net: avoid one atomic operation in skb_clone()
Fast clone cloning can actually avoid an atomic_inc(), if we guarantee prior clone_ref value is 1. This requires a change kfree_skbmem(), to perform the atomic_dec_and_test() on clone_ref before setting fclone to SKB_FCLONE_UNAVAILABLE. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
parent
e500f488c2
commit
ce1a4ea3f1
1 changed files with 17 additions and 6 deletions
|
@ -541,13 +541,20 @@ static void kfree_skbmem(struct sk_buff *skb)
|
|||
case SKB_FCLONE_CLONE:
|
||||
fclones = container_of(skb, struct sk_buff_fclones, skb2);
|
||||
|
||||
/* The clone portion is available for
|
||||
* fast-cloning again.
|
||||
/* Warning : We must perform the atomic_dec_and_test() before
|
||||
* setting skb->fclone back to SKB_FCLONE_UNAVAILABLE, otherwise
|
||||
* skb_clone() could set clone_ref to 2 before our decrement.
|
||||
* Anyway, if we are going to free the structure, no need to
|
||||
* rewrite skb->fclone.
|
||||
*/
|
||||
skb->fclone = SKB_FCLONE_UNAVAILABLE;
|
||||
|
||||
if (atomic_dec_and_test(&fclones->fclone_ref))
|
||||
if (atomic_dec_and_test(&fclones->fclone_ref)) {
|
||||
kmem_cache_free(skbuff_fclone_cache, fclones);
|
||||
} else {
|
||||
/* The clone portion is available for
|
||||
* fast-cloning again.
|
||||
*/
|
||||
skb->fclone = SKB_FCLONE_UNAVAILABLE;
|
||||
}
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
@ -869,7 +876,11 @@ struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
|
|||
if (skb->fclone == SKB_FCLONE_ORIG &&
|
||||
n->fclone == SKB_FCLONE_UNAVAILABLE) {
|
||||
n->fclone = SKB_FCLONE_CLONE;
|
||||
atomic_inc(&fclones->fclone_ref);
|
||||
/* As our fastclone was free, clone_ref must be 1 at this point.
|
||||
* We could use atomic_inc() here, but it is faster
|
||||
* to set the final value.
|
||||
*/
|
||||
atomic_set(&fclones->fclone_ref, 2);
|
||||
} else {
|
||||
if (skb_pfmemalloc(skb))
|
||||
gfp_mask |= __GFP_MEMALLOC;
|
||||
|
|
Loading…
Reference in a new issue