aws: network performance regression due to initial TCP receive buffer size change
| Affects | Status | Importance | Assigned to | Milestone | |
|---|---|---|---|---|---|
| linux-aws (Ubuntu) |
New
|
Undecided
|
Unassigned | ||
| Bionic |
Fix Released
|
High
|
Unassigned | ||
| Focal |
Fix Released
|
High
|
Unassigned | ||
| Groovy |
Fix Released
|
High
|
Unassigned | ||
Bug Description
[Impact]
AWS has seen some customers reporting networking performance degradation after they upgraded their Ubuntu instanceses. This regression is highly impacting customers who are using MTU=9000 (which is the default in EC2).
[Test case]
Bug reproduced internally in AWS (no test case provided), but apparently it is very easy to reproduce simply by measuring networking performance.
[Fix]
AWS worked internally and found that the regression has been introduced by:
a337531b942b ("tcp: up initial rmem to 128KB and SYN rwin to around 64KB")
To solve the problem we need to apply the following upstream commit that explicitly fixes the problem introduced by the commit above:
33ae7b5bb841 ("tcp: select sane initial rcvq_space.space for big MSS")
[Regression potential]
Upstream fix that is only affecting the initial TCP buffer space and allows the TCP window size to be dynamically increased, basically restoring the previous (correct) behavior, so regression potential is minimal.
CVE References
| Changed in linux-aws (Ubuntu Bionic): | |
| importance: | Undecided → High |
| Changed in linux-aws (Ubuntu Focal): | |
| importance: | Undecided → High |
| Changed in linux-aws (Ubuntu Groovy): | |
| importance: | Undecided → High |
| Changed in linux-aws (Ubuntu Bionic): | |
| status: | New → Fix Committed |
| Changed in linux-aws (Ubuntu Focal): | |
| status: | New → Fix Committed |
| Changed in linux-aws (Ubuntu Groovy): | |
| status: | New → Fix Committed |
| Launchpad Janitor (janitor) wrote | #1 |
| Changed in linux-aws (Ubuntu Bionic): | |
| status: | Fix Committed → Fix Released |
| Launchpad Janitor (janitor) wrote | #2 |
| Changed in linux-aws (Ubuntu Focal): | |
| status: | Fix Committed → Fix Released |
| Changed in linux-aws (Ubuntu Groovy): | |
| status: | Fix Committed → Fix Released |
This bug was fixed in the package linux-aws - 4.15.0-1093.99
---------------
linux-aws (4.15.0-1093.99) bionic; urgency=medium
* bionic/linux-aws: 4.15.0-1093.99 -proposed tracker (LP: #1911275)
* aws: network performance regression due to initial TCP receive buffer size
change (LP: #1910200)
- tcp: select sane initial rcvq_space.space for big MSS
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[ Ubuntu: 4.15.0-133.137 ]
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