From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Hansen Subject: Re: Containers and /proc/sys/vm/drop_caches Date: Thu, 06 Jan 2011 13:50:05 -0800 Message-ID: <1294350605.26733.3.camel@nimitz> References: <20110105094022.GA5366@glandium.org> <4D243EC3.1050101@free.fr> <20110105140159.GC2718@hallyn.com> <20110106214315.GJ29064@count0.beaverton.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20110106214315.GJ29064-52DBMbEzqgQ/wnmkkaCWp/UQ3DHhIser@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Matt Helsley Cc: containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Mike Hommey , Balbir Singh List-Id: containers.vger.kernel.org On Thu, 2011-01-06 at 13:43 -0800, Matt Helsley wrote: > That said, the more important question is why should we provide > drop_caches inside a container? My understanding is it's largely a > workload-debugging tool and not something meant to truly solve > problems. If that's the case then we shouldn't provide it at all or it > should actually interfere with the host cache. Yeah, what's the problem that you're solving with drop_caches? The odds are, there's a better way. That said, it _might_ be worth doing things like dropping (inode or dentry) caches per-sb. That's a much better fit than using big, ugly, loosely-defined, system-wide knobs like drop_caches. Also, unless we start giving containers real ownership of devices or partitions, it's going to be pretty darn hard to let things clear caches in a meaningful way. What if one container wants an object cleared while another doesn't? -- Dave