On Fri, Nov 20, 2015 at 3:10 PM, Alexei Starovoitov
<alexei.starovoi...@gmail.com> wrote:
> 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.
>
Yes it might. This pull does seem to be expensive.
>> + 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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