From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io1-f70.google.com (mail-io1-f70.google.com [209.85.166.70]) by kanga.kvack.org (Postfix) with ESMTP id A1B8F6B0008 for ; Mon, 15 Oct 2018 06:58:12 -0400 (EDT) Received: by mail-io1-f70.google.com with SMTP id f5-v6so17858768ioq.17 for ; Mon, 15 Oct 2018 03:58:12 -0700 (PDT) Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [202.181.97.72]) by mx.google.com with ESMTPS id f123-v6si8390047itd.9.2018.10.15.03.58.10 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 15 Oct 2018 03:58:11 -0700 (PDT) Subject: Re: [RFC PATCH] memcg, oom: throttle dump_header for memcg ooms without eligible tasks References: <000000000000dc48d40577d4a587@google.com> <20181010151135.25766-1-mhocko@kernel.org> <20181012112008.GA27955@cmpxchg.org> <20181012120858.GX5873@dhcp22.suse.cz> <9174f087-3f6f-f0ed-6009-509d4436a47a@i-love.sakura.ne.jp> <20181012124137.GA29330@cmpxchg.org> <0417c888-d74e-b6ae-a8f0-234cbde03d38@i-love.sakura.ne.jp> <20181013112238.GA762@cmpxchg.org> <20181015081934.GD18839@dhcp22.suse.cz> From: Tetsuo Handa Message-ID: Date: Mon, 15 Oct 2018 19:57:35 +0900 MIME-Version: 1.0 In-Reply-To: <20181015081934.GD18839@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: 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 , Sergey Senozhatsky , Petr Mladek , Sergey Senozhatsky , Steven Rostedt On 2018/10/15 17:19, Michal Hocko wrote: > As so many dozens of times before, I will point you to an incremental > nature of changes we really prefer in the mm land. We are also after a > simplicity which your proposal lacks in many aspects. You seem to ignore > that general approach and I have hard time to consider your NAK as a > relevant feedback. Going to an extreme and basing a complex solution on > it is not going to fly. No killable process should be a rare event which > requires a seriously misconfigured memcg to happen so wildly. If you can > trigger it with a normal user privileges then it would be a clear bug to > address rather than work around with printk throttling. > I can trigger 200+ times / 900+ lines / 69KB+ of needless OOM messages with a normal user privileges. This is a lot of needless noise/delay. No killable process is not a rare event, even without root privileges. [root@ccsecurity kumaneko]# time ./a.out Killed real 0m2.396s user 0m0.000s sys 0m2.970s [root@ccsecurity ~]# dmesg | grep 'no killable' | wc -l 202 [root@ccsecurity ~]# dmesg | wc 942 7335 70716 [root@ccsecurity ~]# ---------------------------------------- #define _GNU_SOURCE #include #include #include #include #include #include #include #include #define NUMTHREADS 256 #define MMAPSIZE 4 * 10485760 #define STACKSIZE 4096 static int pipe_fd[2] = { EOF, EOF }; static int memory_eater(void *unused) { int fd = open("/dev/zero", O_RDONLY); char *buf = mmap(NULL, MMAPSIZE, PROT_WRITE | PROT_READ, MAP_ANONYMOUS | MAP_SHARED, EOF, 0); read(pipe_fd[0], buf, 1); read(fd, buf, MMAPSIZE); pause(); return 0; } int main(int argc, char *argv[]) { int i; char *stack; FILE *fp; const unsigned long size = 1048576 * 200; mkdir("/sys/fs/cgroup/memory/test1", 0755); fp = fopen("/sys/fs/cgroup/memory/test1/memory.limit_in_bytes", "w"); fprintf(fp, "%lu\n", size); fclose(fp); fp = fopen("/sys/fs/cgroup/memory/test1/tasks", "w"); fprintf(fp, "%u\n", getpid()); fclose(fp); if (setgid(-2) || setuid(-2)) return 1; stack = mmap(NULL, STACKSIZE * NUMTHREADS, PROT_WRITE | PROT_READ, MAP_ANONYMOUS | MAP_SHARED, EOF, 0); for (i = 0; i < NUMTHREADS; i++) if (clone(memory_eater, stack + (i + 1) * STACKSIZE, CLONE_SIGHAND | CLONE_THREAD | CLONE_VM | CLONE_FS | CLONE_FILES, NULL) == -1) break; sleep(1); close(pipe_fd[1]); pause(); return 0; } ----------------------------------------