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Message #89390
[Bug 1391339] Re: Trusty kernel inbound network performance regression when GRO is enabled
I meant, not sure how to get traffic coming in in a way that GRO
actually slows things down instead of lowering the impact of processing.
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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.
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References