Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261467AbUKSQbZ (ORCPT ); Fri, 19 Nov 2004 11:31:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261443AbUKSQbZ (ORCPT ); Fri, 19 Nov 2004 11:31:25 -0500 Received: from 213-239-205-147.clients.your-server.de ([213.239.205.147]:27307 "EHLO debian.tglx.de") by vger.kernel.org with ESMTP id S261467AbUKSQ0C (ORCPT ); Fri, 19 Nov 2004 11:26:02 -0500 Subject: Re: [PATCH] fix spurious OOM kills From: Thomas Gleixner Reply-To: tglx@linutronix.de To: Marcelo Tosatti Cc: Andrew Morton , Martin MOKREJ__ , piggin@cyberone.com.au, chris@tebibyte.org, andrea@novell.com, LKML , linux-mm@kvack.org, Rik van Riel In-Reply-To: <20041119080946.GA30845@logos.cnet> References: <20041114202155.GB2764@logos.cnet> <419A2B3A.80702@tebibyte.org> <419B14F9.7080204@tebibyte.org> <20041117012346.5bfdf7bc.akpm@osdl.org> <419CD8C1.4030506@ribosome.natur.cuni.cz> <20041118131655.6782108e.akpm@osdl.org> <419D25B5.1060504@ribosome.natur.cuni.cz> <419D2987.8010305@cyberone.com.au> <419D383D.4000901@ribosome.natur.cuni.cz> <20041118160824.3bfc961c.akpm@osdl.org> <20041119080946.GA30845@logos.cnet> Content-Type: multipart/mixed; boundary="=-6BtNG+0wWdYTYeYfVJKf" Organization: linutronix Date: Fri, 19 Nov 2004 17:17:22 +0100 Message-Id: <1100881042.2635.140.camel@thomas> Mime-Version: 1.0 X-Mailer: Evolution 2.0.2 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6199 Lines: 247 --=-6BtNG+0wWdYTYeYfVJKf Content-Type: text/plain Content-Transfer-Encoding: 7bit On Fri, 2004-11-19 at 06:09 -0200, Marcelo Tosatti wrote: > As Thomas Gleixner has investigated, the OOM killer selection is problematic. > > When testing your ignore-page-referenced patch it first killed the memory hog > then shortly afterwards the shell I was running it on. > > You've seen Thomas emails, he has nice description there. I had another go on 2.6.10-rc2-mm2. The reentrancy blocking and the additional test of freepages in out_of_memory() make all the ugly time and counter checks superfluid. I think they were neccecary to make the spurious kill triggering less obvious. :) Can somebody else check with his test cases, if the behaviour is correct ? tglx --=-6BtNG+0wWdYTYeYfVJKf Content-Disposition: attachment; filename=2.6.10-rc2-mm2-oom.diff Content-Type: text/x-patch; name=2.6.10-rc2-mm2-oom.diff; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 7bit diff -urN 2.6.10-rc2-mm2.orig/mm/oom_kill.c 2.6.10-rc2-mm2/mm/oom_kill.c --- 2.6.10-rc2-mm2.orig/mm/oom_kill.c 2004-11-19 14:52:16.000000000 +0100 +++ 2.6.10-rc2-mm2/mm/oom_kill.c 2004-11-19 17:12:40.000000000 +0100 @@ -45,8 +45,10 @@ static unsigned long badness(struct task_struct *p, unsigned long uptime) { unsigned long points, cpu_time, run_time, s; + struct list_head *tsk; - if (!p->mm) + /* Ignore mm-less tasks and init */ + if (!p->mm || p->pid == 1) return 0; if (p->flags & PF_MEMDIE) @@ -57,6 +59,19 @@ points = p->mm->total_vm; /* + * Processes which fork a lot of child processes are likely + * a good choice. We add the vmsize of the childs if they + * have an own mm. This prevents forking servers to flood the + * machine with an endless amount of childs + */ + list_for_each(tsk, &p->children) { + struct task_struct *chld; + chld = list_entry(tsk, struct task_struct, sibling); + if (chld->mm != p->mm && chld->mm) + points += chld->mm->total_vm; + } + + /* * CPU time is in tens of seconds and run time is in thousands * of seconds. There is no particular reason for this other than * that it turned out to work very well in practice. @@ -176,6 +191,27 @@ return mm; } +static struct mm_struct *oom_kill_process(task_t *p) +{ + struct mm_struct *mm; + struct task_struct *g, *q; + + mm = oom_kill_task(p); + if (!mm) + return NULL; + /* + * kill all processes that share the ->mm (i.e. all threads), + * but are in a different thread group + */ + do_each_thread(g, q) + if (q->mm == mm && q->tgid != p->tgid) + __oom_kill_task(q); + + while_each_thread(g, q); + if (!p->mm) + printk(KERN_INFO "Fixed up OOM kill of mm-less task\n"); + return mm; +} /** * oom_kill - kill the "best" process when we run out of memory @@ -188,7 +224,9 @@ void oom_kill(void) { struct mm_struct *mm; - struct task_struct *g, *p, *q; + struct task_struct *c, *p; + struct list_head *tsk; + int mmcnt = 0; read_lock(&tasklist_lock); retry: @@ -200,21 +238,25 @@ panic("Out of memory and no killable processes...\n"); } - mm = oom_kill_task(p); - if (!mm) - goto retry; /* - * kill all processes that share the ->mm (i.e. all threads), - * but are in a different thread group + * Kill the child processes first */ - do_each_thread(g, q) - if (q->mm == mm && q->tgid != p->tgid) - __oom_kill_task(q); - while_each_thread(g, q); - if (!p->mm) - printk(KERN_INFO "Fixed up OOM kill of mm-less task\n"); + list_for_each(tsk, &p->children) { + c = list_entry(tsk, struct task_struct, sibling); + if (c->mm == p->mm) + continue; + mm = oom_kill_process(c); + if (mm) { + mmcnt ++; + mmput(mm); + } + } + mm = oom_kill_process(p); + if (!mmcnt && !mm) + goto retry; + if (mm) + mmput(mm); read_unlock(&tasklist_lock); - mmput(mm); return; } @@ -224,59 +266,23 @@ void out_of_memory(int gfp_mask) { /* - * oom_lock protects out_of_memory()'s static variables. - * It's a global lock; this is not performance-critical. - */ - static DEFINE_SPINLOCK(oom_lock); - static unsigned long first, last, count, lastkill; - unsigned long now, since; - - spin_lock(&oom_lock); - now = jiffies; - since = now - last; - last = now; - - /* - * If it's been a long time since last failure, - * we're not oom. - */ - if (since > 5*HZ) - goto reset; - - /* - * If we haven't tried for at least one second, - * we're not really oom. - */ - since = now - first; - if (since < HZ) - goto out_unlock; - - /* - * If we have gotten only a few failures, - * we're not really oom. - */ - if (++count < 10) - goto out_unlock; - - /* - * If we just killed a process, wait a while - * to give that task a chance to exit. This - * avoids killing multiple processes needlessly. - */ - since = now - lastkill; - if (since < HZ*5) - goto out_unlock; - - /* - * Ok, really out of memory. Kill something. - */ - lastkill = now; + * inprogress protects out_of_memory()'s static variables + * and prevents reentrancy + */ + static unsigned long inprogress; + static unsigned int freepages = 1000000; + + if (test_and_set_bit(0, &inprogress)) + return; + + /* Check, if memory was freed since the last oom kill */ + if (freepages < nr_free_pages()) + goto out_unlock; printk("oom-killer: gfp_mask=0x%x\n", gfp_mask); show_free_areas(); - - /* oom_kill() sleeps */ - spin_unlock(&oom_lock); + /* Store free pages * 2 for the check above */ + freepages = (nr_free_pages() << 1); oom_kill(); /* * Make kswapd go out of the way, so "p" has a good chance of @@ -284,17 +290,7 @@ * for more memory. */ yield(); - spin_lock(&oom_lock); - -reset: - /* - * We dropped the lock above, so check to be sure the variable - * first only ever increases to prevent false OOM's. - */ - if (time_after(now, first)) - first = now; - count = 0; - + out_unlock: - spin_unlock(&oom_lock); + clear_bit(0, &inprogress); } --=-6BtNG+0wWdYTYeYfVJKf-- - 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/