diff options
author | Eric Dumazet <edumazet@google.com> | 2018-10-10 12:30:05 -0700 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-02-08 11:25:32 +0100 |
commit | 826ff799146685450f84e3158ce66499c928c8ea (patch) | |
tree | eafe402da8eea8a11c98ed9959c3e19206b5f0b7 | |
parent | 29ff723c549906a5d8d64dd406d1b1b4da0eb85b (diff) |
inet: frags: get rid of ipfrag_skb_cb/FRAG_CB
commit bf66337140c64c27fa37222b7abca7e49d63fb57 upstream.
ip_defrag uses skb->cb[] to store the fragment offset, and unfortunately
this integer is currently in a different cache line than skb->next,
meaning that we use two cache lines per skb when finding the insertion point.
By aliasing skb->ip_defrag_offset and skb->dev, we pack all the fields
in a single cache line and save precious memory bandwidth.
Note that after the fast path added by Changli Gao in commit
d6bebca92c66 ("fragment: add fast path for in-order fragments")
this change wont help the fast path, since we still need
to access prev->len (2nd cache line), but will show great
benefits when slow path is entered, since we perform
a linear scan of a potentially long list.
Also, note that this potential long list is an attack vector,
we might consider also using an rb-tree there eventually.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r-- | include/linux/skbuff.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 6d39d81d3c38..053bdfb526f7 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -558,6 +558,11 @@ struct sk_buff { }; struct rb_node rbnode; /* used in netem & tcp stack */ }; + + union { + int ip_defrag_offset; + }; + struct sock *sk; struct net_device *dev; |