Re: [RFC GIT PULL] nohz: Kconfig layout improvements

[Christoph Lameter]

It seems that nohz still has no effect.

3.9-rc5 + patches. Affinity of init set to 0,1 so no
tasks are running on 9. The "latencytest" used here is part of my
lldiag-0.15 toolkit.

First test without any special kernel parameters. nohz off right?

$ nice -5 taskset -c 9 latencytest

CPUs: Freq=2.90Ghz Processors=32 Cores=8 cacheline_size=64 Intel(R)
Xeon(R) CPU E5-2690 0 @ 2.90GHz
16775106 samples below 1000 nsec
13 involuntary context switches
1019 (0.00607411%) variances in 10.00 seconds: minimum 1.07us maximum 12.32us average 3.30us stddev 0.63us

HZ=100 so the 1019 variances are likely timer interrupts.




After nohz setup

/proc/cmdline:

BOOT_IMAGE=/vmlinuz-3.9.0-rc5+ root=/dev/mapper/vg01-root ro console=tty0 console=ttyS0,115200 idle=mwait rcu_nocb_poll rcu_nocbs=2-31 nohz_extended=2-31

$ nice -5 taskset -c 9 latencytest
CPUs: Freq=2.90Ghz Processors=32 Cores=8 cacheline_size=64 Intel(R)
Xeon(R) CPU E5-2690 0 @ 2.90GHz
16779362 samples below 1000 nsec
13 involuntary context switches
1037 (0.00617983%) variances in 10.00 seconds: minimum 1.00us maximum 10.61us average 3.30us stddev 0.98us



If I move the RCU threads off the cpu then I get a slightly better result:

$ nice -5 taskset -c 9 latencytest
CPUs: Freq=2.90Ghz Processors=32 Cores=8 cacheline_size=64 Intel(R)
Xeon(R) CPU E5-2690 0 @ 2.90GHz
16796039 samples below 1000 nsec
12 involuntary context switches
1020 (0.00607249%) variances in 10.00 seconds: minimum 1.00us maximum 11.58us average 2.77us stddev 0.55us



Why is the tick not stopping? How do I diagnose this? (I can start
patching the kernel again like last time but isnt there a better way?)


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/