From: Nathan Sullivan <nathan.sullivan@ni.com>
To: linux-rt-users@vger.kernel.org
Subject: softirq behavior during a UDP flood
Date: Fri, 1 May 2015 10:04:12 -0500 [thread overview]
Message-ID: <20150501150412.GA15483@nathan3500-linux-VM> (raw)
Hello all,
We are running 3.14.37-rt on a Xilinx Zynq based board, and have noticed some
unfortunate behavior with NAPI polling during heavy incoming traffic. Since,
as I understand it, softirqs are scheduled on the thread that caused them in
rt, the netowrk RX softirq simply runs over and over on one CPU of the system.
The network device never re-enables interupts, basically NAPI polling runs
forever and weight/budget are irrelevant with preempt-rt on.
Since we set IRQ affinity to CPU 0 for everything, this leads to the system
live-locking and becoming unusable. With full RT preemption off, things are
fine. In addition, 3.2 kernels with RT are fine as well under heavy net load.
Is this behavior due to a design tradeoff, or is it a bug?
next reply other threads:[~2015-05-01 15:04 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-01 15:04 Nathan Sullivan [this message]
2015-05-14 19:32 ` softirq behavior during a UDP flood Sebastian Andrzej Siewior
2015-05-19 7:55 ` Thomas Gleixner
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