Kernel/linux-next
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git synced 2024-12-29 17:22:07 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

debugobjects: Reduce parallel pool fill attempts

Browse Source 
The contention on the global pool_lock can be massive when the global pool
needs to be refilled and many CPUs try to handle this.

Address this by:

  - splitting the refill from free list and allocation.

    Refill from free list has no constraints vs. the context on RT, so
    it can be tried outside of the RT specific preemptible() guard

  - Let only one CPU handle the free list

  - Let only one CPU do allocations unless the pool level is below
    half of the minimum fill level.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240911083521.2257-4-thunder.leizhen@huawei.com-
Link: https://lore.kernel.org/all/20241007164913.582118421@linutronix.de

--
 lib/debugobjects.c |   84 +++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 59 insertions(+), 25 deletions(-)
This commit is contained in:
Zhen Lei 2024-10-07 18:50:03 +02:00 committed by Thomas Gleixner
parent 661cc28b52
commit d8c6cd3a5c
1 changed files with 61 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

88
lib/debugobjects.c
View File

@ -138,14 +138,10 @@ static void free_object_list(struct hlist_head *head)
debug_objects_freed += cnt;
}
static void fill_pool(void)
static void fill_pool_from_freelist(void)
{
gfp_t gfp = __GFP_HIGH | __GFP_NOWARN;
static unsigned long state;
struct debug_obj *obj;
unsigned long flags;
if (likely(READ_ONCE(obj_pool_free) >= debug_objects_pool_min_level))
return;
/*
* Reuse objs from the global obj_to_free list; they will be
@ -154,32 +150,58 @@ static void fill_pool(void)
* obj_nr_tofree is checked locklessly; the READ_ONCE() pairs with
* the WRITE_ONCE() in pool_lock critical sections.
*/
if (READ_ONCE(obj_nr_tofree)) {
raw_spin_lock_irqsave(&pool_lock, flags);
/*
* Recheck with the lock held as the worker thread might have
* won the race and freed the global free list already.
*/
while (obj_nr_tofree && (obj_pool_free < debug_objects_pool_min_level)) {
obj = hlist_entry(obj_to_free.first, typeof(*obj), node);
hlist_del(&obj->node);
WRITE_ONCE(obj_nr_tofree, obj_nr_tofree - 1);
hlist_add_head(&obj->node, &obj_pool);
WRITE_ONCE(obj_pool_free, obj_pool_free + 1);
}
raw_spin_unlock_irqrestore(&pool_lock, flags);
}
if (unlikely(!obj_cache))
if (!READ_ONCE(obj_nr_tofree))
return;
/*
* Prevent the context from being scheduled or interrupted after
* setting the state flag;
*/
guard(irqsave)();
/*
* Avoid lock contention on &pool_lock and avoid making the cache
* line exclusive by testing the bit before attempting to set it.
*/
if (test_bit(0, &state) || test_and_set_bit(0, &state))
return;
guard(raw_spinlock)(&pool_lock);
/*
* Recheck with the lock held as the worker thread might have
* won the race and freed the global free list already.
*/
while (obj_nr_tofree && (obj_pool_free < debug_objects_pool_min_level)) {
obj = hlist_entry(obj_to_free.first, typeof(*obj), node);
hlist_del(&obj->node);
WRITE_ONCE(obj_nr_tofree, obj_nr_tofree - 1);
hlist_add_head(&obj->node, &obj_pool);
WRITE_ONCE(obj_pool_free, obj_pool_free + 1);
}
clear_bit(0, &state);
}
static void fill_pool(void)
{
static atomic_t cpus_allocating;
/*
* Avoid allocation and lock contention when:
* - One other CPU is already allocating
* - the global pool has not reached the critical level yet
*/
if (READ_ONCE(obj_pool_free) > (debug_objects_pool_min_level / 2) &&
atomic_read(&cpus_allocating))
return;
atomic_inc(&cpus_allocating);
while (READ_ONCE(obj_pool_free) < debug_objects_pool_min_level) {
struct debug_obj *new, *last = NULL;
HLIST_HEAD(head);
int cnt;
for (cnt = 0; cnt < ODEBUG_BATCH_SIZE; cnt++) {
new = kmem_cache_zalloc(obj_cache, gfp);
new = kmem_cache_zalloc(obj_cache, __GFP_HIGH | __GFP_NOWARN);
if (!new)
break;
hlist_add_head(&new->node, &head);
@ -187,14 +209,14 @@ static void fill_pool(void)
last = new;
}
if (!cnt)
return;
break;
raw_spin_lock_irqsave(&pool_lock, flags);
guard(raw_spinlock_irqsave)(&pool_lock);
hlist_splice_init(&head, &last->node, &obj_pool);
debug_objects_allocated += cnt;
WRITE_ONCE(obj_pool_free, obj_pool_free + cnt);
raw_spin_unlock_irqrestore(&pool_lock, flags);
}
atomic_dec(&cpus_allocating);
}
/*
@ -597,6 +619,18 @@ static struct debug_obj *lookup_object_or_alloc(void *addr, struct debug_bucket
static void debug_objects_fill_pool(void)
{
if (unlikely(!obj_cache))
return;
if (likely(READ_ONCE(obj_pool_free) >= debug_objects_pool_min_level))
return;
/* Try reusing objects from obj_to_free_list */
fill_pool_from_freelist();
if (likely(READ_ONCE(obj_pool_free) >= debug_objects_pool_min_level))
return;
/*
* On RT enabled kernels the pool refill must happen in preemptible
* context -- for !RT kernels we rely on the fact that spinlock_t and