On Wed, 30 Sep 2015 13:44:19 +0200 Jesper Dangaard Brouer <bro...@redhat.com>
wrote:
> Make it possible to free a freelist with several objects by adjusting
> API of slab_free() and __slab_free() to have head, tail and an objects
> counter (cnt).
>
> Tail being NULL indicate single object free of head object. This
> allow compiler inline constant propagation in slab_free() and
> slab_free_freelist_hook() to avoid adding any overhead in case of
> single object free.
>
> This allows a freelist with several objects (all within the same
> slab-page) to be free'ed using a single locked cmpxchg_double in
> __slab_free() and with an unlocked cmpxchg_double in slab_free().
>
> Object debugging on the free path is also extended to handle these
> freelists. When CONFIG_SLUB_DEBUG is enabled it will also detect if
> objects don't belong to the same slab-page.
>
> These changes are needed for the next patch to bulk free the detached
> freelists it introduces and constructs.
>
> Micro benchmarking showed no performance reduction due to this change,
> when debugging is turned off (compiled with CONFIG_SLUB_DEBUG).
>
checkpatch says
WARNING: Avoid crashing the kernel - try using WARN_ON & recovery code rather
than BUG() or BUG_ON()
#205: FILE: mm/slub.c:2888:
+ BUG_ON(!size);
Linus will get mad at you if he finds out, and we wouldn't want that.
--- a/mm/slub.c~slub-optimize-bulk-slowpath-free-by-detached-freelist-fix
+++ a/mm/slub.c
@@ -2885,7 +2885,8 @@ static int build_detached_freelist(struc
/* Note that interrupts must be enabled when calling this function. */
void kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p)
{
- BUG_ON(!size);
+ if (WARN_ON(!size))
+ return;
do {
struct detached_freelist df;
_
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