On 05/29/2012 06:42 PM, Christoph Lameter wrote:
On Fri, 25 May 2012, Glauber Costa wrote:
struct page already have this information. If we start chaining
caches, this information will always be more trustworthy than
whatever is passed into the function
Yes but the lookup of the page struct also costs some cycles. SLAB in
!NUMA mode and SLOB avoid these lookups and can improve their freeing
speed because of that.
But for our case, I don't really see a way around. What I can do, is
wrap it further, so when we're not using it, code goes exactly the same
way as before, instead of always calculating the page. Would it be better?
diff --git a/mm/slub.c b/mm/slub.c
index 0eb9e72..640872f 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2598,10 +2598,14 @@ redo:
void kmem_cache_free(struct kmem_cache *s, void *x)
{
struct page *page;
+ bool slab_match;
page = virt_to_head_page(x);
- slab_free(s, page, x, _RET_IP_);
+ slab_match = (page->slab == s) | slab_is_parent(page->slab, s);
+ VM_BUG_ON(!slab_match);
Why add a slab_match bool if you do not really need it?
style. I find aux variables a very human readable way to deal with the
80-col limitation.
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