Messages in this thread | | | Date | Thu, 7 Jan 2016 14:47:06 -0500 | Subject | Re: [BUG] skb corruption and kernel panic at forwarding with fragmentation | From | Eric Dumazet <> |
| |
On Thu, Jan 7, 2016 at 2:35 PM, Konstantin Khlebnikov <koct9i@gmail.com> wrote: > On Thu, Jan 7, 2016 at 3:54 PM, Eric Dumazet <edumazet@google.com> wrote: want to look at git history to find out why it is done this way. >> >> TCP performance is critical for some of us, and doing such trick avoid >> one cache miss per skb in some critical list traversals. > > Right. This way tcp stuff perfectly fits into leftovers of first cache line. > Then probably it's better to put ipv4/ipv6 cb into second line from > the beginning.
Then IP forwarding might be slower.
Look, each layer (TCP , IP, ....) can organize its skb->cb[] as it wants. Nobody tries to 'make universal room' for IPCB, since only IP layer wants it.
TCP could even find a way in the future to no longer hold a copy of IPCB in the input skb, if code is reorganized a bit.
Note that skbs for output path in TCP do not need IPCB at all.
Only when skb leaves TCP and enter IP, skb->cb[] content is scratched.
| |