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Subject[slubllv3 11/21] slub: Add cmpxchg_double_slab()
Add a function that operates on the second doubleword in the page struct
and manipulates the object counters, the freelist and the frozen attribute.

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

---
include/linux/slub_def.h | 1 +
mm/slub.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 46 insertions(+)
Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c 2011-04-15 13:14:40.000000000 -0500
+++ linux-2.6/mm/slub.c 2011-04-15 13:14:51.000000000 -0500
@@ -131,6 +131,9 @@ static inline int kmem_cache_debug(struc
/* Enable to test recovery from slab corruption on boot */
#undef SLUB_RESILIENCY_TEST

+/* Enable to log cmpxchg failures */
+#undef SLUB_DEBUG_CMPXCHG
+
/*
* Mininum number of partial slabs. These will be left on the partial
* lists even if they are empty. kmem_cache_shrink may reclaim them.
@@ -170,6 +173,7 @@ static inline int kmem_cache_debug(struc

/* Internal SLUB flags */
#define __OBJECT_POISON 0x80000000UL /* Poison object */
+#define __CMPXCHG_DOUBLE 0x40000000UL /* Use cmpxchg_double */

static int kmem_size = sizeof(struct kmem_cache);

@@ -326,6 +330,37 @@ static inline int oo_objects(struct kmem
return x.x & OO_MASK;
}

+static inline bool cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
+ void *freelist_old, unsigned long counters_old,
+ void *freelist_new, unsigned long counters_new,
+ const char *n)
+{
+#ifdef CONFIG_CMPXCHG_DOUBLE
+ if (s->flags & __CMPXCHG_DOUBLE) {
+ if (cmpxchg_double(&page->freelist,
+ freelist_old, counters_old,
+ freelist_new, counters_new))
+ return 1;
+ } else
+#endif
+ {
+ if (page->freelist == freelist_old && page->counters == counters_old) {
+ page->freelist = freelist_new;
+ page->counters = counters_new;
+ return 1;
+ }
+ }
+
+ cpu_relax();
+ stat(s, CMPXCHG_DOUBLE_FAIL);
+
+#ifdef SLUB_DEBUG_CMPXCHG
+ printk(KERN_INFO "%s %s: cmpxchg double redo ", n, s->name);
+#endif
+
+ return 0;
+}
+
/*
* Determine a map of object in use on a page.
*
@@ -2654,6 +2689,12 @@ static int kmem_cache_open(struct kmem_c
}
}

+#ifdef CONFIG_CMPXCHG_DOUBLE
+ if (system_has_cmpxchg_double() && (s->flags & SLAB_DEBUG_FLAGS) == 0)
+ /* Enable fast mode */
+ s->flags |= __CMPXCHG_DOUBLE;
+#endif
+
/*
* The larger the object size is, the more pages we want on the partial
* list to avoid pounding the page allocator excessively.
@@ -4551,6 +4592,8 @@ STAT_ATTR(DEACTIVATE_TO_HEAD, deactivate
STAT_ATTR(DEACTIVATE_TO_TAIL, deactivate_to_tail);
STAT_ATTR(DEACTIVATE_REMOTE_FREES, deactivate_remote_frees);
STAT_ATTR(ORDER_FALLBACK, order_fallback);
+STAT_ATTR(CMPXCHG_DOUBLE_CPU_FAIL, cmpxchg_double_cpu_fail);
+STAT_ATTR(CMPXCHG_DOUBLE_FAIL, cmpxchg_double_fail);
#endif

static struct attribute *slab_attrs[] = {
@@ -4608,6 +4651,8 @@ static struct attribute *slab_attrs[] =
&deactivate_to_tail_attr.attr,
&deactivate_remote_frees_attr.attr,
&order_fallback_attr.attr,
+ &cmpxchg_double_fail_attr.attr,
+ &cmpxchg_double_cpu_fail_attr.attr,
#endif
#ifdef CONFIG_FAILSLAB
&failslab_attr.attr,
Index: linux-2.6/include/linux/slub_def.h
===================================================================
--- linux-2.6.orig/include/linux/slub_def.h 2011-04-13 15:19:53.000000000 -0500
+++ linux-2.6/include/linux/slub_def.h 2011-04-15 13:14:51.000000000 -0500
@@ -33,6 +33,7 @@ enum stat_item {
DEACTIVATE_REMOTE_FREES,/* Slab contained remotely freed objects */
ORDER_FALLBACK, /* Number of times fallback was necessary */
CMPXCHG_DOUBLE_CPU_FAIL,/* Failure of this_cpu_cmpxchg_double */
+ CMPXCHG_DOUBLE_FAIL, /* Number of times that cmpxchg double did not match */
NR_SLUB_STAT_ITEMS };

struct kmem_cache_cpu {


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