From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <45B842E6.5040008@redhat.com> Date: Thu, 25 Jan 2007 00:40:54 -0500 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [RFC] Limit the size of the pagecache References: <20070124121318.6874f003.kamezawa.hiroyu@jp.fujitsu.com> <20070124141510.7775829c.kamezawa.hiroyu@jp.fujitsu.com> <20070125093259.74f76144.kamezawa.hiroyu@jp.fujitsu.com> <20070125121254.a2e91875.kamezawa.hiroyu@jp.fujitsu.com> <45B831DF.7080506@redhat.com> <20070125141944.67347aeb.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20070125141944.67347aeb.kamezawa.hiroyu@jp.fujitsu.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: KAMEZAWA Hiroyuki Cc: clameter@sgi.com, aubreylee@gmail.com, svaidy@linux.vnet.ibm.com, nickpiggin@yahoo.com.au, rgetz@blackfin.uclinux.org, Michael.Hennerich@analog.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: KAMEZAWA Hiroyuki wrote: > On Wed, 24 Jan 2007 23:28:15 -0500 > Rik van Riel wrote: > >> KAMEZAWA Hiroyuki wrote: >> >>> FYI: >>> Because some customers are migrated from mainframes, they want to control >>> almost all features in OS, IOW, designing memory usages. >> Don't you mean: >> >> "Because some customers are migrating from mainframes, they are >> used to needing to control all features in OS" ? :) >> > Ah yes ;) > I always says Linux is different from mainframes. It's not just about Linux. Applications behave differently too from the way they were 15 years ago. Some databases, eg. sleepycat's db, map the whole database in memory. Other databases, like MySQL and postgresql, rely on the kernel's page cache to cache the most frequently accessed data. To make matters more interesting, memory sizes have increased by a factor 1000, but disk seek times have only gotten 10 times faster. This means that simplistic memory management algorithms can hurt performance a lot more than they could back then. In short, I am not convinced that any of the simple tunable knobs from the "good old days" will do much to actually help people with modern workloads on modern computers. -- Politics is the struggle between those who want to make their country the best in the world, and those who believe it already is. Each group calls the other unpatriotic. -- 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