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[PATCH] Use 32 bit division in slab_put_obj() 

Improve the performance of slab_put_obj().  Without the cast, gcc considers
ptrdiff_t a 64 bit signed integer and ends up emitting code to use a full
signed 128 bit divide on EM64T, which is substantially slower than a 32 bit
unsigned divide.

I noticed this when looking at the profile of a case where the slab balance
is just on edge and thrashes back and forth freeing a block.

Signed-off-by: Benjamin LaHaise <benjamin.c.lahaise@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Benjamin LaHaise 2006-02-01 03:05:30 -08:00 committed by Linus Torvalds
parent c84db23c6e
commit 9884fd8df1
1 changed files with 3 additions and 3 deletions
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6
mm/slab.c
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@ -1398,7 +1398,7 @@ static void check_poison_obj(kmem_cache_t *cachep, void *objp)
struct slab *slabp = page_get_slab(virt_to_page(objp));
int objnr;
objnr = (objp - slabp->s_mem) / cachep->objsize;
objnr = (unsigned)(objp - slabp->s_mem) / cachep->objsize;
if (objnr) {
objp = slabp->s_mem + (objnr - 1) * cachep->objsize;
realobj = (char *)objp + obj_dbghead(cachep);
@ -2341,7 +2341,7 @@ static void *cache_free_debugcheck(kmem_cache_t *cachep, void *objp,
if (cachep->flags & SLAB_STORE_USER)
*dbg_userword(cachep, objp) = caller;
objnr = (objp - slabp->s_mem) / cachep->objsize;
objnr = (unsigned)(objp - slabp->s_mem) / cachep->objsize;
BUG_ON(objnr >= cachep->num);
BUG_ON(objp != slabp->s_mem + objnr * cachep->objsize);
@ -2699,7 +2699,7 @@ static void free_block(kmem_cache_t *cachep, void **objpp, int nr_objects,
slabp = page_get_slab(virt_to_page(objp));
l3 = cachep->nodelists[node];
list_del(&slabp->list);
objnr = (objp - slabp->s_mem) / cachep->objsize;
objnr = (unsigned)(objp - slabp->s_mem) / cachep->objsize;
check_spinlock_acquired_node(cachep, node);
check_slabp(cachep, slabp);