From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f197.google.com (mail-wr0-f197.google.com [209.85.128.197]) by kanga.kvack.org (Postfix) with ESMTP id 3DB4F6B0038 for ; Wed, 27 Sep 2017 15:33:34 -0400 (EDT) Received: by mail-wr0-f197.google.com with SMTP id z46so2902122wrz.2 for ; Wed, 27 Sep 2017 12:33:34 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id 3si18413wmt.155.2017.09.27.12.33.32 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 27 Sep 2017 12:33:32 -0700 (PDT) Date: Wed, 27 Sep 2017 12:33:30 -0700 From: Andrew Morton Subject: Re: [PATCH v4] mm: introduce validity check on vm dirtiness settings Message-Id: <20170927123330.90dadc97988326b3c594db00@linux-foundation.org> In-Reply-To: References: <1506035552-13010-1-git-send-email-laoar.shao@gmail.com> <20170926165949.77e27aea0b92a226e7905060@linux-foundation.org> <20170926195409.0867d13620e1219ca6676821@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Yafang Shao Cc: linux-mm@kvack.org On Wed, 27 Sep 2017 12:14:10 +0800 Yafang Shao wrote: > 2017-09-27 10:54 GMT+08:00 Andrew Morton : > > On Wed, 27 Sep 2017 09:38:21 +0800 Yafang Shao wrote: > > > >> > And existing scripts which do not do this will cease to work correctly, > >> > no? > >> > > >> > >> The existing scritpts won't work correctly. That's also what I have > >> worried before. > >> > >> But under this condition, there's a error message generated by "sysctl > >> -w" to tell them the first setting was failure. > >> This error message may be a reminder to them that there are some > >> connections between background and direct limit, and should not set > >> arbitrary. > >> May that's better. I'm not sure. > > > > Maybe we can leave the logic as-is and simply print a warning when an > > illogical state exists. > > > > You mean, just modified the code as bellow ? > in function domain_dirty_limits() > - if (bg_thresh >= thresh) > + if (bg_thresh >= thresh) { > + pr_warn("vm direct limit should greater than background limit.\n"); > bg_thresh = thresh / 2; > + } Something like that. > will this generate lots of log ? Well, it's one message per write to a procfs file, when that write causes an errant state. Sounds manageable? It would be nice if we could somehow help the operator to figure out that writing in a different order will prevent the incorrect state (and hence the warning). -- 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