From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757157AbaFYWQS (ORCPT ); Wed, 25 Jun 2014 18:16:18 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:43014 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755730AbaFYWQR (ORCPT ); Wed, 25 Jun 2014 18:16:17 -0400 Date: Thu, 26 Jun 2014 00:15:48 +0200 From: Pavel Machek To: Thomas Knauth Cc: dedekind1@gmail.com, David Rientjes , Maksym Planeta , Alexander Viro , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] sysctl: Add a feature to drop caches selectively Message-ID: <20140625221548.GA614@xo-6d-61-c0.localdomain> References: <1403626213-7691-1-git-send-email-mcsim.planeta@gmail.com> <1403677528.7903.103.camel@sauron.fi.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii 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 On Wed 2014-06-25 10:25:05, Thomas Knauth wrote: > On Wed, Jun 25, 2014 at 8:25 AM, Artem Bityutskiy wrote: > > Plus some explanations WRT why proc-based interface and what would be > > the alternatives, what if tomorrow we want to extend the functionality > > and drop caches only for certain file range, is this only for regular > > files or also for directories, why posix_fadvice(DONTNEED) is not > > sufficient. > > I suggested the idea originally. Let me address each of your questions in turn: > > Why a selective drop? To have a middle ground between echo 2 > > drop_caches and echo 3 > drop_caches. When is this interesting? My > particular use case was benchmarking. I wanted to repeatedly measure > the timing when things were read from disk. Dropping everything from > the cache, also drops useful things, not just the few files your > benchmark intends to measure. > > Why /proc? Because this is where the current drop_caches mechanism is > located. If it should go somewhere else, please do suggest so. It sounds like this should be a new syscall. echoing filenames in files is strange/ugly. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html