kernel-packages team mailing list archive

[Rodrigo Vaz <1391339@xxxxxxxxxxxxxxxxxx>]

Hi Kamal, thanks for puting together a PPA with the test kernel but
unfortunately I had the same results:

Linux runtime-common 4 3.13.0-40-generic #68+g73d3fe6-Ubuntu SMP Tue Nov
11 16:39:20 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

GRO enabled:
root@runtime-common.23 ~# for i in {1..3}; do ab -n 10 $URL | grep "Transfer rate"; done
Transfer rate:          47312.68 [Kbytes/sec] received
Transfer rate:          82794.75 [Kbytes/sec] received
Transfer rate:          68697.54 [Kbytes/sec] received

GRO disabled:
root@runtime-common.23 ~# ethtool -K eth0 gro off
root@runtime-common.23 ~# for i in {1..3}; do ab -n 10 $URL | grep "Transfer rate"; done
Transfer rate:          81509.55 [Kbytes/sec] received
Transfer rate:          82609.47 [Kbytes/sec] received
Transfer rate:          90442.16 [Kbytes/sec] received


Regards,
Rodrigo.

-- 
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