Hi Rodrigo, there is a possibility that the problem is not a regression in handling GRO but actually supporting GRO. I can find the following commit in 3.13-rc1:
commit 99d3d587b2b4314ccc8ea066cb327dfb523d598e Author: Wei Liu <wei.l...@citrix.com> Date: Mon Sep 30 13:46:34 2013 +0100 xen-netfront: convert to GRO API Now I tried to reproduce the performance issue locally and using a Xen-4.4.1 Trusty host which runs a Trusty PV guest. On the guest side I start iperf in server mode (since that is the receive side, but to be sure I reversed the setup with the same results) and on a desktop running Trusty, I start iperf in client mode connecting to the PV guest. The desktop and host have 1Gbit NICs. With that I get an average of about 850Mbit/sec over 10 runs. Which is as good as I would expect it. And this does not change significantly whether I enable or disable GRO. Now what we do not know is what gets involved network-wise between your server and the guests. Not really sure how this would possibly happen. -- 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/1391339 Title: Trusty kernel inbound network performance regression when GRO is enabled Status in “linux” package in Ubuntu: Confirmed Bug description: After upgrading our EC2 instances from Lucid to Trusty we noticed an increase on download times, Lucid instances were able to download twice as fast as Trusty. After some investigation and testing older kernels (precise, raring and saucy) we confirmed that this only happens on trusty kernel or newer since utopic kernel shows the same result and disabling gro with `ethtool -K eth0 gro off` seems to fix the problem making download speed the same as the Lucid instances again. The problem is easily reproducible using Apache Bench a couple times on files bigger than 100MB on 1Gb network (EC2) using HTTP or HTTPS. Following is an example of download throughput with and without gro: root@runtime-common.22 ~# ethtool -K eth0 gro off root@runtime-common.22 ~# for i in {1..10}; do ab -n 10 $URL | grep "Transfer rate"; done Transfer rate: 85183.40 [Kbytes/sec] received Transfer rate: 86375.80 [Kbytes/sec] received Transfer rate: 94720.24 [Kbytes/sec] received Transfer rate: 84783.82 [Kbytes/sec] received Transfer rate: 84933.09 [Kbytes/sec] received Transfer rate: 84714.04 [Kbytes/sec] received Transfer rate: 84795.58 [Kbytes/sec] received Transfer rate: 84636.54 [Kbytes/sec] received Transfer rate: 84924.26 [Kbytes/sec] received Transfer rate: 84994.10 [Kbytes/sec] received root@runtime-common.22 ~# ethtool -K eth0 gro on root@runtime-common.22 ~# for i in {1..10}; do ab -n 10 $URL | grep "Transfer rate"; done Transfer rate: 74193.53 [Kbytes/sec] received Transfer rate: 56808.91 [Kbytes/sec] received Transfer rate: 56011.58 [Kbytes/sec] received Transfer rate: 82227.74 [Kbytes/sec] received Transfer rate: 70806.54 [Kbytes/sec] received Transfer rate: 72848.10 [Kbytes/sec] received Transfer rate: 58451.94 [Kbytes/sec] received Transfer rate: 61221.33 [Kbytes/sec] received Transfer rate: 58620.21 [Kbytes/sec] received Transfer rate: 69950.03 [Kbytes/sec] received root@runtime-common.22 ~# Similar results can be observed using iperf and netperf as well. Tested kernels: Not affected: 3.8.0-44-generic (precise/raring), 3.11.0-26-generic (saucy) Affected: 3.13.0-39-generic (trusty), 3.16.0-24-generic (utopic) Let me know if I can provide any other information that might be helpful like perf traces and reports. Rodrigo. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1391339/+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