We experience massive problems, when putting am335x based devices into
high broadcast load environment (customer reports). To reproduce the
issue we've written following Python script
#!/usr/bin/python
# Send UDP broadcast packets
myport = 50000
import sys, time
from socket import *
if len(sys.argv) == 2:
myport = int(sys.argv[1])
s = socket(AF_INET, SOCK_DGRAM)
s.bind(('192.168.254.36', 0))
s.setsockopt(SOL_SOCKET, SO_BROADCAST, 1)
while 1:
#data = repr(time.time()) + '\n'
data = "a"
s.sendto(data, ('<broadcast>', myport))
time.sleep(0.0001)
Just running this script on a host machine and invoking "top" on the
am335x machine results in sirq showing about 90% for 600MHz CPU and
3.18.x kernel. Below example of idle "top" output for the reference:
Mem: 13432K used, 217844K free, 64K shrd, 652K buff, 4956K cached
CPU: 0% usr 0% sys 0% nic 99% idle 0% io 0% irq 0% sirq
Then I tried 4.2.0-rc4 and sirq was about 80%, then I applied both
drivers: net: cpsw: remove disable_irq/enable_irq as irq can be
masked from cpsw itself
drivers: net: cpsw: add separate napi for tx packet handling for
performance improvment
and sirq lowered to about 50%, but I have also tried evil vendor tree
3.2.0+ and sirq was about 2%. Am I missing some kernel option/setting?
Any idea, how one can make am335x with a recent kernel to keep sirq as
low as possible, when no service listens to these broadcasts?
All am335x kernels used dual_emac mode.
I have similar situation with am3517. Kernel 2.6.37 (latest official
TI kernel) shows sirq 24% and upstream 4.1.2 about 90%.
Thanks.
Regards,
Yegor
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