Re: ixgbe: ksoftirqd consumes 100% CPU w/ ~50 TCP conns

Hello Everyone-

So we tracked it down to IOMMU causing CPU affinity getting broken[1].
Can we provide any further details or is this a known issue?

Thank You,

Brandon

[1] https://github.com/coreos/bugs/issues/1275#issuecomment-219866601

On Tue, May 17, 2016 at 12:44 PM, Brandon Philips [off-list ref] wrote:

Hello ixgbe team-

With Linux v4.6 and the ixgbe driver (details below) a user is reporting
ksoftirqd consuming 100% of the CPU on all cores after a moderate  ~20-50
number of TCP connections. They are unable to reproduce this issue with
Cisco hardware.

With Kernel v3.19 they cannot reproduce[1] the issue. Disabling IOMMU
(intel_iommu=off) does "fix" the issue[2].

Thank You,

Brandon

[1] https://github.com/coreos/bugs/issues/1275#issuecomment-219157803
[2] https://github.com/coreos/bugs/issues/1275#issuecomment-219819986

Intel Corporation 82599ES 10-Gigabit SFI/SFP+ Network Connection (rev 01)
ethtool -i eno1
driver: ixgbe
version: 4.0.1-k
firmware-version: 0x800004e0
bus-info: 0000:06:00.0
supports-statistics: yes
supports-test: yes
supports-eeprom-access: yes
supports-register-dump: yes
supports-priv-flags: no

CPU
Intel(R) Xeon(R) CPU E5-2690 v3 @ 2.60GHz