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-rw-r--r--include/linux/mm_types.h14
-rw-r--r--include/linux/slub_def.h4
-rw-r--r--mm/slub.c339
3 files changed, 309 insertions, 48 deletions
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 774b8952deb..7870e473033 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -79,9 +79,21 @@ struct page {
};
/* Third double word block */
- struct list_head lru; /* Pageout list, eg. active_list
+ union {
+ struct list_head lru; /* Pageout list, eg. active_list
* protected by zone->lru_lock !
*/
+ struct { /* slub per cpu partial pages */
+ struct page *next; /* Next partial slab */
+#ifdef CONFIG_64BIT
+ int pages; /* Nr of partial slabs left */
+ int pobjects; /* Approximate # of objects */
+#else
+ short int pages;
+ short int pobjects;
+#endif
+ };
+ };
/* Remainder is not double word aligned */
union {
diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index f58d6413d23..4890ef79d75 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -36,12 +36,15 @@ enum stat_item {
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 */
+ CPU_PARTIAL_ALLOC, /* Used cpu partial on alloc */
+ CPU_PARTIAL_FREE, /* USed cpu partial on free */
NR_SLUB_STAT_ITEMS };
struct kmem_cache_cpu {
void **freelist; /* Pointer to next available object */
unsigned long tid; /* Globally unique transaction id */
struct page *page; /* The slab from which we are allocating */
+ struct page *partial; /* Partially allocated frozen slabs */
int node; /* The node of the page (or -1 for debug) */
#ifdef CONFIG_SLUB_STATS
unsigned stat[NR_SLUB_STAT_ITEMS];
@@ -79,6 +82,7 @@ struct kmem_cache {
int size; /* The size of an object including meta data */
int objsize; /* The size of an object without meta data */
int offset; /* Free pointer offset. */
+ int cpu_partial; /* Number of per cpu partial pages to keep around */
struct kmem_cache_order_objects oo;
/* Allocation and freeing of slabs */
diff --git a/mm/slub.c b/mm/slub.c
index df381af963b..0e286acef62 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1560,7 +1560,7 @@ static inline void remove_partial(struct kmem_cache_node *n,
*/
static inline void *acquire_slab(struct kmem_cache *s,
struct kmem_cache_node *n, struct page *page,
- struct kmem_cache_cpu *c)
+ int mode)
{
void *freelist;
unsigned long counters;
@@ -1575,7 +1575,8 @@ static inline void *acquire_slab(struct kmem_cache *s,
freelist = page->freelist;
counters = page->counters;
new.counters = counters;
- new.inuse = page->objects;
+ if (mode)
+ new.inuse = page->objects;
VM_BUG_ON(new.frozen);
new.frozen = 1;
@@ -1586,34 +1587,20 @@ static inline void *acquire_slab(struct kmem_cache *s,
"lock and freeze"));
remove_partial(n, page);
-
- if (freelist) {
- /* Populate the per cpu freelist */
- c->page = page;
- c->node = page_to_nid(page);
- stat(s, ALLOC_FROM_PARTIAL);
-
- return freelist;
- } else {
- /*
- * Slab page came from the wrong list. No object to allocate
- * from. Put it onto the correct list and continue partial
- * scan.
- */
- printk(KERN_ERR "SLUB: %s : Page without available objects on"
- " partial list\n", s->name);
- return NULL;
- }
+ return freelist;
}
+static int put_cpu_partial(struct kmem_cache *s, struct page *page, int drain);
+
/*
* Try to allocate a partial slab from a specific node.
*/
static void *get_partial_node(struct kmem_cache *s,
struct kmem_cache_node *n, struct kmem_cache_cpu *c)
{
- struct page *page;
- void *object;
+ struct page *page, *page2;
+ void *object = NULL;
+ int count = 0;
/*
* Racy check. If we mistakenly see no partial slabs then we
@@ -1625,13 +1612,28 @@ static void *get_partial_node(struct kmem_cache *s,
return NULL;
spin_lock(&n->list_lock);
- list_for_each_entry(page, &n->partial, lru) {
- object = acquire_slab(s, n, page, c);
- if (object)
- goto out;
+ list_for_each_entry_safe(page, page2, &n->partial, lru) {
+ void *t = acquire_slab(s, n, page, count == 0);
+ int available;
+
+ if (!t)
+ break;
+
+ if (!count) {
+ c->page = page;
+ c->node = page_to_nid(page);
+ stat(s, ALLOC_FROM_PARTIAL);
+ count++;
+ object = t;
+ available = page->objects - page->inuse;
+ } else {
+ page->freelist = t;
+ available = put_cpu_partial(s, page, 0);
+ }
+ if (kmem_cache_debug(s) || available > s->cpu_partial / 2)
+ break;
+
}
- object = NULL;
-out:
spin_unlock(&n->list_lock);
return object;
}
@@ -1926,6 +1928,123 @@ redo:
}
}
+/* Unfreeze all the cpu partial slabs */
+static void unfreeze_partials(struct kmem_cache *s)
+{
+ struct kmem_cache_node *n = NULL;
+ struct kmem_cache_cpu *c = this_cpu_ptr(s->cpu_slab);
+ struct page *page;
+
+ while ((page = c->partial)) {
+ enum slab_modes { M_PARTIAL, M_FREE };
+ enum slab_modes l, m;
+ struct page new;
+ struct page old;
+
+ c->partial = page->next;
+ l = M_FREE;
+
+ do {
+
+ old.freelist = page->freelist;
+ old.counters = page->counters;
+ VM_BUG_ON(!old.frozen);
+
+ new.counters = old.counters;
+ new.freelist = old.freelist;
+
+ new.frozen = 0;
+
+ if (!new.inuse && (!n || n->nr_partial < s->min_partial))
+ m = M_FREE;
+ else {
+ struct kmem_cache_node *n2 = get_node(s,
+ page_to_nid(page));
+
+ m = M_PARTIAL;
+ if (n != n2) {
+ if (n)
+ spin_unlock(&n->list_lock);
+
+ n = n2;
+ spin_lock(&n->list_lock);
+ }
+ }
+
+ if (l != m) {
+ if (l == M_PARTIAL)
+ remove_partial(n, page);
+ else
+ add_partial(n, page, 1);
+
+ l = m;
+ }
+
+ } while (!cmpxchg_double_slab(s, page,
+ old.freelist, old.counters,
+ new.freelist, new.counters,
+ "unfreezing slab"));
+
+ if (m == M_FREE) {
+ stat(s, DEACTIVATE_EMPTY);
+ discard_slab(s, page);
+ stat(s, FREE_SLAB);
+ }
+ }
+
+ if (n)
+ spin_unlock(&n->list_lock);
+}
+
+/*
+ * Put a page that was just frozen (in __slab_free) into a partial page
+ * slot if available. This is done without interrupts disabled and without
+ * preemption disabled. The cmpxchg is racy and may put the partial page
+ * onto a random cpus partial slot.
+ *
+ * If we did not find a slot then simply move all the partials to the
+ * per node partial list.
+ */
+int put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
+{
+ struct page *oldpage;
+ int pages;
+ int pobjects;
+
+ do {
+ pages = 0;
+ pobjects = 0;
+ oldpage = this_cpu_read(s->cpu_slab->partial);
+
+ if (oldpage) {
+ pobjects = oldpage->pobjects;
+ pages = oldpage->pages;
+ if (drain && pobjects > s->cpu_partial) {
+ unsigned long flags;
+ /*
+ * partial array is full. Move the existing
+ * set to the per node partial list.
+ */
+ local_irq_save(flags);
+ unfreeze_partials(s);
+ local_irq_restore(flags);
+ pobjects = 0;
+ pages = 0;
+ }
+ }
+
+ pages++;
+ pobjects += page->objects - page->inuse;
+
+ page->pages = pages;
+ page->pobjects = pobjects;
+ page->next = oldpage;
+
+ } while (this_cpu_cmpxchg(s->cpu_slab->partial, oldpage, page) != oldpage);
+ stat(s, CPU_PARTIAL_FREE);
+ return pobjects;
+}
+
static inline void flush_slab(struct kmem_cache *s, struct kmem_cache_cpu *c)
{
stat(s, CPUSLAB_FLUSH);
@@ -1941,8 +2060,12 @@ static inline void __flush_cpu_slab(struct kmem_cache *s, int cpu)
{
struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);
- if (likely(c && c->page))
- flush_slab(s, c);
+ if (likely(c)) {
+ if (c->page)
+ flush_slab(s, c);
+
+ unfreeze_partials(s);
+ }
}
static void flush_cpu_slab(void *d)
@@ -2066,8 +2189,6 @@ static inline void *new_slab_objects(struct kmem_cache *s, gfp_t flags,
* Slow path. The lockless freelist is empty or we need to perform
* debugging duties.
*
- * Interrupts are disabled.
- *
* Processing is still very fast if new objects have been freed to the
* regular freelist. In that case we simply take over the regular freelist
* as the lockless freelist and zap the regular freelist.
@@ -2100,7 +2221,7 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
if (!c->page)
goto new_slab;
-
+redo:
if (unlikely(!node_match(c, node))) {
stat(s, ALLOC_NODE_MISMATCH);
deactivate_slab(s, c);
@@ -2133,7 +2254,7 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
NULL, new.counters,
"__slab_alloc"));
- if (unlikely(!object)) {
+ if (!object) {
c->page = NULL;
stat(s, DEACTIVATE_BYPASS);
goto new_slab;
@@ -2148,6 +2269,17 @@ load_freelist:
return object;
new_slab:
+
+ if (c->partial) {
+ c->page = c->partial;
+ c->partial = c->page->next;
+ c->node = page_to_nid(c->page);
+ stat(s, CPU_PARTIAL_ALLOC);
+ c->freelist = NULL;
+ goto redo;
+ }
+
+ /* Then do expensive stuff like retrieving pages from the partial lists */
object = get_partial(s, gfpflags, node, c);
if (unlikely(!object)) {
@@ -2341,16 +2473,29 @@ static void __slab_free(struct kmem_cache *s, struct page *page,
was_frozen = new.frozen;
new.inuse--;
if ((!new.inuse || !prior) && !was_frozen && !n) {
- n = get_node(s, page_to_nid(page));
- /*
- * Speculatively acquire the list_lock.
- * If the cmpxchg does not succeed then we may
- * drop the list_lock without any processing.
- *
- * Otherwise the list_lock will synchronize with
- * other processors updating the list of slabs.
- */
- spin_lock_irqsave(&n->list_lock, flags);
+
+ if (!kmem_cache_debug(s) && !prior)
+
+ /*
+ * Slab was on no list before and will be partially empty
+ * We can defer the list move and instead freeze it.
+ */
+ new.frozen = 1;
+
+ else { /* Needs to be taken off a list */
+
+ n = get_node(s, page_to_nid(page));
+ /*
+ * Speculatively acquire the list_lock.
+ * If the cmpxchg does not succeed then we may
+ * drop the list_lock without any processing.
+ *
+ * Otherwise the list_lock will synchronize with
+ * other processors updating the list of slabs.
+ */
+ spin_lock_irqsave(&n->list_lock, flags);
+
+ }
}
inuse = new.inuse;
@@ -2360,7 +2505,15 @@ static void __slab_free(struct kmem_cache *s, struct page *page,
"__slab_free"));
if (likely(!n)) {
- /*
+
+ /*
+ * If we just froze the page then put it onto the
+ * per cpu partial list.
+ */
+ if (new.frozen && !was_frozen)
+ put_cpu_partial(s, page, 1);
+
+ /*
* The list lock was not taken therefore no list
* activity can be necessary.
*/
@@ -2429,7 +2582,6 @@ static __always_inline void slab_free(struct kmem_cache *s,
slab_free_hook(s, x);
redo:
-
/*
* Determine the currently cpus per cpu slab.
* The cpu may change afterward. However that does not matter since
@@ -2919,7 +3071,34 @@ static int kmem_cache_open(struct kmem_cache *s,
* The larger the object size is, the more pages we want on the partial
* list to avoid pounding the page allocator excessively.
*/
- set_min_partial(s, ilog2(s->size));
+ set_min_partial(s, ilog2(s->size) / 2);
+
+ /*
+ * cpu_partial determined the maximum number of objects kept in the
+ * per cpu partial lists of a processor.
+ *
+ * Per cpu partial lists mainly contain slabs that just have one
+ * object freed. If they are used for allocation then they can be
+ * filled up again with minimal effort. The slab will never hit the
+ * per node partial lists and therefore no locking will be required.
+ *
+ * This setting also determines
+ *
+ * A) The number of objects from per cpu partial slabs dumped to the
+ * per node list when we reach the limit.
+ * B) The number of objects in partial partial slabs to extract from the
+ * per node list when we run out of per cpu objects. We only fetch 50%
+ * to keep some capacity around for frees.
+ */
+ if (s->size >= PAGE_SIZE)
+ s->cpu_partial = 2;
+ else if (s->size >= 1024)
+ s->cpu_partial = 6;
+ else if (s->size >= 256)
+ s->cpu_partial = 13;
+ else
+ s->cpu_partial = 30;
+
s->refcount = 1;
#ifdef CONFIG_NUMA
s->remote_node_defrag_ratio = 1000;
@@ -4327,6 +4506,7 @@ static ssize_t show_slab_objects(struct kmem_cache *s,
for_each_possible_cpu(cpu) {
struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);
+ struct page *page;
if (!c || c->node < 0)
continue;
@@ -4342,6 +4522,13 @@ static ssize_t show_slab_objects(struct kmem_cache *s,
total += x;
nodes[c->node] += x;
}
+ page = c->partial;
+
+ if (page) {
+ x = page->pobjects;
+ total += x;
+ nodes[c->node] += x;
+ }
per_cpu[c->node]++;
}
}
@@ -4493,6 +4680,27 @@ static ssize_t min_partial_store(struct kmem_cache *s, const char *buf,
}
SLAB_ATTR(min_partial);
+static ssize_t cpu_partial_show(struct kmem_cache *s, char *buf)
+{
+ return sprintf(buf, "%u\n", s->cpu_partial);
+}
+
+static ssize_t cpu_partial_store(struct kmem_cache *s, const char *buf,
+ size_t length)
+{
+ unsigned long objects;
+ int err;
+
+ err = strict_strtoul(buf, 10, &objects);
+ if (err)
+ return err;
+
+ s->cpu_partial = objects;
+ flush_all(s);
+ return length;
+}
+SLAB_ATTR(cpu_partial);
+
static ssize_t ctor_show(struct kmem_cache *s, char *buf)
{
if (!s->ctor)
@@ -4531,6 +4739,37 @@ static ssize_t objects_partial_show(struct kmem_cache *s, char *buf)
}
SLAB_ATTR_RO(objects_partial);
+static ssize_t slabs_cpu_partial_show(struct kmem_cache *s, char *buf)
+{
+ int objects = 0;
+ int pages = 0;
+ int cpu;
+ int len;
+
+ for_each_online_cpu(cpu) {
+ struct page *page = per_cpu_ptr(s->cpu_slab, cpu)->partial;
+
+ if (page) {
+ pages += page->pages;
+ objects += page->pobjects;
+ }
+ }
+
+ len = sprintf(buf, "%d(%d)", objects, pages);
+
+#ifdef CONFIG_SMP
+ for_each_online_cpu(cpu) {
+ struct page *page = per_cpu_ptr(s->cpu_slab, cpu) ->partial;
+
+ if (page && len < PAGE_SIZE - 20)
+ len += sprintf(buf + len, " C%d=%d(%d)", cpu,
+ page->pobjects, page->pages);
+ }
+#endif
+ return len + sprintf(buf + len, "\n");
+}
+SLAB_ATTR_RO(slabs_cpu_partial);
+
static ssize_t reclaim_account_show(struct kmem_cache *s, char *buf)
{
return sprintf(buf, "%d\n", !!(s->flags & SLAB_RECLAIM_ACCOUNT));
@@ -4853,6 +5092,8 @@ STAT_ATTR(DEACTIVATE_BYPASS, deactivate_bypass);
STAT_ATTR(ORDER_FALLBACK, order_fallback);
STAT_ATTR(CMPXCHG_DOUBLE_CPU_FAIL, cmpxchg_double_cpu_fail);
STAT_ATTR(CMPXCHG_DOUBLE_FAIL, cmpxchg_double_fail);
+STAT_ATTR(CPU_PARTIAL_ALLOC, cpu_partial_alloc);
+STAT_ATTR(CPU_PARTIAL_FREE, cpu_partial_free);
#endif
static struct attribute *slab_attrs[] = {
@@ -4861,6 +5102,7 @@ static struct attribute *slab_attrs[] = {
&objs_per_slab_attr.attr,
&order_attr.attr,
&min_partial_attr.attr,
+ &cpu_partial_attr.attr,
&objects_attr.attr,
&objects_partial_attr.attr,
&partial_attr.attr,
@@ -4873,6 +5115,7 @@ static struct attribute *slab_attrs[] = {
&destroy_by_rcu_attr.attr,
&shrink_attr.attr,
&reserved_attr.attr,
+ &slabs_cpu_partial_attr.attr,
#ifdef CONFIG_SLUB_DEBUG
&total_objects_attr.attr,
&slabs_attr.attr,
@@ -4914,6 +5157,8 @@ static struct attribute *slab_attrs[] = {
&order_fallback_attr.attr,
&cmpxchg_double_fail_attr.attr,
&cmpxchg_double_cpu_fail_attr.attr,
+ &cpu_partial_alloc_attr.attr,
+ &cpu_partial_free_attr.attr,
#endif
#ifdef CONFIG_FAILSLAB
&failslab_attr.attr,
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2024-12-02 21:58:30 +0000