Michael Matz
On Wed, 1 Aug 2007, Andreas Jaeger wrote:
Cn Avg residency (3s) P-states (frequencies) C0 (cpu running) ( 2.0%) C1 0.0ms ( 0.0%) 1400 Mhz 33.0% C2 7.4ms (48.8%) 1300 Mhz 0.0% C3 7.6ms (30.3%) 1200 Mhz 0.0% C4 4.7ms (18.9%) 600 Mhz 67.0% Wakeups-from-idle per second : 145.7 Power usage (ACPI estimate): 12.1W (0.9 hours)
vs.
Cn Avg residency (10s) P-states (frequencies) C0 (cpu running) ( 5.4%) C1 0.0ms ( 0.0%) 1400 Mhz 0.0% C2 2.9ms (42.0%) 1300 Mhz 0.0% C3 3.3ms (14.2%) 1200 Mhz 0.0% C4 3.2ms (38.5%) 600 Mhz 100.0% Wakeups-from-idle per second : 307.5 Power usage (ACPI estimate): 10.5W (1.0 hours) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
So, for me the nohz kernel uses more power. This seems to be a result From running on an idle system with 33% on high power.
How often does the ondemand governor sample for busyness? % cat /sys/devices/system/cpu/cpu*/cpufreq/ondemand/sampling_rate
/sys/devices/system/cpu/cpu0/cpufreq/ondemand/sampling_rate 500000 /sys/devices/system/cpu/cpu0/cpufreq/ondemand/sampling_rate_min 250000 cat /sys/devices/system/cpu/cpu0/cpufreq/ondemand/sampling_rate_max 250000000
(and compare with sampling_rate_max, try playing with echoing different values int sampling_rate). But it's strange nevertheless, as you have less wakeups with nohz, as expected. Are you sure that the system at the time you measured with nohz really was as idle as with nohz=off? No ugly indexer running?
(FWIW: my power consumption goes down with nohz)
Yes, it was idle, Andreas -- Andreas Jaeger, Director Platform/openSUSE, aj@suse.de SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG Nürnberg) Maxfeldstr. 5, 90409 Nürnberg, Germany GPG fingerprint = 93A3 365E CE47 B889 DF7F FED1 389A 563C C272 A126