From: Christoph Lameter <cl@linux.com>
To: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: David Rientjes <rientjes@google.com>,
linux-mm@kvack.org, Eric Dumazet <eric.dumazet@gmail.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: [slubll1 16/19] slub: Avoid disabling interrupts in free slowpath
Date: Wed, 30 Mar 2011 15:23:58 -0500 [thread overview]
Message-ID: <20110330202425.248941090@linux.com> (raw)
In-Reply-To: 20110330202342.669400887@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 2011-03-30 14:43:44.000000000 -0500
+++ linux-2.6/mm/slub.c 2011-03-30 14:43:51.000000000 -0500
@@ -2209,13 +2209,11 @@ 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;
@@ -2234,7 +2232,11 @@ 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;
@@ -2250,7 +2252,7 @@ static void __slab_free(struct kmem_cach
*/
if (was_frozen)
stat(s, FREE_FROZEN);
- goto out_unlock;
+ return;
}
/*
@@ -2273,12 +2275,10 @@ 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;
@@ -2291,9 +2291,10 @@ 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:[~2011-03-30 20:24 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-30 20:23 [slubll1 00/19] SLUB: Implement mostly lockless slowpaths Christoph Lameter
2011-03-30 20:23 ` [slubll1 01/19] percpu: Fixup __this_cpu_xchg* operations Christoph Lameter
2011-03-30 20:23 ` [slubll1 02/19] slub: get_map() function to establish map of free objects in a slab Christoph Lameter
2011-03-30 20:23 ` [slubll1 03/19] slub: Eliminate repeated use of c->page through a new page variable Christoph Lameter
2011-03-30 20:23 ` [slubll1 04/19] slub: Move node determination out of hotpath Christoph Lameter
2011-03-30 20:23 ` [slubll1 05/19] slub: Move debug handlign in __slab_free Christoph Lameter
2011-03-30 20:23 ` [slubll1 06/19] slub: Do not use frozen page flag but a bit in the page counters Christoph Lameter
2011-03-30 20:23 ` [slubll1 07/19] slub: Move page->frozen handling near where the page->freelist handling occurs Christoph Lameter
2011-03-30 20:23 ` [slubll1 08/19] x86: Add support for cmpxchg_double Christoph Lameter
2011-03-30 20:23 ` [slubll1 09/19] mm: Rearrange struct page Christoph Lameter
2011-03-30 20:23 ` [slubll1 10/19] slub: Add cmpxchg_double_slab() Christoph Lameter
2011-03-30 20:23 ` [slubll1 11/19] slub: explicit list_lock taking Christoph Lameter
2011-03-30 20:23 ` [slubll1 12/19] slub: Pass kmem_cache struct to lock and freeze slab Christoph Lameter
2011-03-30 20:23 ` [slubll1 13/19] slub: Rework allocator fastpaths Christoph Lameter
2011-03-30 20:23 ` [slubll1 14/19] slub: Invert locking and avoid slab lock Christoph Lameter
2011-03-30 20:23 ` [slubll1 15/19] slub: Disable interrupts in free_debug processing Christoph Lameter
2011-03-30 20:23 ` Christoph Lameter [this message]
2011-03-30 20:23 ` [slubll1 17/19] slub: Get rid of the another_slab label Christoph Lameter
2011-03-30 20:24 ` [slubll1 18/19] slub: fast release on full slab Christoph Lameter
2011-03-30 20:24 ` [slubll1 19/19] slub: Not necessary to check for empty slab on load_freelist Christoph Lameter
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