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.
However sometimes the computer takes a very long time (20 seconds to -- I think -- 15 minutes or more) to react to a change in the load. I have run commands like "stress --cpu 1" or "stress --cpu 8" and watched i7z. When the governor is powersave it may stay at 800MHz and when the governor is performance it may stay between 1000MHz to 1400MHz. If I leave the stress running long enough it seems like eventually the frequency will go up to the expected values. Once the CPU frequency goes up I can keep it up by leaving the stress running and my applications are responsive. If I kill the stress process, the system may or may not respond quickly to changes in load.
There is some googleable discussion about the BIOS limiting the frequency for Thinkpads. However, the value in
/sys/module/processor/parameters/ignore_ppc
does not seem to matter though and the file
/sys/devices/system/cpu/cpu0/cpufreq/bios_limit
is never present. Also the system will respond when I change the
governor from performance to powersave and back which does not seem
consistent with a limit provided by the BIOS.
Does anyone know what could be wrong or how I can debug this? -Timothy
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