Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935121Ab2JYJYd (ORCPT ); Thu, 25 Oct 2012 05:24:33 -0400 Received: from mail.skyhub.de ([78.46.96.112]:58356 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934971Ab2JYJY3 (ORCPT ); Thu, 25 Oct 2012 05:24:29 -0400 Date: Thu, 25 Oct 2012 11:24:24 +0200 From: Borislav Petkov To: KOSAKI Motohiro Cc: Dave Hansen , Andrew Morton , Michal Hocko , linux-mm@kvack.org, KAMEZAWA Hiroyuki , LKML Subject: Re: [PATCH] add some drop_caches documentation and info messsge Message-ID: <20121025092424.GA16601@liondog.tnic> Mail-Followup-To: Borislav Petkov , KOSAKI Motohiro , Dave Hansen , Andrew Morton , Michal Hocko , linux-mm@kvack.org, KAMEZAWA Hiroyuki , LKML References: <20121023164546.747e90f6.akpm@linux-foundation.org> <20121024062938.GA6119@dhcp22.suse.cz> <20121024125439.c17a510e.akpm@linux-foundation.org> <50884F63.8030606@linux.vnet.ibm.com> <20121024134836.a28d223a.akpm@linux-foundation.org> <20121024210600.GA17037@liondog.tnic> <50885B2E.5050500@linux.vnet.ibm.com> <20121024224817.GB8828@liondog.tnic> <5088725B.2090700@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1465 Lines: 40 On Wed, Oct 24, 2012 at 08:56:45PM -0400, KOSAKI Motohiro wrote: > > That effectively means removing it from the kernel since distros ship > > with those config options off. We don't want to do that since there > > _are_ valid, occasional uses like benchmarking that we want to be > > consistent. > > Agreed. we don't want to remove valid interface never. Ok, duly noted. But let's discuss this a bit further. So, for the benchmarking aspect, you're either going to have to always require dmesg along with benchmarking results or /proc/vmstat, depending on where the drop_caches stats end up. Is this how you envision it? And then there are the VM bug cases, where you might not always get full dmesg from a panicked system. In that case, you'd want the kernel tainting thing too, so that it at least appears in the oops backtrace. Although the tainting thing might not be enough - a user could drop_caches at some point in time and the oops happening much later could be unrelated but that can't be expressed in taint flags. So you'd need some sort of a drop_caches counter, I'd guess. Or a last drop_caches timestamp something. Am I understanding the intent correctly? Thanks. -- Regards/Gruss, Boris. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/