This bug is missing log files that will aid in diagnosing the problem. >From a terminal window please run:
apport-collect 1344323 and then change the status of the bug to 'Confirmed'. If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'. This change has been made by an automated script, maintained by the Ubuntu Kernel Team. ** Changed in: linux (Ubuntu) Status: New => Incomplete ** Tags added: trusty -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1344323 Title: Trusty kernel network performance regression Status in “linux” package in Ubuntu: Incomplete Bug description: SRU Justification: Impact: Reduced TCP/IP receive performance for network devices that do not split packet headers into skb linear area (e.g., mlx4). The trusty kernel has incorporated commit eff44f9cc9a02aad53d568d3ae5020b6792ae4f6 Author: Jerry Chu <hk...@google.com> Date: Wed Dec 11 20:53:45 2013 -0800 net-gro: Prepare GRO stack for the upcoming tunneling support which modifies the GRO frag0 optimization, but unfortunately for some cases results in calls to __skb_pull_tail for every packet being received via the GRO path. This causes a reduction in TCP receive performance (or, more accurately, an increase in CPU load for TCP receive processing, which will cause throughput reduction for CPU limited workloads). Fix: This has already been fixed in mainline in commit a50e233c50dbc881abaa0e4070789064e8d12d70 Author: Eric Dumazet <eduma...@google.com> Date: Sat Mar 29 21:28:21 2014 -0700 net-gro: restore frag0 optimization The fix has been backported to and verified on the trusty kernel using mlx4 devices and iperf; an increase from 7.5 to 8.5 Gb/sec was observed when adding the patch, and the relevant portion of perf captures show changes in the call paths from: 7.17% iperf [kernel.kallsyms] [k] __pskb_pull_tail | --- __pskb_pull_tail | |--48.03%-- tcp_gro_receive | tcp4_gro_receive | inet_gro_receive | dev_gro_receive | napi_gro_frags | mlx4_en_process_rx_cq | mlx4_en_poll_rx_cq | net_rx_action | __do_softirq [...] |--28.53%-- napi_gro_frags | mlx4_en_process_rx_cq | mlx4_en_poll_rx_cq | net_rx_action | __do_softirq [...] |--13.11%-- inet_gro_receive | dev_gro_receive | napi_gro_frags | mlx4_en_process_rx_cq | mlx4_en_poll_rx_cq | net_rx_action | __do_softirq to: 4.87% iperf [kernel.kallsyms] [k] skb_gro_receive | --- skb_gro_receive | |--98.13%-- tcp_gro_receive | tcp4_gro_receive | inet_gro_receive | dev_gro_receive | napi_gro_frags | mlx4_en_process_rx_cq | mlx4_en_poll_rx_cq | net_rx_action | __do_softirq Testcase: The fix was tested using mlx4 10Gb/sec network devices between two arm64 systems using "iperf -s" on one end and "iperf -c" on the other. The unmodified kernel reported approximately 7.5 Gb/sec throughput, the fixed kernel approximately 8.5 Gb/sec. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1344323/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp