slub: per cpu cache for partial pages (49e22585) · Commits · 戴 / test

include/linux/mm_types.h

+13 −1

Original line number	Diff line number	Diff line
		@@ -79,9 +79,21 @@ struct page {
		};

		/* Third double word block */
		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 {

include/linux/slub_def.h

+4 −0

Original line number	Diff line number	Diff line
		@@ -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 */

mm/slub.c

+292 −47

Original line number	Diff line number	Diff line
		@@ -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;
		@@ -1575,6 +1575,7 @@ static inline void acquire_slab(struct kmem_cache s,
		freelist = page->freelist;
		counters = page->counters;
		new.counters = counters;
		if (mode)
		new.inuse = page->objects;

		VM_BUG_ON(new.frozen);
		@@ -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;
		}
		}

		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))
		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)) {
		@@ -2341,6 +2473,17 @@ static void __slab_free(struct kmem_cache s, struct page page,
		was_frozen = new.frozen;
		new.inuse--;
		if ((!new.inuse \|\| !prior) && !was_frozen && !n) {

		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.
		@@ -2351,6 +2494,8 @@ static void __slab_free(struct kmem_cache s, struct page page,
		* other processors updating the list of slabs.
		*/
		spin_lock_irqsave(&n->list_lock, flags);

		}
		}
		inuse = new.inuse;

		@@ -2360,6 +2505,14 @@ 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,

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