From: Christoph Lameter <cl@linux.com>
To: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: David Rientjes <rientjes@google.com>,
Hugh Dickins <hughd@google.com>,
Eric Dumazet <eric.dumazet@gmail.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
linux-mm@kvack.org
Subject: [slubllv333num@/21] slub: Avoid disabling interrupts in free slowpath
Date: Fri, 15 Apr 2011 15:13:03 -0500 [thread overview]
Message-ID: <20110415201304.808185101@linux.com> (raw)
In-Reply-To: 20110415201246.096634892@linux.com
[-- Attachment #1: slab_free_without_irqoff --]
[-- Type: text/plain, Size: 2731 bytes --]
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 <cl@linux.com>
---
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);
--
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next prev parent reply other threads:[~2011-04-15 20:13 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-15 20:12 [slubllv333num@/21] SLUB: Lockless freelists for objects V3 Christoph Lameter
2011-04-15 20:12 ` [slubllv333num@/21] slub: Use NUMA_NO_NODE in get_partial Christoph Lameter
2011-04-15 20:12 ` [slubllv333num@/21] slub: get_map() function to establish map of free objects in a slab Christoph Lameter
2011-04-15 20:12 ` [slubllv333num@/21] slub: Eliminate repeated use of c->page through a new page variable Christoph Lameter
2011-04-15 20:12 ` [slubllv333num@/21] slub: Move node determination out of hotpath Christoph Lameter
2011-04-15 20:12 ` [slubllv333num@/21] slub: Move debug handlign in __slab_free Christoph Lameter
2011-04-15 20:12 ` [slubllv333num@/21] slub: Per object NUMA support Christoph Lameter
2011-04-15 20:12 ` [slubllv333num@/21] slub: Do not use frozen page flag but a bit in the page counters Christoph Lameter
2011-04-15 20:12 ` [slubllv333num@/21] slub: Move page->frozen handling near where the page->freelist handling occurs Christoph Lameter
2011-04-15 20:12 ` [slubllv333num@/21] x86: Add support for cmpxchg_double Christoph Lameter
2011-04-15 20:12 ` [slubllv333num@/21] mm: Rearrange struct page Christoph Lameter
2011-04-15 20:12 ` [slubllv333num@/21] slub: Add cmpxchg_double_slab() Christoph Lameter
2011-04-15 20:12 ` [slubllv333num@/21] slub: explicit list_lock taking Christoph Lameter
2011-04-15 20:12 ` [slubllv333num@/21] slub: Pass kmem_cache struct to lock and freeze slab Christoph Lameter
2011-04-15 20:13 ` [slubllv333num@/21] slub: Rework allocator fastpaths Christoph Lameter
2011-04-15 20:13 ` [slubllv333num@/21] slub: Invert locking and avoid slab lock Christoph Lameter
2011-04-15 20:13 ` [slubllv333num@/21] slub: Disable interrupts in free_debug processing Christoph Lameter
2011-04-15 20:13 ` Christoph Lameter [this message]
2011-04-15 20:13 ` [slubllv333num@/21] slub: Get rid of the another_slab label Christoph Lameter
2011-04-15 20:13 ` [slubllv333num@/21] slub: fast release on full slab Christoph Lameter
2011-04-15 20:13 ` [slubllv333num@/21] slub: Not necessary to check for empty slab on load_freelist Christoph Lameter
2011-04-15 20:13 ` [slubllv333num@/21] slub: update statistics for cmpxchg handling Christoph Lameter
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