diff options
author | Waiman Long <longman@redhat.com> | 2017-01-05 15:17:05 -0500 |
---|---|---|
committer | Thomas Gleixner <tglx@linutronix.de> | 2017-02-05 17:09:32 +0100 |
commit | 858274b6a13b4db0e6fb451eea7f8817c42426a7 (patch) | |
tree | e5c48673426a0569dee43279bca4d499ce80e9ae /lib/debugobjects.c | |
parent | 97dd552eb23c83dbf626a6e84666c7e281375d47 (diff) |
debugobjects: Reduce contention on the global pool_lock
On a large SMP system with many CPUs, the global pool_lock may become
a performance bottleneck as all the CPUs that need to allocate or
free debug objects have to take the lock. That can sometimes cause
soft lockups like:
NMI watchdog: BUG: soft lockup - CPU#35 stuck for 22s! [rcuos/1:21]
...
RIP: 0010:[<ffffffff817c216b>] [<ffffffff817c216b>]
_raw_spin_unlock_irqrestore+0x3b/0x60
...
Call Trace:
[<ffffffff813f40d1>] free_object+0x81/0xb0
[<ffffffff813f4f33>] debug_check_no_obj_freed+0x193/0x220
[<ffffffff81101a59>] ? trace_hardirqs_on_caller+0xf9/0x1c0
[<ffffffff81284996>] ? file_free_rcu+0x36/0x60
[<ffffffff81251712>] kmem_cache_free+0xd2/0x380
[<ffffffff81284960>] ? fput+0x90/0x90
[<ffffffff81284996>] file_free_rcu+0x36/0x60
[<ffffffff81124c23>] rcu_nocb_kthread+0x1b3/0x550
[<ffffffff81124b71>] ? rcu_nocb_kthread+0x101/0x550
[<ffffffff81124a70>] ? sync_exp_work_done.constprop.63+0x50/0x50
[<ffffffff810c59d1>] kthread+0x101/0x120
[<ffffffff81101a59>] ? trace_hardirqs_on_caller+0xf9/0x1c0
[<ffffffff817c2d32>] ret_from_fork+0x22/0x50
To reduce the amount of contention on the pool_lock, the actual
kmem_cache_free() of the debug objects will be delayed if the pool_lock
is busy. This will temporarily increase the amount of free objects
available at the free pool when the system is busy. As a result,
the number of kmem_cache allocation and freeing is reduced.
To further reduce the lock operations free debug objects in batches of
four.
Signed-off-by: Waiman Long <longman@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: "Du Changbin" <changbin.du@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jan Stancek <jstancek@redhat.com>
Link: http://lkml.kernel.org/r/1483647425-4135-4-git-send-email-longman@redhat.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'lib/debugobjects.c')
-rw-r--r-- | lib/debugobjects.c | 32 |
1 files changed, 23 insertions, 9 deletions
diff --git a/lib/debugobjects.c b/lib/debugobjects.c index dc78217b2199..5e1bf2f4a5ec 100644 --- a/lib/debugobjects.c +++ b/lib/debugobjects.c @@ -172,25 +172,39 @@ alloc_object(void *addr, struct debug_bucket *b, struct debug_obj_descr *descr) /* * workqueue function to free objects. + * + * To reduce contention on the global pool_lock, the actual freeing of + * debug objects will be delayed if the pool_lock is busy. We also free + * the objects in a batch of 4 for each lock/unlock cycle. */ +#define ODEBUG_FREE_BATCH 4 + static void free_obj_work(struct work_struct *work) { - struct debug_obj *obj; + struct debug_obj *objs[ODEBUG_FREE_BATCH]; unsigned long flags; + int i; - raw_spin_lock_irqsave(&pool_lock, flags); - while (obj_pool_free > debug_objects_pool_size) { - obj = hlist_entry(obj_pool.first, typeof(*obj), node); - hlist_del(&obj->node); - obj_pool_free--; - debug_objects_freed++; + if (!raw_spin_trylock_irqsave(&pool_lock, flags)) + return; + while (obj_pool_free >= debug_objects_pool_size + ODEBUG_FREE_BATCH) { + for (i = 0; i < ODEBUG_FREE_BATCH; i++) { + objs[i] = hlist_entry(obj_pool.first, + typeof(*objs[0]), node); + hlist_del(&objs[i]->node); + } + + obj_pool_free -= ODEBUG_FREE_BATCH; + debug_objects_freed += ODEBUG_FREE_BATCH; /* * We release pool_lock across kmem_cache_free() to * avoid contention on pool_lock. */ raw_spin_unlock_irqrestore(&pool_lock, flags); - kmem_cache_free(obj_cache, obj); - raw_spin_lock_irqsave(&pool_lock, flags); + for (i = 0; i < ODEBUG_FREE_BATCH; i++) + kmem_cache_free(obj_cache, objs[i]); + if (!raw_spin_trylock_irqsave(&pool_lock, flags)) + return; } raw_spin_unlock_irqrestore(&pool_lock, flags); } |