From: Alexander Duyck <adu...@mirantis.com> Date: Fri, 05 Feb 2016 15:27:25 -0800
> This patch series updates the existing segmentation offload code for > tunnels to make better use of existing and updated GSO checksum > computation. This is done primarily through two mechanisms. First we > maintain a separate checksum in the GSO context block of the sk_buff. This > allows us to maintain two checksum values, one offloaded with values stored > in csum_start and csum_offset, and one computed and tracked in > SKB_GSO_CB(skb)->csum. By maintaining these two values we are able to take > advantage of the same sort of math used in local checksum offload so that > we can provide both inner and outer checksums with minimal overhead. > > Below is the performance for a netperf session between an ixgbe PF and VF > on the same host but in different namespaces. As can be seen a significant > gain in performance can be had from allowing the use of Tx checksum offload > on the inner headers while performing a software offload on the outer > header computation: > > Recv Send Send Utilization Service Demand > Socket Socket Message Elapsed Send Recv Send Recv > Size Size Size Time Throughput local remote local remote > bytes bytes bytes secs. 10^6bits/s % S % U us/KB us/KB > > Before: > 87380 16384 16384 10.00 12844.38 9.30 -1.00 0.712 -1.00 > After: > 87380 16384 16384 10.00 13216.63 6.78 -1.00 0.504 -1.000 > > Changes from v1: > * Dropped use of CHECKSUM_UNNECESSARY for remote checksum offload > * Left encap_hdr_csum as it will likely be needed in future for SCTP GSO > * Broke the changes out over many more patches > * Updated GRE segmentation to more closely match UDP tunnel segmentation Series applied, thanks Alex.
