On 03/25/2019 02:14 AM, Felix Fietkau wrote:
> Since we're freeing multiple skbs, we might as well use bulk free to save a
> few cycles. Use the same conditions for bulk free as in napi_consume_skb.
>
> Signed-off-by: Felix Fietkau <n...@nbd.name>
> ---
> v3: reorder checks to prevent skb double unref
> v2: call kmem_cache_free_bulk once the skb array is full instead of
> falling back to kfree_skb
> net/core/skbuff.c | 40 ++++++++++++++++++++++++++++++++++++----
> 1 file changed, 36 insertions(+), 4 deletions(-)
>
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 2415d9cb9b89..ca0308485669 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -666,12 +666,44 @@ EXPORT_SYMBOL(kfree_skb);
>
> void kfree_skb_list(struct sk_buff *segs)
> {
> - while (segs) {
> - struct sk_buff *next = segs->next;
> + struct sk_buff *next = segs;
> + void *skbs[16];
> + int n_skbs = 0;
>
> - kfree_skb(segs);
> - segs = next;
> + while ((segs = next) != NULL) {
> + next = segs->next;
> +
> + if (segs->fclone != SKB_FCLONE_UNAVAILABLE) {
> + kfree_skb(segs);
> + continue;
> + }
> +
> + if (!skb_unref(segs))
> + continue;
> +
> + trace_kfree_skb(segs, __builtin_return_address(0));
> +
> + /* drop skb->head and call any destructors for packet */
> + skb_release_all(segs);
> +
> +#ifdef CONFIG_SLUB
> + /* SLUB writes into objects when freeing */
> + prefetchw(segs);
> +#endif
This is done too late :
You should probably either remove this prefetchw()
or do it before reading segs->next at the beginning of the loop.
> +
> + skbs[n_skbs++] = segs;
> +
> + if (n_skbs < ARRAY_SIZE(skbs))
> + continue;
> +
> + kmem_cache_free_bulk(skbuff_head_cache, n_skbs, skbs);
> + n_skbs = 0;
> }
> +
> + if (!n_skbs)
> + return;
> +
> + kmem_cache_free_bulk(skbuff_head_cache, n_skbs, skbs);
> }
> EXPORT_SYMBOL(kfree_skb_list);
>
>
