/background limit is complex enough that it makes sense to have basic sanity checks to me. That being said I don't have too strong opinion on this so just documentation update would be also fine by me. Honza -- Jan Kara SUSE Labs, CR -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org