Re: BBR and TCP internal pacing causing interrupt storm with pfifo_fast

On 09. 10. 2018 19:26, Eric Dumazet wrote:

On Tue, Oct 9, 2018 at 10:22 AM Gasper Zejn [off-list ref] wrote:

quoted

On 09. 10. 2018 19:00, Eric Dumazet wrote:

quoted

On 10/09/2018 09:38 AM, Gasper Zejn wrote:

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Hello,

I am seeing interrupt storms of over 100k-900k local timer interrupts
when changing between network devices or networks with open TCP
connections when not using sch_fq (I was using pfifo_fast). Using sch_fq
makes the bug with interrupt storm go away.

That is for what kind of traffic ?

If your TCP flows send 100k-3M packets per second, then yes, the pacing timers
could be setup in the 100k-900k range.

Traffic is nowhere in that range, think of having a few browser tabs of
javascript rich
web pages open, mostly idle, for example slack, gmail or tweetdeck. No
significant
packet rate is needed, just open connections.

No idea of what is going on really. A repro would be nice.

I've tried to isolate the issue as best I could. There seems to be an
issue if the TCP socket has keepalive set and send queue is not empty
and the route goes away.

https://github.com/zejn/bbr_pfifo_interrupts_issue

Hope this helps,
Gasper