linux-kernel - Re: Misleading OOM messages

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Date:	Fri, 22 May 2009 15:01:23 -0400 (EDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Pavel Machek <pavel@....cz>
cc:	Dave Hansen <dave@...ux.vnet.ibm.com>,
	David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Nick Piggin <npiggin@...e.de>, Mel Gorman <mel@....ul.ie>,
	Peter Ziljstra <a.p.ziljstra@...llo.nl>,
	San Mehat <san@...roid.com>, Arve Hj?nnev?g <arve@...roid.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Misleading OOM messages

Subject: Remove misleading kernel log entries about "Out of Memory" conditions

What we traditionally call an "out of memory" failure is mostly not really
related to having enough physical memory. "out of memory" occurs when the
memory reclaim attempts fail to provide enough memory for an allocation.

Typically there is a misconfiguration or kernel bug that is at the root
of an out of memory issue. The message suggests that the machine does
not have enough memory which is not true.

People have done strange things as a result of these messages. Some
put more physical memory into their machines others limit the memory
use of their applications with ulimit. Having a clear message avoids
these reactions.

So change the messages to describe what actually went wrong.

Signed-off-by: Christoph Lameter <cl@...ux-foundation.org>

---
 mm/oom_kill.c |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

Index: linux-2.6/mm/oom_kill.c
===================================================================
--- linux-2.6.orig/mm/oom_kill.c	2009-05-12 12:37:52.000000000 -0500
+++ linux-2.6/mm/oom_kill.c	2009-05-12 12:44:36.000000000 -0500
@@ -387,7 +387,7 @@ static int oom_kill_process(struct task_
 	struct task_struct *c;

 	if (printk_ratelimit()) {
-		printk(KERN_WARNING "%s invoked oom-killer: "
+		printk(KERN_WARNING "%s invoked process-killer: "
 			"gfp_mask=0x%x, order=%d, oomkilladj=%d\n",
 			current->comm, gfp_mask, order, current->oomkilladj);
 		task_lock(current);
@@ -519,7 +519,7 @@ static void __out_of_memory(gfp_t gfp_ma

 	if (sysctl_oom_kill_allocating_task)
 		if (!oom_kill_process(current, gfp_mask, order, 0, NULL,
-				"Out of memory (oom_kill_allocating_task)"))
+				"Failure to reclaim enough memory (oom_kill_allocating_task)"))
 			return;
 retry:
 	/*
@@ -534,11 +534,11 @@ retry:
 	/* Found nothing?!?! Either we hang forever, or we panic. */
 	if (!p) {
 		read_unlock(&tasklist_lock);
-		panic("Out of memory and no killable processes...\n");
+		panic("Failure to reclaim enough memory and no killable processes...\n");
 	}

 	if (oom_kill_process(p, gfp_mask, order, points, NULL,
-			     "Out of memory"))
+			     "Memory reclaim failure"))
 		goto retry;
 }

@@ -563,7 +563,7 @@ void pagefault_out_of_memory(void)
 		goto rest_and_return;

 	if (sysctl_panic_on_oom)
-		panic("out of memory from page fault. panic_on_oom is selected.\n");
+		panic("failure to reclaim enough memory. panic_on_oom is selected.\n");

 	read_lock(&tasklist_lock);
 	__out_of_memory(0, 0); /* unknown gfp_mask and order */
@@ -600,7 +600,7 @@ void out_of_memory(struct zonelist *zone
 		return;

 	if (sysctl_panic_on_oom == 2)
-		panic("out of memory. Compulsory panic_on_oom is selected.\n");
+		panic("failure to reclaim enough memory. Compulsory panic_on_oom is selected.\n");

 	/*
 	 * Check if there were limitations on the allocation (only relevant for
@@ -617,7 +617,7 @@ void out_of_memory(struct zonelist *zone

 	case CONSTRAINT_NONE:
 		if (sysctl_panic_on_oom)
-			panic("out of memory. panic_on_oom is selected\n");
+			panic("failure to enough reclaim memory. panic_on_oom is selected\n");
 		/* Fall-through */
 	case CONSTRAINT_CPUSET:
 		__out_of_memory(gfp_mask, order);
--
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