Re: [PATCH] ACPI, CPU_IDLE: Add more information about C-states

[Len Brown <lenb@kernel.org>]

On Thursday 14 February 2008 11:52, Pallipadi, Venkatesh wrote:
> 
> 'usage' is a counter that counts every time we get into poll_idle
> routine. I also try to keep track of time spent in poll_idle, until
> need_resched sends us out. That time is accumulated in 'time'.
> Just have those to be consistent with other state and to be sure that
> powertop kind of tools wont get confused.

yes, the consistency is good.
But my question is when and why we enter poll_idle at all.

> I agree with the 'power' number. I did not like that 4294967295 there.
> But, I had to put some number higher than other C-states, maximum
> possible seemed logical. May be I can change the sysfs interface to
> print <NULL> or something like that for power?

I dunno.  Somehow I like 0 to signify an unknown quantity
rather than a huge number.  If somebody actually looks at it
with a program,  they're going to have to special case either of them,
and 0 seems simpler.

thanks,
-Len


> >
> >I'm confused by state0 -- why are usage and time non-zero --
> >is this due to some residency there during initialization?
> >
> >I don't know if I like the looks of 2^32 - 1 as the power number...
> >
> >-Len
> >
> >[root@t61 cpuidle]# cat /proc/acpi/processor/CPU0/power
> >active state:            C0
> >max_cstate:              C8
> >bus master activity:     00000000
> >maximum allowed latency: 2000000000 usec
> >states:
> >    C1:                  type[C1] promotion[--] demotion[--] 
> >latency[001] usage[00000000] duration[00000000000000000000]
> >    C2:                  type[C2] promotion[--] demotion[--] 
> >latency[001] usage[00000161] duration[00000000000000018522]
> >    C3:                  type[C3] promotion[--] demotion[--] 
> >latency[017] usage[00088238] duration[00000000002957934702]
> >[root@t61 cpuidle]# grep . */*
> >state0/desc:CPUIDLE CORE POLL IDLE
> >state0/latency:0
> >state0/name:C0
> >state0/power:4294967295
> >state0/time:11623
> >state0/usage:6
> >state1/desc:ACPI FFH INTEL MWAIT 0x0
> >state1/latency:1
> >state1/name:C1
> >state1/power:1000
> >state1/time:0
> >state1/usage:0
> >state2/desc:ACPI FFH INTEL MWAIT 0x10
> >state2/latency:1
> >state2/name:C2
> >state2/power:500
> >state2/time:5104
> >state2/usage:163
> >state3/desc:ACPI FFH INTEL MWAIT 0x20
> >state3/latency:17
> >state3/name:C3
> >state3/power:250
> >state3/time:830738297
> >state3/usage:89280
> >
> >of course this isnt' new with this patch -- 2.6.25-rc1 looks as below:
> >
> >[root@t61 cpuidle]# cat /proc/acpi/processor/CPU0/power
> >active state:            C0
> >max_cstate:              C8
> >bus master activity:     00000000
> >maximum allowed latency: 2000000000 usec
> >states:
> >    C1:                  type[C1] promotion[--] demotion[--] 
> >latency[001] usage[00000000] duration[00000000000000000000]
> >    C2:                  type[C2] promotion[--] demotion[--] 
> >latency[001] usage[00000202] duration[00000000000000028172]
> >    C3:                  type[C3] promotion[--] demotion[--] 
> >latency[017] usage[00026011] duration[00000000000264174466]
> >[root@t61 cpuidle]# grep . */*
> >state0/latency:0
> >state0/name:C0 (poll idle)
> >state0/power:4294967295
> >state0/time:35713
> >state0/usage:6
> >state1/latency:1
> >state1/name:C1
> >state1/power:1000
> >state1/time:0
> >state1/usage:0
> >state2/latency:1
> >state2/name:C2
> >state2/power:500
> >state2/time:7771
> >state2/usage:203
> >state3/latency:17
> >state3/name:C3
> >state3/power:250
> >state3/time:74950731
> >state3/usage:26286
> >
> >and 2.6.24 showed no C0, as expected.
> >
> >[root@t61 cpuidle]# cat /proc/acpi/processor/CPU0/power
> >active state:            C0
> >max_cstate:              C8
> >bus master activity:     00000000
> >maximum allowed latency: 2000 usec
> >states:
> >    C1:                  type[C1] promotion[--] demotion[--] 
> >latency[001] usage[00000030] duration[00000000000000000000]
> >    C2:                  type[C2] promotion[--] demotion[--] 
> >latency[001] usage[00000714] duration[00000000000000531448]
> >    C3:                  type[C3] promotion[--] demotion[--] 
> >latency[017] usage[00020563] duration[00000000000168147357]
> >[root@t61 cpuidle]# grep . */*
> >state0/latency:1
> >state0/name:C1
> >state0/power:1000
> >state0/time:0
> >state0/usage:30
> >state1/latency:1
> >state1/name:C2
> >state1/power:500
> >state1/time:148317
> >state1/usage:719
> >state2/latency:17
> >state2/name:C3
> >state2/power:250
> >state2/time:48238649
> >state2/usage:21034
> >[root@t61 cpuidle]#                        
> >
>