From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752341Ab0IOGO2 (ORCPT ); Wed, 15 Sep 2010 02:14:28 -0400 Received: from e4.ny.us.ibm.com ([32.97.182.144]:60384 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751721Ab0IOGO1 (ORCPT ); Wed, 15 Sep 2010 02:14:27 -0400 Subject: Re: [RFC][PATCH] update /proc/sys/vm/drop_caches documentation From: Dave Hansen To: KOSAKI Motohiro Cc: KAMEZAWA Hiroyuki , linux-kernel@vger.kernel.org, linux-mm@kvack.org, lnxninja@linux.vnet.ibm.com In-Reply-To: <20100915135016.C9F1.A69D9226@jp.fujitsu.com> References: <20100914234714.8AF506EA@kernel.beaverton.ibm.com> <20100915133303.0b232671.kamezawa.hiroyu@jp.fujitsu.com> <20100915135016.C9F1.A69D9226@jp.fujitsu.com> Content-Type: text/plain; charset="ANSI_X3.4-1968" Date: Tue, 14 Sep 2010 23:14:22 -0700 Message-ID: <1284531262.27089.15725.camel@nimitz> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2010-09-15 at 13:53 +0900, KOSAKI Motohiro wrote: > > > ============================================================== > > > > > > diff -puN fs/drop_caches.c~update-drop_caches-documentation fs/drop_caches.c > > > --- linux-2.6.git/fs/drop_caches.c~update-drop_caches-documentation 2010-09-14 15:44:29.000000000 -0700 > > > +++ linux-2.6.git-dave/fs/drop_caches.c 2010-09-14 15:58:31.000000000 -0700 > > > @@ -47,6 +47,8 @@ int drop_caches_sysctl_handler(ctl_table > > > { > > > proc_dointvec_minmax(table, write, buffer, length, ppos); > > > if (write) { > > > + WARN_ONCE(1, "kernel caches forcefully dropped, " > > > + "see Documentation/sysctl/vm.txt\n"); > > > > Documentation updeta seems good but showing warning seems to be meddling to me. > > Agreed. > > If the motivation is blog's bogus rumor, this is no effective. I easily > imazine they will write "Hey, drop_caches may output strange message, > but please ignore it!". Fair enough. But, is there a point that we _should_ be warning? If someone is doing this every minute, or every hour, something is pretty broken. Should we at least be doing a WARN_ON() so that the TAINT_WARN is set? I'm worried that there are users out there experiencing real problems that aren't reporting it because "workarounds" like this just paper over the issue. -- Dave