On Mon, Oct 25, 2010 at 03:16:02AM -0400, Jean Delvare wrote: > Hi Arun, > > On Sun, 24 Oct 2010 21:40:38 -0400, Arun Raghavan wrote: > > Thanks again for the prompt response. One more question regarding > > coretemp: any idea how I can probe the sensor in my own source code? > > I'm hoping to be able to probe a few times a second, while the > > lm-sensors usage guide says max. probing frequency should be at most > > 0.3-0.5 Hz. > > Out of curiosity, which "usage guide" are you referring to? > > > I'm trying to measure thermal response and hence > > transients. Temperature rises rather too rapidly for this once every > > 2-3 seconds restriction; there's no intermediate reading between idle > > temperature (~28C) and loaded (~55C). Even when I overclock to > > deliberately induce more dissipation, I don't get an intermediate > > reading between the same base temperature and 70C! > > There's no reason why overclocking would help. Overclocking will > generate more heat, but the time it takes to generate it won't change. > > > Please let me know if the 2-3s resolution is a limitation of the > > sensors API or the kernel module itself. Any tips on how I might be > > able to measure with greater frequency (apart from hooking up an > > external probe and thermometer)? > > There's no limitation at the sensors API level. Each kernel driver has > its own cache lifetime depending on various things, including the > number of registers to read, how fast or slow register access is, and > the driver design. > > In the case of the coretemp driver, the 1 second lifetime is pretty > arbitrary, as there are only a few registers to read (one per core) and > register access is very fast (CPU MSRs). Fenghua, Guenter, do you think > it would make sense to shorten the cache lifetime to 0.5 or even 0.25 > second? > Might be even less - eg 100ms or even 50ms - if the temperature can rise significantly in a very short period of time, as suggested above. Plus of course if the sensor updates its readings that fast. Guenter _______________________________________________ lm-sensors mailing list lm-sensors@xxxxxxxxxxxxxx http://lists.lm-sensors.org/mailman/listinfo/lm-sensors
