Commit 15b7c514 authored Oct 02, 2010 by Pekka Enberg

SLUB: Optimize slab_free() debug check



This patch optimizes slab_free() debug check to use "c->node != NUMA_NO_NODE"
instead of "c->node >= 0" because the former generates smaller code on x86-64:

  Before:

    4736:       48 39 70 08             cmp    %rsi,0x8(%rax)
    473a:       75 26                   jne    4762 <kfree+0xa2>
    473c:       44 8b 48 10             mov    0x10(%rax),%r9d
    4740:       45 85 c9                test   %r9d,%r9d
    4743:       78 1d                   js     4762 <kfree+0xa2>

  After:

    4736:       48 39 70 08             cmp    %rsi,0x8(%rax)
    473a:       75 23                   jne    475f <kfree+0x9f>
    473c:       83 78 10 ff             cmpl   $0xffffffffffffffff,0x10(%rax)
    4740:       74 1d                   je     475f <kfree+0x9f>

This patch also cleans up __slab_alloc() to use NUMA_NO_NODE instead of "-1"
for enabling debugging for a per-CPU cache.

Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

parent 5d1f57e4

mm/slub.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1718,7 +1718,7 @@ debug:

		c->page->inuse++;
		c->page->freelist = get_freepointer(s, object);
		c->node = -1;
		c->node = NUMA_NO_NODE;
		goto unlock_out;
		}

		@@ -1895,7 +1895,7 @@ static __always_inline void slab_free(struct kmem_cache *s,

		slab_free_hook_irq(s, x);

		if (likely(page == c->page && c->node >= 0)) {
		if (likely(page == c->page && c->node != NUMA_NO_NODE)) {
		set_freepointer(s, object, c->freelist);
		c->freelist = object;
		stat(s, FREE_FASTPATH);

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