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

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Date:	Tue, 24 May 2016 09:40:14 -0700
From:	Brandon Philips <brandon@...p.co>
To:	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	John Fastabend <john.fastabend@...il.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	Mark Rustad <mark.d.rustad@...el.com>
Cc:	netdev@...r.kernel.org, Matthew Garrett <mjg59@...f.ucam.org>
Subject: 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 <brandon@...p.co> 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