From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758725Ab2JXU2j (ORCPT ); Wed, 24 Oct 2012 16:28:39 -0400 Received: from e34.co.us.ibm.com ([32.97.110.152]:60927 "EHLO e34.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755477Ab2JXU2h (ORCPT ); Wed, 24 Oct 2012 16:28:37 -0400 Message-ID: <50884F63.8030606@linux.vnet.ibm.com> Date: Wed, 24 Oct 2012 13:28:19 -0700 From: Dave Hansen User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120912 Thunderbird/15.0.1 MIME-Version: 1.0 To: Andrew Morton CC: Michal Hocko , linux-mm@kvack.org, KAMEZAWA Hiroyuki , KOSAKI Motohiro , LKML Subject: Re: [PATCH] add some drop_caches documentation and info messsge References: <20121012125708.GJ10110@dhcp22.suse.cz> <20121023164546.747e90f6.akpm@linux-foundation.org> <20121024062938.GA6119@dhcp22.suse.cz> <20121024125439.c17a510e.akpm@linux-foundation.org> In-Reply-To: <20121024125439.c17a510e.akpm@linux-foundation.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12102420-2876-0000-0000-00000154F125 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/24/2012 12:54 PM, Andrew Morton wrote: > hmpf. This patch worries me. If there are people out there who are > regularly using drop_caches because the VM sucks, it seems pretty > obnoxious of us to go dumping stuff into their syslog. What are they > supposed to do? Stop using drop_caches? People use drop_caches because they _think_ the VM sucks, or they _think_ they're "tuning" their system. _They_ are supposed to stop using drop_caches. :) What kind of interface _is_ it in the first place? Is it really a production-level thing that we expect users to be poking at? Or, is it a rarely-used debugging and benchmarking knob which is fair game for us to tweak like this? Do we have any valid uses of drop_caches where the printk() would truly _be_ disruptive? Are those cases where we _also_ have real kernel bugs or issues that we should be working? If it disrupts them and they go to their vendor or the community directly, it gives us at least a shot at fixing the real problems (or fixing the "invalid" use). Adding taint, making this a single-shot printk, or adding vmstat counters are all good ideas. I guess I think the disruption is a feature because I hope it will draw some folks out of the woodwork.