linux-kernel - Re: acpi_idle: Very idle Core i7 machine never enters C3

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Date:	Tue, 26 Jan 2010 08:59:51 -0600
From:	jeff@...rrett.org (Jeff Garrett)
To:	peng huang <huangpeng.linux@...il.com>
Cc:	linux-kernel@...r.kernel.org, Len Brown <lenb@...nel.org>,
	linux-acpi@...r.kernel.org
Subject: Re: acpi_idle: Very idle Core i7 machine never enters C3

On Tue, Jan 26, 2010 at 09:41:00PM +0900, peng huang wrote:
> Hi,
> can you show me the file /proc/acpi/processor/CPU*/power.
> and are you sure your cpu usage is 0 or nearly zero.

Yea, I'm pretty sure my cpu usage is nearly zero.  powertop shows fewer
than 20 wakeups per second, shows 99% C2 residency, top shows 100% idle,
perf top shows acpi_idle_enter_simple as the most common function
(~50%).  Very little is running on the box, and I've compiled out the
heavier parts of the kernel (such as USB)...

(It still has ordinary userspace running, e.g. udev & hal, and still has
sshd and network traffic, as examples.)

This is all consistent with a very idle machine, I think.

> this is the info of my laptop(using core 2 processors):
> powertop's output:
> Cn                Avg residency       P-states (frequencies)
> C0 (cpu running)        (10.6%)         2.00 Ghz     1.9%
> C0                0.0ms ( 0.0%)         1.67 Ghz     0.1%
> C1 mwait          0.0ms ( 0.0%)         1333 Mhz     0.0%
> C2 mwait          0.0ms ( 0.0%)         1000 Mhz    98.0%
> C3 mwait          1.1ms (89.4%)

Yea, my laptop also (also core 2) has 700-1000 wakeups/sec and spends
greater than 80% of its time in C3...  That's partly why I'm curious
about what my core i7 desktop is doing.

> and power things:
> huang@...ng-laptop:~$ cat /proc/acpi/processor/CPU0/power 
> active state:            C0
> max_cstate:              C8
> maximum allowed latency: 2000000000 usec
> states:
>     C1:                  type[C1] promotion[--] demotion[--]
> latency[001] usage[00002364] duration[00000000000000000000]
>     C2:                  type[C2] promotion[--] demotion[--]
> latency[001] usage[00070662] duration[00000000000006013816]
>     C3:                  type[C3] promotion[--] demotion[--]
> latency[017] usage[04774185] duration[00000000010838418152]
> 
> you can see C3 with powertop,so i think your BIOS has enabled Deep 
> C-state.

Here's my power files...

/proc/acpi/processor/CPU0/power:
active state:            C0
max_cstate:              C8
maximum allowed latency: 2000000000 usec
states:
    C1:                  type[C1] promotion[--] demotion[--] latency[001] usage[00001470] duration[00000000000000000000]
    C2:                  type[C2] promotion[--] demotion[--] latency[017] usage[00234416] duration[00000000017165798539]
    C3:                  type[C3] promotion[--] demotion[--] latency[017] usage[00000000] duration[00000000000000000000]
/proc/acpi/processor/CPU1/power:
active state:            C0
max_cstate:              C8
maximum allowed latency: 2000000000 usec
states:
    C1:                  type[C1] promotion[--] demotion[--] latency[001] usage[00000481] duration[00000000000000000000]
    C2:                  type[C2] promotion[--] demotion[--] latency[017] usage[00090169] duration[00000000017188463157]
    C3:                  type[C3] promotion[--] demotion[--] latency[017] usage[00000000] duration[00000000000000000000]
/proc/acpi/processor/CPU2/power:
active state:            C0
max_cstate:              C8
maximum allowed latency: 2000000000 usec
states:
    C1:                  type[C1] promotion[--] demotion[--] latency[001] usage[00000418] duration[00000000000000000000]
    C2:                  type[C2] promotion[--] demotion[--] latency[017] usage[00068874] duration[00000000017193805291]
    C3:                  type[C3] promotion[--] demotion[--] latency[017] usage[00000000] duration[00000000000000000000]
/proc/acpi/processor/CPU3/power:
active state:            C0
max_cstate:              C8
maximum allowed latency: 2000000000 usec
states:
    C1:                  type[C1] promotion[--] demotion[--] latency[001] usage[00001356] duration[00000000000000000000]
    C2:                  type[C2] promotion[--] demotion[--] latency[017] usage[00362752] duration[00000000017156707397]
    C3:                  type[C3] promotion[--] demotion[--] latency[017] usage[00000000] duration[00000000000000000000]

> 
> -huang
> 
> 2010-01-26 (火) の 02:47 -0600 に Jeff Garrett さんは書きました:
> > Hi,
> > 
> > I was trying to chase down a theory that my desktop machine (a core i7)
> > is running warm (the fan sounds like it's at full speed all the time,
> > and I think it's not always acted this way -- hence the theory).
> > 
> > powertop is never showing it spending any time in C3...
> > 
> > I compiled a kernel without USB/sound/radeon, and ran without X.  I was
> > able to get the wakeups/sec down below 20, but no time is spent in C3.
> > 
> > sysfs looks to agree with powertop here (time = 0 on C3):
> > /sys/devices/system/cpu/cpu0/cpuidle/state0/desc: CPUIDLE CORE POLL IDLE
> > /sys/devices/system/cpu/cpu0/cpuidle/state0/latency: 0
> > /sys/devices/system/cpu/cpu0/cpuidle/state0/name: C0
> > /sys/devices/system/cpu/cpu0/cpuidle/state0/power: 4294967295
> > /sys/devices/system/cpu/cpu0/cpuidle/state0/time: 457
> > /sys/devices/system/cpu/cpu0/cpuidle/state0/usage: 59
> > /sys/devices/system/cpu/cpu0/cpuidle/state1/desc: ACPI FFH INTEL MWAIT 0x0
> > /sys/devices/system/cpu/cpu0/cpuidle/state1/latency: 1
> > /sys/devices/system/cpu/cpu0/cpuidle/state1/name: C1
> > /sys/devices/system/cpu/cpu0/cpuidle/state1/power: 1000
> > /sys/devices/system/cpu/cpu0/cpuidle/state1/time: 308177
> > /sys/devices/system/cpu/cpu0/cpuidle/state1/usage: 3975
> > /sys/devices/system/cpu/cpu0/cpuidle/state2/desc: ACPI FFH INTEL MWAIT 0x10
> > /sys/devices/system/cpu/cpu0/cpuidle/state2/latency: 17
> > /sys/devices/system/cpu/cpu0/cpuidle/state2/name: C2
> > /sys/devices/system/cpu/cpu0/cpuidle/state2/power: 500
> > /sys/devices/system/cpu/cpu0/cpuidle/state2/time: 873440787
> > /sys/devices/system/cpu/cpu0/cpuidle/state2/usage: 239038
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/desc: ACPI FFH INTEL MWAIT 0x20
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/latency: 17
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/name: C3
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/power: 350
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/time: 0
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/usage: 0
> > 
> > This may be a complete red herring, but I added some printk logic to
> > acpi_idle_bm_check(), and it is getting called often, but bm_status is
> > always 1.  [I infer from this that the idle logic is trying to go into
> > C3, but this check is stopping it...  Unless I misread something.]
> > 
> > Is this expected behavior or is this a legitimate problem?
> > 
> > How might I investigate this further?
> > 
> > Attaching dmesg, /proc/cpuinfo, powertop -d output.
> > 
> > Thanks,
> > Jeff Garrett
> 
> 
> -- 
> peng huang <huangpeng.linux@...il.com>
> 
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