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authorPekka Enberg <penberg@cs.helsinki.fi>2009-02-20 12:21:33 +0200
committerPekka Enberg <penberg@cs.helsinki.fi>2009-02-20 12:25:47 +0200
commit51735a7ca67531267a27b57e5fe20f7815192f9c (patch)
tree35c2f72b18b168f8f9c8d7f7b1172422f0a16238
parentffadd4d0feb5376c82dc3a4104731b7ce2794edc (diff)
SLUB: Do not pass 8k objects through to the page allocator
Increase the maximum object size in SLUB so that 8k objects are not passed through to the page allocator anymore. The network stack uses 8k objects for performance critical operations. The patch is motivated by a SLAB vs. SLUB regression in the netperf benchmark. The problem is that the kfree(skb->head) call in skb_release_data() that is subject to page allocator pass-through as the size passed to __alloc_skb() is larger than 4 KB in this test. As explained by Yanmin Zhang: I use 2.6.29-rc2 kernel to run netperf UDP-U-4k CPU_NUM client/server pair loopback testing on x86-64 machines. Comparing with SLUB, SLAB's result is about 2.3 times of SLUB's. After applying the reverting patch, the result difference between SLUB and SLAB becomes 1% which we might consider as fluctuation. [ penberg@cs.helsinki.fi: fix oops in kmalloc() ] Reported-by: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com> Tested-by: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com> Signed-off-by: Christoph Lameter <cl@linux-foundation.org> Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
-rw-r--r--include/linux/slub_def.h4
1 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index 986e09dcfd8..e217a7a68ea 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -129,9 +129,9 @@ struct kmem_cache {
* This should be dropped to PAGE_SIZE / 2 once the page allocator
* "fastpath" becomes competitive with the slab allocator fastpaths.
*/
-#define SLUB_MAX_SIZE (PAGE_SIZE)
+#define SLUB_MAX_SIZE (2 * PAGE_SIZE)
-#define SLUB_PAGE_SHIFT (PAGE_SHIFT + 1)
+#define SLUB_PAGE_SHIFT (PAGE_SHIFT + 2)
/*
* We keep the general caches in an array of slab caches that are used for