debugging sluggish CPU frequency transitions

Timothy Redmond tredmond59 at
Thu Nov 13 17:30:11 UTC 2014

On 11/13/2014 02:23 AM, Roberto Ragusa wrote:
> On 11/13/2014 04:52 AM, Timothy Redmond wrote:
>> I have a Thinkpad W520 computer (4270CTO) and I am running Fedora 20 and keeping its packages up to date.  Often when I am working the cpu frequency transitions beautifully and the computer is very responsive. I have run some programs that take a long time (hours to days) and have watched the frequency go up when there is only one thread running and go down when there are several threads running. So it seems to be working very nicely.
> My W520 (on F19) does not show this problem.
> Have a look at system messages; there could be thermal related limits
> which are enforced even if the load and preferences would like to
> have a high speed.
I am actually pretty happy if this is not a common problem because it 
means I probably won't see it on my next machine.

I do get messages about thermal events but I don't think that this is 
the problem.  These messages look like this:

    Nov 13 09:12:45 Neptune mcelog[1203]: Hardware event. This is not a software error.
    Nov 13 09:12:45 Neptune mcelog[1203]: MCE 0
    Nov 13 09:12:45 Neptune mcelog[1203]: CPU 3 THERMAL EVENT TSC 8c06f1a9b8f7
    Nov 13 09:12:45 Neptune mcelog[1203]: TIME 1415898623 Thu Nov 13 09:10:23 2014
    Nov 13 09:12:45 Neptune mcelog[1203]: Processor 3 heated above trip temperature. Throttling enabled.
    Nov 13 09:12:45 Neptune mcelog[1203]: Please check your system cooling. Performance will be impacted
    Nov 13 09:12:45 Neptune mcelog[1203]: STATUS 8803000b MCGSTATUS 0
    Nov 13 09:12:45 Neptune mcelog[1203]: MCGCAP c09 APICID 3 SOCKETID 0
    Nov 13 09:12:45 Neptune mcelog[1203]: CPUID Vendor Intel Family 6 Model 42

These messages are followed by

    Nov 13 09:21:17 Neptune kernel: CPU3: Core temperature/speed normal

a few seconds later.

I don't think that this is the problem because these messages only show 
up once turbo-boost kicks in and is working properly.   In addition when 
the frequency doesn't go up to expected levels the machine -- based on 
the sensor information that I can see -- the machine is pretty cool.

Also I almost have the impression that the machine is more responsive 
when it is warm.  It is responsive now and there is a firefox program 
that has been running overnight at something like 40% (I have something 
like fifteen windows/tabs open and one of them somewhere thinks that 
there is work to do).

I didn't always get these messages - they came with some update (I was 
running ubuntu in those days).

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