From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from d28relay04.in.ibm.com (d28relay04.in.ibm.com [9.184.220.61]) by e28smtp02.in.ibm.com (8.13.1/8.13.1) with ESMTP id m4N6kDG9008983 for ; Fri, 23 May 2008 12:16:13 +0530 Received: from d28av05.in.ibm.com (d28av05.in.ibm.com [9.184.220.67]) by d28relay04.in.ibm.com (8.13.8/8.13.8/NCO v8.7) with ESMTP id m4N6k1jN1298436 for ; Fri, 23 May 2008 12:16:01 +0530 Received: from d28av05.in.ibm.com (loopback [127.0.0.1]) by d28av05.in.ibm.com (8.13.1/8.13.3) with ESMTP id m4N6kDnB021596 for ; Fri, 23 May 2008 12:16:13 +0530 Message-ID: <483667FB.1030702@linux.vnet.ibm.com> Date: Fri, 23 May 2008 12:15:15 +0530 From: Balbir Singh Reply-To: balbir@linux.vnet.ibm.com MIME-Version: 1.0 Subject: Re: [PATCH 0/4] swapcgroup(v2) References: <48364D38.7000304@linux.vnet.ibm.com> <4836563B.4060603@anu.edu.au> <20080523145947.84F4.KOSAKI.MOTOHIRO@jp.fujitsu.com> In-Reply-To: <20080523145947.84F4.KOSAKI.MOTOHIRO@jp.fujitsu.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: KOSAKI Motohiro Cc: David.Singleton@anu.edu.au, Rik van Riel , YAMAMOTO Takashi , Daisuke Nishimura , Linux MM , Linux Containers , Hugh Dickins , Pavel Emelyanov List-ID: KOSAKI Motohiro wrote: >>> Have you seen any real world example of this? >> At the unsophisticated end, there are lots of (Fortran) HPC applications >> with very large static array declarations but only "use" a small fraction >> of that. Those users know they only need a small fraction and are happy >> to volunteer small physical memory limits that we (admins/queuing >> systems) can apply. >> >> At the sophisticated end, the use of numerous large memory maps in >> parallel HPC applications to gain visibility into other processes is >> growing. We have processes with VSZ > 400GB just because they have >> 4GB maps into 127 other processes. Their physical page use is of >> the order 2GB. > > Ah, agreed. > Fujitsu HPC user said similar things ago. OK, so this use case is HPC specific. I am not against the swap controller, but overcommit can lead to problems if not controlled - such as OOM kill. The virtual address space limit helps applications fail gracefully rather than swap out excessively or OOM. I suspect there'll be applications that swing both ways. -- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL -- 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