Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752829AbbLRMKb (ORCPT ); Fri, 18 Dec 2015 07:10:31 -0500 Received: from www262.sakura.ne.jp ([202.181.97.72]:52037 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752373AbbLRMKa (ORCPT ); Fri, 18 Dec 2015 07:10:30 -0500 To: mhocko@kernel.org, akpm@linux-foundation.org Cc: mgorman@suse.de, rientjes@google.com, torvalds@linux-foundation.org, oleg@redhat.com, hughd@google.com, andrea@kernel.org, riel@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] mm, oom: introduce oom reaper From: Tetsuo Handa References: <1450204575-13052-1-git-send-email-mhocko@kernel.org> <20151216165035.38a4d9b84600d6348a3cf4bf@linux-foundation.org> <20151217130223.GE18625@dhcp22.suse.cz> In-Reply-To: <20151217130223.GE18625@dhcp22.suse.cz> Message-Id: <201512182110.FBH73485.LFOFtOOVSHFQMJ@I-love.SAKURA.ne.jp> X-Mailer: Winbiff [Version 2.51 PL2] X-Accept-Language: ja,en,zh Date: Fri, 18 Dec 2015 21:10:26 +0900 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5896 Lines: 170 Michal Hocko wrote: > On Wed 16-12-15 16:50:35, Andrew Morton wrote: > > On Tue, 15 Dec 2015 19:36:15 +0100 Michal Hocko wrote: > [...] > > > +static void oom_reap_vmas(struct mm_struct *mm) > > > +{ > > > + int attempts = 0; > > > + > > > + while (attempts++ < 10 && !__oom_reap_vmas(mm)) > > > + schedule_timeout(HZ/10); > > > > schedule_timeout() in state TASK_RUNNING doesn't do anything. Use > > msleep() or msleep_interruptible(). I can't decide which is more > > appropriate - it only affects the load average display. > > Ups. You are right. I will go with msleep_interruptible(100). > I didn't know that. My testing was almost without oom_reap_vmas(). > > I guess it means that the __oom_reap_vmas() success rate is nice anud > > high ;) > > I had a debugging trace_printks around this and there were no reties > during my testing so I was probably lucky to not trigger the mmap_sem > contention. Yes, you are lucky that you did not hit the mmap_sem contention. I retested with static void oom_reap_vmas(struct mm_struct *mm) { int attempts = 0; while (attempts++ < 10 && !__oom_reap_vmas(mm)) - schedule_timeout(HZ/10); + msleep_interruptible(100); + printk(KERN_WARNING "oom_reaper: attempts=%u\n", attempts); /* Drop a reference taken by wake_oom_reaper */ mmdrop(mm); } and I can hit that attempts becomes 11 (i.e. oom_reap_vmas() gives up waiting) if I ran a memory stressing program with many contending mmap_sem readers and writers shown below. ---------- #define _GNU_SOURCE #include #include #include #include #include #include #include #include static cpu_set_t set = { { 1 } }; /* Allow only CPU 0. */ static char filename[32] = { }; /* down_read(&mm->mmap_sem) requester. */ static int reader(void *unused) { const int fd = open(filename, O_RDONLY); char buffer[128]; sched_setaffinity(0, sizeof(set), &set); sleep(2); while (pread(fd, buffer, sizeof(buffer), 0) > 0); while (1) pause(); return 0; } /* down_write(&mm->mmap_sem) requester. */ static int writer(void *unused) { const int fd = open("/proc/self/exe", O_RDONLY); sched_setaffinity(0, sizeof(set), &set); sleep(2); while (1) { void *ptr = mmap(NULL, 4096, PROT_READ, MAP_PRIVATE, fd, 0); munmap(ptr, 4096); } return 0; } static void my_clone(int (*func) (void *)) { char *stack = malloc(4096); if (stack) clone(func, stack + 4096, CLONE_THREAD | CLONE_SIGHAND | CLONE_VM, NULL); } /* Memory consumer for invoking the OOM killer. */ static void memory_eater(void) { char *buf = NULL; unsigned long i; unsigned long size = 0; sleep(4); for (size = 1048576; size < 512UL * (1 << 30); size <<= 1) { char *cp = realloc(buf, size); if (!cp) { size >>= 1; break; } buf = cp; } fprintf(stderr, "Start eating memory\n"); for (i = 0; i < size; i += 4096) buf[i] = '\0'; /* Will cause OOM due to overcommit */ } int main(int argc, char *argv[]) { int i; const pid_t pid = fork(); if (pid == 0) { for (i = 0; i < 9; i++) my_clone(writer); writer(NULL); _exit(0); } else if (pid > 0) { snprintf(filename, sizeof(filename), "/proc/%u/stat", pid); for (i = 0; i < 1000; i++) my_clone(reader); } memory_eater(); return *(char *) NULL; /* Not reached. */ } ---------- Complete log is at http://I-love.SAKURA.ne.jp/tmp/serial-20151218.txt.xz . ---------- [ 90.790847] Killed process 9560 (oom_reaper-test) total-vm:4312kB, anon-rss:124kB, file-rss:0kB, shmem-rss:0kB [ 91.803154] oom_reaper: attempts=11 [ 100.701494] MemAlloc-Info: 509 stalling task, 0 dying task, 1 victim task. [ 102.439082] Killed process 9559 (oom_reaper-test) total-vm:2170960kB, anon-rss:1564600kB, file-rss:0kB, shmem-rss:0kB [ 102.441937] Killed process 9561 (oom_reaper-test) total-vm:2170960kB, anon-rss:1564776kB, file-rss:0kB, shmem-rss:0kB [ 102.731326] oom_reaper: attempts=1 [ 125.420727] Killed process 10573 (oom_reaper-test) total-vm:4340kB, anon-rss:80kB, file-rss:0kB, shmem-rss:0kB [ 126.440392] oom_reaper: attempts=11 [ 135.354193] MemAlloc-Info: 450 stalling task, 0 dying task, 0 victim task. [ 240.023256] MemAlloc-Info: 1016 stalling task, 0 dying task, 0 victim task. [ 302.246975] Killed process 10572 (oom_reaper-test) total-vm:2170960kB, anon-rss:1562128kB, file-rss:0kB, shmem-rss:0kB [ 302.263515] oom_reaper: attempts=1 [ 382.961343] Killed process 11667 (oom_reaper-test) total-vm:4312kB, anon-rss:84kB, file-rss:0kB, shmem-rss:0kB [ 383.980541] oom_reaper: attempts=11 [ 392.592658] MemAlloc-Info: 758 stalling task, 10 dying task, 1 victim task. [ 399.497478] Killed process 11666 (oom_reaper-test) total-vm:2170960kB, anon-rss:1556072kB, file-rss:0kB, shmem-rss:0kB [ 399.499101] Killed process 11668 (oom_reaper-test) total-vm:2170960kB, anon-rss:1556260kB, file-rss:0kB, shmem-rss:0kB [ 399.778283] oom_reaper: attempts=1 [ 438.304082] Killed process 12680 (oom_reaper-test) total-vm:4324kB, anon-rss:120kB, file-rss:0kB, shmem-rss:0kB [ 439.318951] oom_reaper: attempts=11 [ 445.581171] MemAlloc-Info: 796 stalling task, 0 dying task, 0 victim task. [ 618.955215] MemAlloc-Info: 979 stalling task, 0 dying task, 0 victim task. ---------- Yes, this is an insane program. But what is important will be we prepare for cases when oom_reap_vmas() gave up waiting. Silent hang up is annoying. Like Andrew said ( http://lkml.kernel.org/r/20151216153513.e432dc70e035e5d07984710c@linux-foundation.org ), I want to add a watchdog for printk()ing. ( http://lkml.kernel.org/r/201512170011.IAC73451.FLtFMSJHOQFVOO@I-love.SAKURA.ne.jp ). -- 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/