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

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Message-ID: <Pine.LNX.4.64.0706081345520.2447@schroedinger.engr.sgi.com>
Date:	Fri, 8 Jun 2007 13:48:49 -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:

> > Could you remove the trylock patch and see how this one fares? We may need
> > both but this should avoid taking the slub_lock around any possible alloc of
> > sysfs.
> It's a bit tricky

Hmmm... Yes that version was aginst 4-mm1 instead after the defrag 
patchset. The difference is only the "ops" parameter...

Rediff to apply after defrag patchset.

SLUB: Move sysfs operations outside of slub_lock

Sysfs can do a gazillion things when called. Make sure that we do
not call any sysfs functions while holding the slub_lock. Let sysfs
fend for itself locking wise.

Just protect the essentials: The modifications to the slab lists
and the ref counters of the slabs.

Signed-off-by: Christoph Lameter <clameter@....com>

---
 mm/slub.c |   34 +++++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 13 deletions(-)

Index: slub/mm/slub.c
===================================================================
--- slub.orig/mm/slub.c	2007-06-08 13:47:32.000000000 -0700
+++ slub/mm/slub.c	2007-06-08 13:48:07.000000000 -0700
@@ -2193,12 +2193,13 @@ void kmem_cache_destroy(struct kmem_cach
 	s->refcount--;
 	if (!s->refcount) {
 		list_del(&s->list);
+		up_write(&slub_lock);
 		if (kmem_cache_close(s))
 			WARN_ON(1);
 		sysfs_slab_remove(s);
 		kfree(s);
-	}
-	up_write(&slub_lock);
+	} else
+		up_write(&slub_lock);
 }
 EXPORT_SYMBOL(kmem_cache_destroy);
 
@@ -2956,26 +2957,33 @@ struct kmem_cache *kmem_cache_create(con
 		 */
 		s->objsize = max(s->objsize, (int)size);
 		s->inuse = max_t(int, s->inuse, ALIGN(size, sizeof(void *)));
+		up_write(&slub_lock);
+
 		if (sysfs_slab_alias(s, name))
 			goto err;
-	} else {
-		s = kmalloc(kmem_size, GFP_KERNEL);
-		if (s && kmem_cache_open(s, GFP_KERNEL, name,
+
+		return s;
+	}
+
+	s = kmalloc(kmem_size, GFP_KERNEL);
+	if (s) {
+		if (kmem_cache_open(s, GFP_KERNEL, name,
 				size, align, flags, ctor, ops)) {
-			if (sysfs_slab_add(s)) {
-				kfree(s);
-				goto err;
-			}
 			list_add(&s->list, &slab_caches);
+			up_write(&slub_lock);
 			raise_kswapd_order(s->order);
-		} else
-			kfree(s);
+
+			if (sysfs_slab_add(s))
+				goto err;
+
+			return s;
+
+		}
+		kfree(s);
 	}
 	up_write(&slub_lock);
-	return s;
 
 err:
-	up_write(&slub_lock);
 	if (flags & SLAB_PANIC)
 		panic("Cannot create slabcache %s\n", name);
 	else
-
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