From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [patch 00/20] VM pageout scalability improvements From: Matt Mackall In-Reply-To: <20071223201149.7b88888f@bree.surriel.com> References: <20071218211539.250334036@redhat.com> <476D7334.4010301@linux.vnet.ibm.com> <20071222192119.030f32d5@bree.surriel.com> <476EE858.202@linux.vnet.ibm.com> <20071223201149.7b88888f@bree.surriel.com> Content-Type: text/plain Date: Thu, 27 Dec 2007 21:20:41 -0600 Message-Id: <1198812041.4406.63.camel@cinder.waste.org> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Rik van Riel Cc: balbir@linux.vnet.ibm.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, lee.schermerhorn@hp.com List-ID: On Sun, 2007-12-23 at 20:11 -0500, Rik van Riel wrote: > On Mon, 24 Dec 2007 04:29:36 +0530 > Balbir Singh wrote: > > Rik van Riel wrote: > > > > In the real world, users with large JVMs on their servers, which > > > sometimes go a little into swap, can trigger this system. All of > > > the CPUs end up scanning the active list, and all pages have the > > > referenced bit set. Even if the system eventually recovers, it > > > might as well have been dead. > > > > > > Going into swap a little should only take a little bit of time. > > > > Very fascinating, so we need to scale better with larger memory. > > I suspect part of the answer will lie with using large/huge pages. > > Linus vetoed going to a larger soft page size, with good reason. > > Just look at how much the 64kB page size on PPC64 sucks for most > workloads - it works for PPC64 because people buy PPC64 monster > systems for the kinds of monster workloads that work well with a > large page size, but it definately isn't general purpose. Indeed, machines already exist with >> 1TB of RAM, so even going to 1MB pages leaves these machines in trouble. Going to big pages a few years ago would have pushed the problem back a few years, but now we need real fixes. -- Mathematics is the supreme nostalgia of our time. -- 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