Christoph,
Can we revert git commit 3cdc0ed0cea50ea08dd146c1bbc82b1bcc2e1b80 ?
This is introducing a performance regression and nullifies the previous
commit.
commit 62918a036148230ba1ad175dc8a0952e3752ac57
Author: Siddha, Suresh B <[EMAIL PROTECTED]>
Date: Wed May 2 19:27:18 2007 +0200
[PATCH] x86-64: skip cache_free_alien() on non NUMA
Set use_alien_caches to 0 on non NUMA platforms. And avoid calling the
cache_free_alien() when use_alien_caches is not set. This will avoid the
cache miss that happens while dereferencing slabp to get nodeid.
Looking at the 3cdc0ed0cea50ea08dd146c1bbc82b1bcc2e1b80 changelog, I can't find
enough info of why cache_free_alien() must be called regardless if we use alien
caches or not.
Appended patch fixes the performance regression. Please comment the need
for 3cdc0ed0cea50ea08dd146c1bbc82b1bcc2e1b80, if I miss something.
thanks,
suresh
---
Skip calling cache_free_alien() when alien caches are not used.
This will avoid cache misses that happen while accessing slabp (which
is per page memory reference) to get nodeid. Instead use a global
variable to skip the call, which is mostly likely to be present in the
cache.
This gives a 0.8% performance boost with the database oltp workload
on a quad-core SMP platform and by any means the number is not small :)
Signed-off-by: Suresh Siddha <[EMAIL PROTECTED]>
---
diff --git a/mm/slab.c b/mm/slab.c
index a684778..d6e2251 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3558,7 +3558,14 @@ static inline void __cache_free(struct kmem_cache
*cachep, void *objp)
check_irq_off();
objp = cache_free_debugcheck(cachep, objp, __builtin_return_address(0));
- if (cache_free_alien(cachep, objp))
+ /*
+ * Skip calling cache_free_alien() when alien caches are not used.
+ * This will avoid cache misses that happen while accessing slabp (which
+ * is per page memory reference) to get nodeid. Instead use a global
+ * variable to skip the call, which is mostly likely to be present in
the
+ * cache.
+ */
+ if (use_alien_caches && cache_free_alien(cachep, objp))
return;
if (likely(ac->avail < ac->limit)) {
-
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