** Changed in: linux (Ubuntu Bionic)
Status: Fix Released => Fix Committed
** Description changed:
Hardware:
HP DL380 Gen 7 server with Gigabit interface.
Ubuntu release: 18.04.1
Since upgrading from 4.15.0-33 to 4.15.0-36, I have noticed a dramatic
slowdown in TCP over IPv6.
Set up: two servers, Server A in US on Ubuntu 18.04.1, Server B in
Europe.
Test: Sending 400MB over TCP from Server B to Server A.
With 4.15.0-33 on Server A, the transfer is completed in 24 seconds,
with average speed of 139 mbps.
With 4.15.0-36 on Server A, the same amount of data is transferred in
369 seconds, average speed less than 9 mbps.
Looking at the result from tcpdump, I see that the there is a big
difference in the TCP Window size.
- With 3.15-0.33 the TCP window size is around 30000. But with 3.15-0.36,
+ With 4.15-0.33 the TCP window size is around 30000. But with 4.15-0.36,
the window size is only 734.
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https://bugs.launchpad.net/bugs/1796895
Title:
Kernel 4.15.0-36 network performance regression
Status in linux package in Ubuntu:
Fix Released
Status in linux source package in Bionic:
Fix Committed
Bug description:
Hardware:
HP DL380 Gen 7 server with Gigabit interface.
Ubuntu release: 18.04.1
Since upgrading from 4.15.0-33 to 4.15.0-36, I have noticed a dramatic
slowdown in TCP over IPv6.
Set up: two servers, Server A in US on Ubuntu 18.04.1, Server B in
Europe.
Test: Sending 400MB over TCP from Server B to Server A.
With 4.15.0-33 on Server A, the transfer is completed in 24 seconds,
with average speed of 139 mbps.
With 4.15.0-36 on Server A, the same amount of data is transferred in
369 seconds, average speed less than 9 mbps.
Looking at the result from tcpdump, I see that the there is a big
difference in the TCP Window size.
With 4.15-0.33 the TCP window size is around 30000. But with
4.15-0.36, the window size is only 734.
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1796895/+subscriptions
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