path: root/net/phonet/datagram.c
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authorDavid S. Miller <davem@davemloft.net>2014-11-05 16:34:47 -0500
committerDavid S. Miller <davem@davemloft.net>2014-11-05 16:34:47 -0500
commit1d76c1d028975df8488d1ae18a76f268eb5efa93 (patch)
tree01bfc4d3ef16fe7e5a4da0be1e7f3fd432e7495f /net/phonet/datagram.c
parentMerge branch 'stmmac-next' (diff)
parentgue: Receive side of remote checksum offload (diff)
Merge branch 'gue-next'
Tom Herbert says: ==================== gue: Remote checksum offload This patch set implements remote checksum offload for GUE, which is a mechanism that provides checksum offload of encapsulated packets using rudimentary offload capabilities found in most Network Interface Card (NIC) devices. The outer header checksum for UDP is enabled in packets and, with some additional meta information in the GUE header, a receiver is able to deduce the checksum to be set for an inner encapsulated packet. Effectively this offloads the computation of the inner checksum. Enabling the outer checksum in encapsulation has the additional advantage that it covers more of the packet than the inner checksum including the encapsulation headers. Remote checksum offload is described in: http://tools.ietf.org/html/draft-herbert-remotecsumoffload-01 The GUE transmit and receive paths are modified to support the remote checksum offload option. The option contains a checksum offset and checksum start which are directly derived from values set in stack when doing CHECKSUM_PARTIAL. On receipt of the option, the operation is to calculate the packet checksum from "start" to end of the packet (normally derived for checksum complete), and then set the resultant value at checksum "offset" (the checksum field has already been primed with the pseudo header). This emulates a NIC that implements NETIF_F_HW_CSUM. The primary purpose of this feature is to eliminate cost of performing checksum calculation over a packet when encpasulating. In this patch set: - Move fou_build_header into fou.c and split it into a couple of functions - Enable offloading of outer UDP checksum in encapsulation - Change udp_offload to support remote checksum offload, includes new GSO type and ensuring encapsulated layers (TCP) doesn't try to set a checksum covered by RCO - TX support for RCO with GUE. This is configured through ip_tunnel and set the option on transmit when packet being encapsulated is CHECKSUM_PARTIAL - RX support for RCO with GUE for normal and GRO paths. Includes resolving the offloaded checksum v2: Address comments from davem: Move accounting for private option field in gue_encap_hlen to patch in which we add the remote checksum offload option. Testing: I ran performance numbers using netperf TCP_STREAM and TCP_RR with 200 streams, comparing GUE with and without remote checksum offload (doing checksum-unnecessary to complete conversion in both cases). These were run on mlnx4 and bnx2x. Some mlnx4 results are below. GRE/GUE TCP_STREAM IPv4, with remote checksum offload 9.71% TX CPU utilization 7.42% RX CPU utilization 36380 Mbps IPv4, without remote checksum offload 12.40% TX CPU utilization 7.36% RX CPU utilization 36591 Mbps TCP_RR IPv4, with remote checksum offload 77.79% CPU utilization 91/144/216 90/95/99% latencies 1.95127e+06 tps IPv4, without remote checksum offload 78.70% CPU utilization 89/152/297 90/95/99% latencies 1.95458e+06 tps IPIP/GUE TCP_STREAM With remote checksum offload 10.30% TX CPU utilization 7.43% RX CPU utilization 36486 Mbps Without remote checksum offload 12.47% TX CPU utilization 7.49% RX CPU utilization 36694 Mbps TCP_RR With remote checksum offload 77.80% CPU utilization 87/153/270 90/95/99% latencies 1.98735e+06 tps Without remote checksum offload 77.98% CPU utilization 87/150/287 90/95/99% latencies 1.98737e+06 tps SIT/GUE TCP_STREAM With remote checksum offload 9.68% TX CPU utilization 7.36% RX CPU utilization 35971 Mbps Without remote checksum offload 12.95% TX CPU utilization 8.04% RX CPU utilization 36177 Mbps TCP_RR With remote checksum offload 79.32% CPU utilization 94/158/295 90/95/99% latencies 1.88842e+06 tps Without remote checksum offload 80.23% CPU utilization 94/149/226 90/95/99% latencies 1.90338e+06 tps VXLAN TCP_STREAM 35.03% TX CPU utilization 20.85% RX CPU utilization 36230 Mbps TCP_RR 77.36% CPU utilization 84/146/270 90/95/99% latencies 2.08063e+06 tps We can also look at CPU time in csum_partial using perf (with bnx2x setup). For GRE with TCP_STREAM I see: With remote checksum offload 0.33% TX 1.81% RX Without remote checksum offload 6.00% TX 0.51% RX I suspect the fact that time in csum_partial noticably increases with remote checksum offload for RX is due to taking the cache miss on the encapsulated header in that function. By similar reasoning, if on the TX side the packet were not in cache (say we did a splice from a file whose data was never touched by the CPU) the CPU savings for TX would probably be more pronounced. ==================== Signed-off-by: David S. Miller <davem@davemloft.net>
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