Messages in this thread | | | Date | Thu, 4 Apr 2013 18:10:14 +0000 | From | Christoph Lameter <> | Subject | Re: [RFC GIT PULL] nohz: Kconfig layout improvements |
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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?)
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