linux-kernel - Re: [patch 00/12] Slab defragmentation V3

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Message-ID: <Pine.LNX.4.64.0706081110580.1464@schroedinger.engr.sgi.com>
Date:	Fri, 8 Jun 2007 11:16:13 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Michal Piotrowski <michal.k.k.piotrowski@...il.com>
cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, dgc@....com, Mel Gorman <mel@...net.ie>
Subject: Re: [patch 00/12] Slab defragmentation V3

On Fri, 8 Jun 2007, Michal Piotrowski wrote:

> bash shared mapping + your script in a loop
> while true;  do sudo ./run.sh; done > res3.txt

Hmmmm... Seems to be triggered from the reclaim path kmem_cache_defrag 
rather than the manual triggered one from the script. Taking the slub_lock 
on the reclaim path is an issue it seems.

Maybe we need to do a trylock in kmem_cache_defrag to defuse the 
situation? This is after all an optimization so we can bug out.

Does this fix it?

---
 mm/slub.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Index: slub/mm/slub.c
===================================================================
--- slub.orig/mm/slub.c	2007-06-08 11:12:40.000000000 -0700
+++ slub/mm/slub.c	2007-06-08 11:14:34.000000000 -0700
@@ -2738,7 +2738,9 @@ int kmem_cache_defrag(int percent, int n
 	unsigned long pages = 0;
 	void *scratch;
 
-	down_read(&slub_lock);
+	if (!down_read_trylock(&slub_lock))
+		return 0;
+
 	list_for_each_entry(s, &slab_caches, list) {
 
 		/*


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