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slub: explicit list_lock taking
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The allocator fastpath rework does change the usage of the list_lock.
Remove the list_lock processing from the functions that hide them from the
critical sections and move them into those critical sections.

This in turn simplifies the support functions (no __ variant needed anymore)
and simplifies the lock handling on bootstrap.

Inline add_partial since it becomes pretty simple.

Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
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Christoph Lameter authored and Pekka Enberg committed Jul 2, 2011
1 parent b789ef5 commit 5cc6eee
Showing 1 changed file with 49 additions and 40 deletions.
89 changes: 49 additions & 40 deletions mm/slub.c
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Original file line number Diff line number Diff line change
Expand Up @@ -916,26 +916,27 @@ static inline void slab_free_hook(struct kmem_cache *s, void *x)

/*
* Tracking of fully allocated slabs for debugging purposes.
*
* list_lock must be held.
*/
static void add_full(struct kmem_cache_node *n, struct page *page)
static void add_full(struct kmem_cache *s,
struct kmem_cache_node *n, struct page *page)
{
spin_lock(&n->list_lock);
if (!(s->flags & SLAB_STORE_USER))
return;

list_add(&page->lru, &n->full);
spin_unlock(&n->list_lock);
}

/*
* list_lock must be held.
*/
static void remove_full(struct kmem_cache *s, struct page *page)
{
struct kmem_cache_node *n;

if (!(s->flags & SLAB_STORE_USER))
return;

n = get_node(s, page_to_nid(page));

spin_lock(&n->list_lock);
list_del(&page->lru);
spin_unlock(&n->list_lock);
}

/* Tracking of the number of slabs for debugging purposes */
Expand Down Expand Up @@ -1060,8 +1061,13 @@ static noinline int free_debug_processing(struct kmem_cache *s,
}

/* Special debug activities for freeing objects */
if (!page->frozen && !page->freelist)
if (!page->frozen && !page->freelist) {
struct kmem_cache_node *n = get_node(s, page_to_nid(page));

spin_lock(&n->list_lock);
remove_full(s, page);
spin_unlock(&n->list_lock);
}
if (s->flags & SLAB_STORE_USER)
set_track(s, object, TRACK_FREE, addr);
trace(s, page, object, 0);
Expand Down Expand Up @@ -1170,7 +1176,8 @@ static inline int slab_pad_check(struct kmem_cache *s, struct page *page)
{ return 1; }
static inline int check_object(struct kmem_cache *s, struct page *page,
void *object, u8 val) { return 1; }
static inline void add_full(struct kmem_cache_node *n, struct page *page) {}
static inline void add_full(struct kmem_cache *s, struct kmem_cache_node *n,
struct page *page) {}
static inline unsigned long kmem_cache_flags(unsigned long objsize,
unsigned long flags, const char *name,
void (*ctor)(void *))
Expand Down Expand Up @@ -1420,46 +1427,41 @@ static __always_inline int slab_trylock(struct page *page)
}

/*
* Management of partially allocated slabs
* Management of partially allocated slabs.
*
* list_lock must be held.
*/
static void add_partial(struct kmem_cache_node *n,
static inline void add_partial(struct kmem_cache_node *n,
struct page *page, int tail)
{
spin_lock(&n->list_lock);
n->nr_partial++;
if (tail)
list_add_tail(&page->lru, &n->partial);
else
list_add(&page->lru, &n->partial);
spin_unlock(&n->list_lock);
}

static inline void __remove_partial(struct kmem_cache_node *n,
/*
* list_lock must be held.
*/
static inline void remove_partial(struct kmem_cache_node *n,
struct page *page)
{
list_del(&page->lru);
n->nr_partial--;
}

static void remove_partial(struct kmem_cache *s, struct page *page)
{
struct kmem_cache_node *n = get_node(s, page_to_nid(page));

spin_lock(&n->list_lock);
__remove_partial(n, page);
spin_unlock(&n->list_lock);
}

/*
* Lock slab and remove from the partial list.
* Lock slab, remove from the partial list and put the object into the
* per cpu freelist.
*
* Must hold list_lock.
*/
static inline int lock_and_freeze_slab(struct kmem_cache_node *n,
struct page *page)
{
if (slab_trylock(page)) {
__remove_partial(n, page);
remove_partial(n, page);
return 1;
}
return 0;
Expand Down Expand Up @@ -1576,12 +1578,17 @@ static void unfreeze_slab(struct kmem_cache *s, struct page *page, int tail)
if (page->inuse) {

if (page->freelist) {
spin_lock(&n->list_lock);
add_partial(n, page, tail);
spin_unlock(&n->list_lock);
stat(s, tail ? DEACTIVATE_TO_TAIL : DEACTIVATE_TO_HEAD);
} else {
stat(s, DEACTIVATE_FULL);
if (kmem_cache_debug(s) && (s->flags & SLAB_STORE_USER))
add_full(n, page);
if (kmem_cache_debug(s) && (s->flags & SLAB_STORE_USER)) {
spin_lock(&n->list_lock);
add_full(s, n, page);
spin_unlock(&n->list_lock);
}
}
slab_unlock(page);
} else {
Expand All @@ -1597,7 +1604,9 @@ static void unfreeze_slab(struct kmem_cache *s, struct page *page, int tail)
* kmem_cache_shrink can reclaim any empty slabs from
* the partial list.
*/
spin_lock(&n->list_lock);
add_partial(n, page, 1);
spin_unlock(&n->list_lock);
slab_unlock(page);
} else {
slab_unlock(page);
Expand Down Expand Up @@ -2099,7 +2108,11 @@ static void __slab_free(struct kmem_cache *s, struct page *page,
* then add it.
*/
if (unlikely(!prior)) {
struct kmem_cache_node *n = get_node(s, page_to_nid(page));

spin_lock(&n->list_lock);
add_partial(get_node(s, page_to_nid(page)), page, 1);
spin_unlock(&n->list_lock);
stat(s, FREE_ADD_PARTIAL);
}

Expand All @@ -2113,7 +2126,11 @@ static void __slab_free(struct kmem_cache *s, struct page *page,
/*
* Slab still on the partial list.
*/
remove_partial(s, page);
struct kmem_cache_node *n = get_node(s, page_to_nid(page));

spin_lock(&n->list_lock);
remove_partial(n, page);
spin_unlock(&n->list_lock);
stat(s, FREE_REMOVE_PARTIAL);
}
slab_unlock(page);
Expand Down Expand Up @@ -2391,7 +2408,6 @@ static void early_kmem_cache_node_alloc(int node)
{
struct page *page;
struct kmem_cache_node *n;
unsigned long flags;

BUG_ON(kmem_cache_node->size < sizeof(struct kmem_cache_node));

Expand All @@ -2418,14 +2434,7 @@ static void early_kmem_cache_node_alloc(int node)
init_kmem_cache_node(n, kmem_cache_node);
inc_slabs_node(kmem_cache_node, node, page->objects);

/*
* lockdep requires consistent irq usage for each lock
* so even though there cannot be a race this early in
* the boot sequence, we still disable irqs.
*/
local_irq_save(flags);
add_partial(n, page, 0);
local_irq_restore(flags);
}

static void free_kmem_cache_nodes(struct kmem_cache *s)
Expand Down Expand Up @@ -2709,7 +2718,7 @@ static void free_partial(struct kmem_cache *s, struct kmem_cache_node *n)
spin_lock_irqsave(&n->list_lock, flags);
list_for_each_entry_safe(page, h, &n->partial, lru) {
if (!page->inuse) {
__remove_partial(n, page);
remove_partial(n, page);
discard_slab(s, page);
} else {
list_slab_objects(s, page,
Expand Down Expand Up @@ -3047,7 +3056,7 @@ int kmem_cache_shrink(struct kmem_cache *s)
* may have freed the last object and be
* waiting to release the slab.
*/
__remove_partial(n, page);
remove_partial(n, page);
slab_unlock(page);
discard_slab(s, page);
} else {
Expand Down

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