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Bug 2128448 - [Azure][RHEL-9] UDP data loss is big at packets larger than MTU even without vRSS hashing
Summary: [Azure][RHEL-9] UDP data loss is big at packets larger than MTU even without ...
Keywords:
Status: CLOSED MIGRATED
Alias: None
Product: Red Hat Enterprise Linux 9
Classification: Red Hat
Component: kernel
Version: 9.1
Hardware: Unspecified
OS: Unspecified
high
medium
Target Milestone: rc
: ---
Assignee: Maxim Levitsky
QA Contact: Li Tian
URL:
Whiteboard:
Depends On: 2128446
Blocks:
TreeView+ depends on / blocked
 
Reported: 2022-09-20 14:59 UTC by Li Tian
Modified: 2023-09-22 14:26 UTC (History)
9 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of: 2128446
Environment:
Last Closed: 2023-09-22 14:26:43 UTC
Type: Bug
Target Upstream Version:
Embargoed:
pm-rhel: mirror+

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Issue Tracker   RHEL-7219 0 None Migrated None 2023-09-22 14:26:38 UTC
Red Hat Issue Tracker RHELPLAN-139244 0 None None None 2022-11-14 06:38:57 UTC

Description Li Tian 2022-09-20 14:59:54 UTC 
+++ This bug was initially created as a clone of Bug #2128446 +++

Description of problem:
UDP data loss is supposed be less then 1% in the below situation.
1. vRSS hashing excludes the port where UDP data is through.
# ethtool -n eth0 rx-flow-hash udp4
UDP over IPV4 flows use these fields for computing Hash flow key:
IP SA
IP DA
2. Packets length is larger than MTU, e.g. 8k.

Tested with 2 Standard_D15_v2 VMs using the below commands on each respectively:
# iperf3 -s 4 -p 8001
# iperf3 -u -c 10.0.0.4 -p 8001 -4 -b 0 -l 8k -P 64 -t 60 --get-server-output -i 60

And the result is:
[ ID] Interval           Transfer     Bitrate         Jitter    Lost/Total Datagrams
[  5]   0.00-60.01  sec  1.09 MBytes   152 Kbits/sec  4.741 ms  31221/31360 (1e+02%)  receiver
[  6]   0.00-60.01  sec   944 KBytes   129 Kbits/sec  3.708 ms  30642/30760 (1e+02%)  receiver
...
[SUM]   0.00-60.01  sec  55.2 MBytes  7.71 Mbits/sec  5.510 ms  1646217/1653281 (1e+02%)  receiver

Version-Release number of selected component (if applicable):
5.14.0-162.el9.x86_64

How reproducible:
100% on Azure.

Steps to Reproduce:
1. Create 2 VMs and disable vRSS hashing by - 
# ethtool -N eth0 rx-flow-hash udp4 sd
2. run iperf3 commands in description individually.

Actual results:
Data loss is greater than 1%.

Expected results:
Data loss is less than 1%.

Additional info:
1. This issue presents from 8.6 through 9.1.
2. Related BZ - https://bugzilla.redhat.com/show_bug.cgi?id=1474300 (looks like a re-occurrence).
3. Issue does not present when packets are smaller than MTU.
4. Issue presents on other VM sizes, e.g. Standard_D16s_v5.
Comment 5 Li Tian 2023-02-27 02:55:14 UTC 
Still presents on latest 9.2 (5.14.0-277.el9.x86_64):

[ ID] Interval           Transfer     Bitrate         Jitter    Lost/Total Datagrams
[  5]   0.00-60.01  sec   672 KBytes  91.7 Kbits/sec  0.327 ms  80682/80766 (1e+02%)  receiver
[  6]   0.00-60.01  sec   760 KBytes   104 Kbits/sec  0.213 ms  80686/80781 (1e+02%)  receiver
...
[SUM]   0.00-60.01  sec  44.6 MBytes  6.24 Mbits/sec  0.243 ms  5163510/5169224 (1e+02%)  receiver
Comment 11 RHEL Program Management 2023-09-22 14:24:18 UTC 
Issue migration from Bugzilla to Jira is in process at this time. This will be the last message in Jira copied from the Bugzilla bug.
Comment 12 RHEL Program Management 2023-09-22 14:26:43 UTC 
This BZ has been automatically migrated to the issues.redhat.com Red Hat Issue Tracker. All future work related to this report will be managed there.

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