On Fri, Nov 20, 2015 at 01:21:58PM -0800, Tom Herbert wrote:
> +
> + while (eaten < orig_len) {
> + /* Always clone since we will consume something */
> + skb = skb_clone(orig_skb, GFP_ATOMIC);
> + if (!skb) {
> + desc->error = -ENOMEM;
> + break;
> + }
...
> + if (!pskb_pull(skb, offset + eaten)) {
pskb_pull after clone == pskb_expand_head
meaning that we'll be linearizing things all the time.
can we try skb_share_check() first ?
the packet shouldn't be shared at this point, so it might save a lot.
> + kfree_skb(skb);
> + desc->error = -ENOMEM;
> + break;
> + }
...
> + /* Need to trim, should be rare? */
> + err = pskb_trim(skb, orig_len - eaten);
...
> + if (!rxm->full_len) {
> + ssize_t len;
> +
> + len = KCM_RUN_FILTER(psock->bpf_prog, head);
bpf can read packet beyond linear header just fine.
It's slower than reads from header, since extra calls invovled,
but if that becomes a bottle neck we can optimize the way we do JIT there.
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