From 71086617a056a44bd6d202cb10b0ea4ceb83cfba Mon Sep 17 00:00:00 2001
From: Dmitry Fleytman <dmitry@daynix.com>
Date: Mon, 23 Dec 2013 17:38:56 +0200
Subject: [PATCH] netinet: Fix broken checksum verification in LRO mechanism
This patch applies bugfix published on FreeBSD list at Feb 2013:
http://lists.freebsd.org/pipermail/svn-src-stable-9/2013-February/003928.html
LRO mechanism is broken on systems without IP checksum verification offload.
Due to improper checksum verification RX packets omit LRO path and go
directly to TCP stack which is not good for performance.
EC2 Xen is one example of such a system.
This bug is one of the reasons we see bad performance on Amazon.
Some test results w/ and w/o the fix:
Buffer size Before After Improvement %
TCP TX
32 557.52 1386.28 149
64 552.38 1385.99 151
128 546.43 1401.46 156
256 565.25 1382.28 145
512 557.32 1375.23 147
1024 549.71 1356.69 147
2048 551.11 1371.92 149
4096 556.13 1383.67 149
8192 559.49 1364.05 144
16384 567.25 1366.48 141
32768 546.18 1366.63 150
65536 553.4 1353.87 145
TCP RX
32 107.37 105.48 -2
64 187.56 179.9 -4
128 297.16 301.71 2
256 300.47 503.92 68
512 294.76 826.13 180
1024 299.95 1916.69 539
2048 287.04 1924.44 570
4096 300.78 1929.37 541
8192 304.52 1934.02 535
16384 305.04 1957.54 542
32768 309 1921.84 522
65536 296.48 1935.41 553
Still we are pretty far from Linux, there are other problems to be fixed.
Signed-off-by: Dmitry Fleytman <dmitry@daynix.com>
Signed-off-by: Avi Kivity <avi@cloudius-systems.com>
---
bsd/sys/netinet/tcp_lro.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/bsd/sys/netinet/tcp_lro.cc b/bsd/sys/netinet/tcp_lro.cc
index 50b953715..9706b8cb1 100644
--- a/bsd/sys/netinet/tcp_lro.cc
+++ b/bsd/sys/netinet/tcp_lro.cc
@@ -335,7 +335,7 @@ tcp_lro_rx_ipv4(struct lro_ctrl *lc, struct mbuf *m, struct ip *ip4,
}
} else {
csum = in_cksum_hdr(ip4);
- if (__predict_false((csum ^ 0xffff) != 0)) {
+ if (__predict_false((csum) != 0)) {
lc->lro_bad_csum++;
return (TCP_LRO_CANNOT);
}
--
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