Just flashed a build off `master` and am seeing "new" error messages
starting after the network has started, a couple times,
then every 20 seconds, seemingly like clockwork.
root@test:/# dmesg | fgrep NOHZ
[ 36.955401] NOHZ: local_softirq_pending 08
[ 57.439420] NOHZ: local_softirq_pending 08
[ 98.397107] NOHZ: local_softirq_pending 08
[ 118.881226] NOHZ: local_softirq_pending 08
[ 139.356879] NOHZ: local_softirq_pending 08
[ 159.840218] NOHZ: local_softirq_pending 08
[ 180.315962] NOHZ: local_softirq_pending 08
[ 200.799979] NOHZ: local_softirq_pending 08
[ 221.275747] NOHZ: local_softirq_pending 08
[ 241.756644] NOHZ: local_softirq_pending 08
Still looking into it, but curious if anyone else is seeing this.
Linux 4.19.53
commit 629e6538a1 (openwrt/master, openwrt/HEAD, master)
Author: Christian Lamparter <redacted>
Date: Sat Jun 22 12:23:10 2019 +0200
Similar behavior on the alternate firmware on the device
commit eaad2211db
Author: Jo-Philipp Wich <redacted>
Date: Fri Jun 21 17:41:28 2019 +0200
root@test:/# dmesg | fgrep NOHZ
[ 56.800024] NOHZ: local_softirq_pending 08
[ 77.281594] NOHZ: local_softirq_pending 08
[ 97.763395] NOHZ: local_softirq_pending 08
[ 138.718065] NOHZ: local_softirq_pending 08
[ 138.720722] NOHZ: local_softirq_pending 08
[ 159.197431] NOHZ: local_softirq_pending 08
[ 200.157115] NOHZ: local_softirq_pending 08
[ 220.636004] NOHZ: local_softirq_pending 08
[ 241.116778] NOHZ: local_softirq_pending 08
[ 241.119413] NOHZ: local_softirq_pending 08
Some mention of `NOHZ: local_softirq_pending 08` back in 2012
https://groups.google.com/forum/#!topic/linux.kernel/YeH1CTNT9vU
Other mention at
https://askubuntu.com/questions/878030/occasional-dmesg-log-nohz-local-softirq-pending-08
Add nohz=off to the kernel parameters during boot to disable it.
This option causes RCU to attempt to accelerate grace periods
in order to allow CPUs to enter dynticks-idle state more quickly.
On the other hand, this option increases the overhead
of the dynticks-idle checking, particularly on systems
with large numbers of CPUs.
I'm not sure I'd consider an IPQ4019 to have "large numbers of CPUs"
but I figured I'd lay out what I have found so far.
Jeff
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