From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 21 Aug 2008 19:59:15 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [discuss] memrlimit - potential applications that can use Message-Id: <20080821195915.f1ecd012.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <48AD42E1.40204@linux.vnet.ibm.com> References: <48AA73B5.7010302@linux.vnet.ibm.com> <1219161525.23641.125.camel@nimitz> <48AAF8C0.1010806@linux.vnet.ibm.com> <1219167669.23641.156.camel@nimitz> <48ABD545.8010209@linux.vnet.ibm.com> <1219249757.8960.22.camel@nimitz> <48ACE040.2030807@linux.vnet.ibm.com> <20080821164339.679212b2.kamezawa.hiroyu@jp.fujitsu.com> <48AD42E1.40204@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org Return-Path: To: balbir@linux.vnet.ibm.com Cc: Dave Hansen , Paul Menage , Dave Hansen , Andrea Righi , Hugh Dickins , Andrew Morton , Linux Memory Management List , linux kernel mailing list List-ID: On Thu, 21 Aug 2008 15:56:41 +0530 Balbir Singh wrote: > KAMEZAWA Hiroyuki wrote: > > On Thu, 21 Aug 2008 08:55:52 +0530 > > Balbir Singh wrote: > > > >>>>> So, before we expand the use of those features to control groups by > >>>>> adding a bunch of new code, let's make sure that there will be users > >>>> for > >>>>> it and that those users have no better way of doing it. > >>>> I am all ears to better ways of doing it. Are you suggesting that overcommit was > >>>> added even though we don't actually need it? > >>> It serves a purpose, certainly. We have have better ways of doing it > >>> now, though. "i>>?So, before we expand the use of those features to > >>> control groups by adding a bunch of new code, let's make sure that there > >>> will be users for it and that those users have no better way of doing > >>> it." > >>> > >>> The one concrete user that's been offered so far is postgres. I've > >> No, you've been offered several, including php and apache that use memory limits. > >> > >>> suggested something that I hope will be more effective than enforcing > >>> overcommit. > > > > I'm sorry I miss the point. My concern on memrlimit (for overcommiting) is that > > it's not fair because an application which get -ENOMEM at mmap() is just someone > > unlucky. > > It can happen today with overcommit turned on. Why is it unlucky? > Today's overcommit is also unlucky ;) For example) process A and B is under a memrlimit. process A no memory leak, it often calls malloc() and free(). process B does memory leak, 100MB per night. process A cannot do anything when it notices malloc() returns NULL. It controls his memory usage perfectly. He is unlucky and will die. process B can use up VSZ which is freed by process A. (OOM-killer, is disliked by everyone, have some kind of fairness. It checks usage.) > I think it's better to trigger some notifier to application or daemon > > rather than return -ENOMEM at mmap(). Notification like "Oh, it seems the VSZ > > of total application exceeds the limit you set. Although you can continue your > > operation, it's recommended that you should fix up the situation". > > will be good. > > > > So you are suggesting that when we are running out of memory (as defined by our > current resource constraints), we don't return -ENOMEM, but instead we now > handle a new event that states that we are running out of memory? > Not "running out of memory" Just "VSZ is over the limit you set/expected". My point is an application witch can handle NULL returned by malloc() is not very popular, I think. Sorry for noise. Thanks, -Kame > NOTE: I am not opposed to the event, it can be useful for container > administrators to know how to size their containers, not to application > developers who want to auto-tune their applications (see my comment on autonomic > computing in an earlier thread) or to applications that want to make sure they > don't OOM without the system administrator having to do oom_adj for every > important application. > -- 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