From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 25 Jan 2007 15:00:21 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [RFC] Limit the size of the pagecache Message-Id: <20070125150021.bf600997.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <45B842E6.5040008@redhat.com> 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> <45B842E6.5040008@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Rik van Riel 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: On Thu, 25 Jan 2007 00:40:54 -0500 Rik van Riel wrote: > KAMEZAWA Hiroyuki wrote: > > On Wed, 24 Jan 2007 23:28:15 -0500 > > Rik van Riel wrote: > > > >> KAMEZAWA Hiroyuki wrote: > > 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. > I agree. My current concerns is not adding knobs but how to show/explain what the users does. In most case, users don't know what they does and believes system-information can tell that. for example) A user sometimes asks "why amount of system-A's pagecache and system-B's are different from each other ?. I definitly does the same jobs on the both system." ...just because he used different deta-set ;) Thanks, -Kame -- 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