From: Toshiaki Makita Date: Mon, 27 Oct 2014 17:30:51 +0000 (-0700) Subject: net: skb_segment() should preserve backpressure X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=432c856fcf45c468fffe2e5029cb3f95c7dc9475;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git net: skb_segment() should preserve backpressure This patch generalizes commit d6a4a1041176 ("tcp: GSO should be TSQ friendly") to protocols using skb_set_owner_w() TCP uses its own destructor (tcp_wfree) and needs a more complex scheme as explained in commit 6ff50cd55545 ("tcp: gso: do not generate out of order packets") This allows UDP sockets using UFO to get proper backpressure, thus avoiding qdisc drops and excessive cpu usage. Here are performance test results (macvlan on vlan): - Before # netperf -t UDP_STREAM ... Socket Message Elapsed Messages Size Size Time Okay Errors Throughput bytes bytes secs # # 10^6bits/sec 212992 65507 60.00 144096 1224195 1258.56 212992 60.00 51 0.45 Average: CPU %user %nice %system %iowait %steal %idle Average: all 0.23 0.00 25.26 0.08 0.00 74.43 - After # netperf -t UDP_STREAM ... Socket Message Elapsed Messages Size Size Time Okay Errors Throughput bytes bytes secs # # 10^6bits/sec 212992 65507 60.00 109593 0 957.20 212992 60.00 109593 957.20 Average: CPU %user %nice %system %iowait %steal %idle Average: all 0.18 0.00 8.38 0.02 0.00 91.43 [edumazet] Rewrote patch and changelog. Signed-off-by: Toshiaki Makita Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- diff --git a/net/core/skbuff.c b/net/core/skbuff.c index c16615bfb61e..e48e5c02e877 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -3099,6 +3099,16 @@ perform_csum_check: * (see validate_xmit_skb_list() for example) */ segs->prev = tail; + + /* Following permits correct backpressure, for protocols + * using skb_set_owner_w(). + * Idea is to tranfert ownership from head_skb to last segment. + */ + if (head_skb->destructor == sock_wfree) { + swap(tail->truesize, head_skb->truesize); + swap(tail->destructor, head_skb->destructor); + swap(tail->sk, head_skb->sk); + } return segs; err: