From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 468A66B006A for ; Thu, 21 Jan 2010 19:40:20 -0500 (EST) Received: by pxi5 with SMTP id 5so430770pxi.12 for ; Thu, 21 Jan 2010 16:40:17 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20100122084856.600b2dd5.kamezawa.hiroyu@jp.fujitsu.com> References: <20100121145905.84a362bb.kamezawa.hiroyu@jp.fujitsu.com> <1264087124.1818.15.camel@barrios-desktop> <20100122084856.600b2dd5.kamezawa.hiroyu@jp.fujitsu.com> Date: Fri, 22 Jan 2010 09:40:17 +0900 Message-ID: <28c262361001211640w4ff6d61mdf682fa706ab61e@mail.gmail.com> Subject: Re: [PATCH] oom-kill: add lowmem usage aware oom kill handling From: Minchan Kim Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki Cc: "linux-mm@kvack.org" , "akpm@linux-foundation.org" , rientjes@google.com, "linux-kernel@vger.kernel.org" List-ID: On Fri, Jan 22, 2010 at 8:48 AM, KAMEZAWA Hiroyuki wrote: > On Fri, 22 Jan 2010 00:18:44 +0900 > Minchan Kim wrote: > >> Hi, Kame. >> >> On Thu, 2010-01-21 at 14:59 +0900, KAMEZAWA Hiroyuki wrote: >> > A patch for avoiding oom-serial-killer at lowmem shortage. >> > Patch is onto mmotm-2010/01/15 (depends on mm-count-lowmem-rss.patch) >> > Tested on x86-64/SMP + debug module(to allocated lowmem), works well. >> > >> > =3D=3D >> > From: KAMEZAWA Hiroyuki >> > >> > One cause of OOM-Killer is memory shortage in lower zones. >> > (If memory is enough, lowmem_reserve_ratio works well. but..) >> > >> > In lowmem-shortage oom-kill, oom-killer choses a vicitim process >> > on their vm size. But this kills a process which has lowmem memory >> > only if it's lucky. At last, there will be an oom-serial-killer. >> > >> > Now, we have per-mm lowmem usage counter. We can make use of it >> > to select a good? victim. >> > >> > This patch does >> > =C2=A0 - add CONSTRAINT_LOWMEM to oom's constraint type. >> > =C2=A0 - pass constraint to __badness() >> > =C2=A0 - change calculation based on constraint. If CONSTRAINT_LOWMEM, >> > =C2=A0 =C2=A0 use low_rss instead of vmsize. >> >> As far as low memory, it would be better to consider lowmem counter. >> But as you know, {vmsize VS rss} is debatable topic. >> Maybe someone doesn't like this idea. >> > About lowmem, vmsize never work well. > Tend to agree with you. I am just worried about "vmsize lovers". You removed considering vmsize totally. In case of LOWMEM, lowcount considering make sense. But never considering vmsize might be debatable. So personllay, I thouhg we could add more weight lowcount in case of LOWMEM. But I chaged my mind. I think it make OOM heurisic more complated without big benefit. Simple is best. >> So don't we need any test result at least? > My test result was very artificial, so I didn't attach the result. > > =C2=A0- Before this patch, sshd was killed at first. > =C2=A0- After this patch, memory consumer of low-rss was killed. Okay. You already anwsered my question by Balbir's reply. I had a question it's real problem and how often it happens. > >> If we don't have this patch, it happens several innocent process >> killing. but we can't prevent it by this patch. >> > I can't catch what you mean. I just said your patch's benefit. >> Sorry for bothering you. >> > > Hmm, boot option or CONFIG ? (CONFIG_OOMKILLER_EXTENSION ?) > > I'm now writing fork-bomb detector again and want to remove current > "gathering child's vm_size" heuristics. I'd like to put that under > the same config, too. Totally, I don't like CONFIG option for that. But vmsize lovers also don't want to change current behavior. So it's desirable until your fork-form detector become mature and prove it's good. One more questions about below. + if (constraint !=3D CONSTRAINT_LOWMEM) { + list_for_each_entry(child, &p->children, sibling) { + task_lock(child); + if (child->mm !=3D mm && child->mm) + points +=3D child->mm->total_vm/2 + 1; + task_unlock(child); + } Why didn't you consider child's lowmem counter in case of LOWMEM? > > Thanks, > -Kame > > > > > > > --=20 Kind regards, Minchan Kim -- 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