Messages in this thread | | | Date | Thu, 21 Aug 2008 19:59:15 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [discuss] memrlimit - potential applications that can use |
| |
On Thu, 21 Aug 2008 15:56:41 +0530 Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> KAMEZAWA Hiroyuki wrote: > > On Thu, 21 Aug 2008 08:55:52 +0530 > > Balbir Singh <balbir@linux.vnet.ibm.com> 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. "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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |