linux-kernel - Warn when we run out of swap space (was Re: Misleading OOM messages)

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Message-ID: <alpine.DEB.1.10.0905221016340.23657@qirst.com>
Date:	Fri, 22 May 2009 10:17:15 -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: Warn when we run out of swap space (was Re: Misleading OOM
 messages)


Subject: Warn if we run out of swap space

Running out of swap space means that the evicton of anonymous pages may no longer
be possible which can lead to OOM conditions.

Print a warning when swap space first becomes exhausted.

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

---
 mm/swapfile.c |    1 +
 1 file changed, 1 insertion(+)

Index: linux-2.6/mm/swapfile.c
===================================================================
--- linux-2.6.orig/mm/swapfile.c	2009-05-22 09:07:40.000000000 -0500
+++ linux-2.6/mm/swapfile.c	2009-05-22 09:15:59.000000000 -0500
@@ -412,6 +412,7 @@ swp_entry_t get_swap_page(void)
 	nr_swap_pages++;
 noswap:
 	spin_unlock(&swap_lock);
+	WARN_ONCE(1, "All of swap is in use. Some pages cannot be swapped out.");
 	return (swp_entry_t) {0};
 }

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