From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 2840390008C for ; Fri, 15 Apr 2011 16:13:07 -0400 (EDT) Message-Id: <20110415201304.808185101@linux.com> Date: Fri, 15 Apr 2011 15:13:03 -0500 From: Christoph Lameter Subject: [slubllv333num@/21] slub: Avoid disabling interrupts in free slowpath References: <20110415201246.096634892@linux.com> Content-Disposition: inline; filename=slab_free_without_irqoff Sender: owner-linux-mm@kvack.org List-ID: To: Pekka Enberg Cc: David Rientjes , Hugh Dickins , Eric Dumazet , "H. Peter Anvin" , Mathieu Desnoyers , linux-mm@kvack.org Disabling interrupts can be avoided now. However, list operation still require disabling interrupts since allocations can occur from interrupt contexts and there is no way to perform atomic list operations. So acquire the list lock opportunistically if there is a chance that list operations would be needed. This may result in needless synchronizations but allows the avoidance of synchronization in the majority of the cases. Dropping interrupt handling significantly simplifies the slowpath. Signed-off-by: Christoph Lameter --- mm/slub.c | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-) Index: linux-2.6/mm/slub.c =================================================================== --- linux-2.6.orig/mm/slub.c 2011-04-15 14:30:05.000000000 -0500 +++ linux-2.6/mm/slub.c 2011-04-15 14:30:06.000000000 -0500 @@ -2225,13 +2225,11 @@ static void __slab_free(struct kmem_cach struct kmem_cache_node *n = NULL; #ifdef CONFIG_CMPXCHG_LOCAL unsigned long flags; - - local_irq_save(flags); #endif stat(s, FREE_SLOWPATH); if (kmem_cache_debug(s) && !free_debug_processing(s, page, x, addr)) - goto out_unlock; + return; do { prior = page->freelist; @@ -2250,7 +2248,11 @@ static void __slab_free(struct kmem_cach * Otherwise the list_lock will synchronize with * other processors updating the list of slabs. */ +#ifdef CONFIG_CMPXCHG_LOCAL + spin_lock_irqsave(&n->list_lock, flags); +#else spin_lock(&n->list_lock); +#endif } inuse = new.inuse; @@ -2266,7 +2268,7 @@ static void __slab_free(struct kmem_cach */ if (was_frozen) stat(s, FREE_FROZEN); - goto out_unlock; + return; } /* @@ -2289,12 +2291,10 @@ static void __slab_free(struct kmem_cach stat(s, FREE_ADD_PARTIAL); } } - - spin_unlock(&n->list_lock); - -out_unlock: #ifdef CONFIG_CMPXCHG_LOCAL - local_irq_restore(flags); + spin_unlock_irqrestore(&n->list_lock, flags); +#else + spin_unlock(&n->list_lock); #endif return; @@ -2307,9 +2307,10 @@ slab_empty: stat(s, FREE_REMOVE_PARTIAL); } - spin_unlock(&n->list_lock); #ifdef CONFIG_CMPXCHG_LOCAL - local_irq_restore(flags); + spin_unlock_irqrestore(&n->list_lock, flags); +#else + spin_unlock(&n->list_lock); #endif stat(s, FREE_SLAB); discard_slab(s, page); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org