From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by kanga.kvack.org (Postfix) with ESMTP id C16D86B0008 for ; Thu, 18 Oct 2018 07:24:01 -0400 (EDT) Received: by mail-ed1-f72.google.com with SMTP id m45-v6so18441269edc.2 for ; Thu, 18 Oct 2018 04:24:01 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id x16-v6si4347239ejc.242.2018.10.18.04.24.00 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Oct 2018 04:24:00 -0700 (PDT) Date: Thu, 18 Oct 2018 13:23:58 +0200 From: Michal Hocko Subject: Re: [PATCH v3] mm: memcontrol: Don't flood OOM messages with no eligible task. Message-ID: <20181018112358.GB18839@dhcp22.suse.cz> References: <20181017102821.GM18839@dhcp22.suse.cz> <20181017111724.GA459@jagdpanzerIV> <201810180246.w9I2koi3011358@www262.sakura.ne.jp> <20181018065519.GV18839@dhcp22.suse.cz> <6bbb0449-1f22-4d05-9e2a-636965b7dbc6@i-love.sakura.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6bbb0449-1f22-4d05-9e2a-636965b7dbc6@i-love.sakura.ne.jp> Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa Cc: Sergey Senozhatsky , Johannes Weiner , linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, guro@fb.com, kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org, rientjes@google.com, yang.s@alibaba-inc.com, Andrew Morton , Petr Mladek , Sergey Senozhatsky , Steven Rostedt , syzbot On Thu 18-10-18 19:37:18, Tetsuo Handa wrote: > On 2018/10/18 15:55, Michal Hocko wrote: > > On Thu 18-10-18 11:46:50, Tetsuo Handa wrote: > >> This is essentially a ratelimit approach, roughly equivalent with: > >> > >> static DEFINE_RATELIMIT_STATE(oom_no_victim_rs, 60 * HZ, 1); > >> oom_no_victim_rs.flags |= RATELIMIT_MSG_ON_RELEASE; > >> > >> if (__ratelimit(&oom_no_victim_rs)) { > >> dump_header(oc, NULL); > >> pr_warn("Out of memory and no killable processes...\n"); > >> oom_no_victim_rs.begin = jiffies; > >> } > > > > Then there is no reason to reinvent the wheel. So use the standard > > ratelimit approach. Or put it in other words, this place is no special > > to any other that needs some sort of printk throttling. We surely do not > > want an ad-hoc solutions all over the kernel. > > netdev_wait_allrefs() in net/core/dev.c is doing the same thing. Since > out_of_memory() is serialized by oom_lock mutex, there is no need to use > "struct ratelimit_state"->lock field. Plain "unsigned long" is enough. That code probably predates generalized ratelimit api. > > And once you realize that the ratelimit api is the proper one (put aside > > any potential improvements in the implementation of this api) then you > > quickly learn that we already do throttle oom reports and it would be > > nice to unify that and ... we are back to a naked patch. So please stop > > being stuborn and try to cooperate finally. > > I don't think that ratelimit API is the proper one, for I am touching > "struct ratelimit_state"->begin field which is not exported by ratelimit API. > But if you insist on ratelimit API version, I can tolerate with below one. I just give up. I do not really see why you always have to make the code more complex than necessary and squash different things together. This is a complete kernel code development antipattern. I am not goging to reply to this thread more but let me note that this is beyond fun in any aspect I can think off (and yeah I have considered dark sense of humor as well). > > mm/oom_kill.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index f10aa53..7c6118e 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -1106,6 +1106,12 @@ bool out_of_memory(struct oom_control *oc) > select_bad_process(oc); > /* Found nothing?!?! */ > if (!oc->chosen) { > + static DEFINE_RATELIMIT_STATE(no_eligible_rs, 60 * HZ, 1); > + > + ratelimit_set_flags(&no_eligible_rs, RATELIMIT_MSG_ON_RELEASE); > + if ((is_sysrq_oom(oc) || is_memcg_oom(oc)) && > + !__ratelimit(&no_eligible_rs)) > + return false; > dump_header(oc, NULL); > pr_warn("Out of memory and no killable processes...\n"); > /* > @@ -1115,6 +1121,7 @@ bool out_of_memory(struct oom_control *oc) > */ > if (!is_sysrq_oom(oc) && !is_memcg_oom(oc)) > panic("System is deadlocked on memory\n"); > + no_eligible_rs.begin = jiffies; > } > if (oc->chosen && oc->chosen != (void *)-1UL) > oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" : > -- > 1.8.3.1 -- Michal Hocko SUSE Labs