From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx172.postini.com [74.125.245.172]) by kanga.kvack.org (Postfix) with SMTP id A27CC6B0078 for ; Thu, 1 Nov 2012 16:26:56 -0400 (EDT) Date: Thu, 1 Nov 2012 21:26:54 +0100 From: Pavel Machek Subject: Re: [PATCH] add some drop_caches documentation and info messsge Message-ID: <20121101202503.GA20817@xo-6d-61-c0.localdomain> References: <20121012125708.GJ10110@dhcp22.suse.cz> <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121024134836.a28d223a.akpm@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Dave Hansen , Michal Hocko , linux-mm@kvack.org, KAMEZAWA Hiroyuki , KOSAKI Motohiro , LKML Hi! > > > 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. :) > > Well who knows. Could be that people's vm *does* suck. Or they have > some particularly peculiar worklosd or requirement[*]. Or their VM > *used* to suck, and the drop_caches is not really needed any more but > it's there in vendor-provided code and they can't practically prevent > it. Or they have ipw wifi that does order 5 allocation :-). I seen drop_caches used in some android code, as part of SD card handling IIRC. > > 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? > > It was a rarely-used mainly-developer-only thing which, apparently, real > people found useful at some point in the past. Perhaps we should never > have offered it. And yes, documentation would be good. IIRC you claimed that drop_caches is not safe to use year-or-so-ago, is that still true? Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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