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debugobjects: Implement batch processing

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Adding and removing single objects in a loop is bad in terms of lock
contention and cache line accesses.

To implement batching, record the last object in a batch in the object
itself. This is trivialy possible as hlists are strictly stacks. At a batch
boundary, when the first object is added to the list the object stores a
pointer to itself in debug_obj::batch_last. When the next object is added
to the list then the batch_last pointer is retrieved from the first object
in the list and stored in the to be added one.

That means for batch processing the first object always has a pointer to
the last object in a batch, which allows to move batches in a cache line
efficient way and reduces the lock held time.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Zhen Lei <thunder.leizhen@huawei.com>
Link: https://lore.kernel.org/all/20241007164914.258995000@linutronix.de
This commit is contained in:
Thomas Gleixner 2024-10-07 18:50:17 +02:00
parent aebbfe0779
commit f57ebb92ba
1 changed files with 46 additions and 15 deletions
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61
lib/debugobjects.c
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@ -149,18 +149,31 @@ static __always_inline bool pool_must_refill(struct obj_pool *pool)
static bool pool_move_batch(struct obj_pool *dst, struct obj_pool *src)
{
if (dst->cnt + ODEBUG_BATCH_SIZE > dst->max_cnt || !src->cnt)
struct hlist_node *last, *next_batch, *first_batch;
struct debug_obj *obj;
if (dst->cnt >= dst->max_cnt || !src->cnt)
return false;
for (int i = 0; i < ODEBUG_BATCH_SIZE && src->cnt; i++) {
struct hlist_node *node = src->objects.first;
first_batch = src->objects.first;
obj = hlist_entry(first_batch, typeof(*obj), node);
last = obj->batch_last;
next_batch = last->next;
WRITE_ONCE(src->cnt, src->cnt - 1);
WRITE_ONCE(dst->cnt, dst->cnt + 1);
/* Move the next batch to the front of the source pool */
src->objects.first = next_batch;
if (next_batch)
next_batch->pprev = &src->objects.first;
hlist_del(node);
hlist_add_head(node, &dst->objects);
}
/* Add the extracted batch to the destination pool */
last->next = dst->objects.first;
if (last->next)
last->next->pprev = &last->next;
first_batch->pprev = &dst->objects.first;
dst->objects.first = first_batch;
WRITE_ONCE(src->cnt, src->cnt - ODEBUG_BATCH_SIZE);
WRITE_ONCE(dst->cnt, dst->cnt + ODEBUG_BATCH_SIZE);
return true;
}
@ -182,16 +195,27 @@ static bool pool_push_batch(struct obj_pool *dst, struct hlist_head *head)
static bool pool_pop_batch(struct hlist_head *head, struct obj_pool *src)
{
struct hlist_node *last, *next;
struct debug_obj *obj;
if (!src->cnt)
return false;
for (int i = 0; src->cnt && i < ODEBUG_BATCH_SIZE; i++) {
struct hlist_node *node = src->objects.first;
/* Move the complete list to the head */
hlist_move_list(&src->objects, head);
WRITE_ONCE(src->cnt, src->cnt - 1);
hlist_del(node);
hlist_add_head(node, head);
}
obj = hlist_entry(head->first, typeof(*obj), node);
last = obj->batch_last;
next = last->next;
/* Disconnect the batch from the list */
last->next = NULL;
/* Move the node after last back to the source pool. */
src->objects.first = next;
if (next)
next->pprev = &src->objects.first;
WRITE_ONCE(src->cnt, src->cnt - ODEBUG_BATCH_SIZE);
return true;
}
@ -226,7 +250,7 @@ static struct debug_obj *pcpu_alloc(void)
if (!pool_move_batch(pcp, &pool_global))
return NULL;
}
obj_pool_used += pcp->cnt;
obj_pool_used += ODEBUG_BATCH_SIZE;
if (obj_pool_used > obj_pool_max_used)
obj_pool_max_used = obj_pool_used;
@ -239,9 +263,16 @@ static struct debug_obj *pcpu_alloc(void)
static void pcpu_free(struct debug_obj *obj)
{
struct obj_pool *pcp = this_cpu_ptr(&pool_pcpu);
struct debug_obj *first;
lockdep_assert_irqs_disabled();
if (!(pcp->cnt % ODEBUG_BATCH_SIZE)) {
obj->batch_last = &obj->node;
} else {
first = hlist_entry(pcp->objects.first, typeof(*first), node);
obj->batch_last = first->batch_last;
}
hlist_add_head(&obj->node, &pcp->objects);
pcp->cnt++;