Public bug reported:
Utilizing kvms with ubuntu we face this inconsistent issue where an
instance only uses a single rx queue (4 vCPUs):
ethtool -S ens7 | egrep 'rx-.\.|rx_discards: '
rx_discards: 0
rx-0.packets: 2653705823
rx-0.bytes: 561319217396
rx-1.packets: 0
rx-1.bytes: 0
rx-2.packets: 0
rx-2.bytes: 0
rx-3.packets: 0
rx-3.bytes: 0
building another identical instances however sometimes works on all 4 (4
vCPUs):
ethtool -S ens6 | egrep 'rx-.\.|rx_discards: '
rx_discards: 0
rx-0.packets: 234661700
rx-0.bytes: 49678565503
rx-1.packets: 231886603
rx-1.bytes: 49022714157
rx-2.packets: 232424910
rx-2.bytes: 49313057910
rx-3.packets: 235776722
rx-3.bytes: 49863841179
Applying the following workaround to the non-working instance:
ethtool -L ens7 combined 2
ethtool -L ens7 combined 4
makes all RSS queues work properly (4). This looks like a race condition
during boot or a kernel bug.
The kernel used during the tests is:
5.4.0-81-generic #91-Ubuntu SMP Thu Jul 15 19:09:17 UTC 2021 x86_64 x86_64
x86_64 GNU/Linux
** Affects: linux (Ubuntu)
Importance: Undecided
Status: Incomplete
** Tags: focal
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https://bugs.launchpad.net/bugs/1940928
Title:
Inconsistent behavior in NIC RSS queue loading
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