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author | Eric Dumazet <edumazet@google.com> | 2013-01-10 12:36:42 +0000 |
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committer | David S. Miller <davem@davemloft.net> | 2013-01-10 14:58:13 -0800 |
commit | 1def9238d4aa2146924994aa4b7dc861f03b9362 (patch) | |
tree | 8b529029fae8f8a4575b088dbe76e8b84a1c9ccd /kernel | |
parent | 3d55b323709661df34d93e4cdcc5337620e34dfd (diff) | |
download | linux-1def9238d4aa2146924994aa4b7dc861f03b9362.tar.bz2 |
net_sched: more precise pkt_len computation
One long standing problem with TSO/GSO/GRO packets is that skb->len
doesn't represent a precise amount of bytes on wire.
Headers are only accounted for the first segment.
For TCP, thats typically 66 bytes per 1448 bytes segment missing,
an error of 4.5 % for normal MSS value.
As consequences :
1) TBF/CBQ/HTB/NETEM/... can send more bytes than the assigned limits.
2) Device stats are slightly under estimated as well.
Fix this by taking account of headers in qdisc_skb_cb(skb)->pkt_len
computation.
Packet schedulers should use qdisc pkt_len instead of skb->len for their
bandwidth limitations, and TSO enabled devices drivers could use pkt_len
if their statistics are not hardware assisted, and if they don't scratch
skb->cb[] first word.
Both egress and ingress paths work, thanks to commit fda55eca5a
(net: introduce skb_transport_header_was_set()) : If GRO built
a GSO packet, it also set the transport header for us.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Paolo Valente <paolo.valente@unimore.it>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel')
0 files changed, 0 insertions, 0 deletions