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| author | Eric Dumazet | 2018-03-31 21:58:58 +0200 |
|---|---|---|
| committer | David S. Miller | 2018-04-01 05:25:40 +0200 |
| commit | bf66337140c64c27fa37222b7abca7e49d63fb57 (patch) | |
| tree | 21a458948982fa21406bf356534516789d435661 /include/linux/skbuff.h | |
| parent | inet: frags: reorganize struct netns_frags (diff) | |
| download | kernel-qcow2-linux-bf66337140c64c27fa37222b7abca7e49d63fb57.tar.gz kernel-qcow2-linux-bf66337140c64c27fa37222b7abca7e49d63fb57.tar.xz kernel-qcow2-linux-bf66337140c64c27fa37222b7abca7e49d63fb57.zip | |
inet: frags: get rid of ipfrag_skb_cb/FRAG_CB
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>
Diffstat (limited to 'include/linux/skbuff.h')
| -rw-r--r-- | include/linux/skbuff.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 47082f54ec1f..9065477ed255 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -672,6 +672,7 @@ struct sk_buff { * UDP receive path is one user. */ unsigned long dev_scratch; + int ip_defrag_offset; }; }; struct rb_node rbnode; /* used in netem & tcp stack */ |