Hi Kapil,
On Fri, 19 Jul 2013 11:28:28 -0400, Kapil Dev wrote:
> I have a couple of queries about lm-sensors package.
>
> 1) The FAQ section in chapter-1 says that the drivers update their values every 1 sec. I am aware of the fact that reading the sensors more frequently will affect the performance as it is intrusive to CPU to read an MSR, but I need to read the core-temperature values at faster rate for a project. Would you tell me what changes I should make to read the sensors faster? In particular, I want to read the core temperature (I believe it is done in coretemp.c through IA32_THERMAL_STATUS MSR register). coretemp.c seems to have "jiffy" as time stamp, if I change it in the coretemp.c, will it work? Or, is there any other file that needs to be changed during kernel-compilation?
Just change this condition in show_temp():
/* Check whether the time interval has elapsed */
if (!tdata->valid || time_after(jiffies, tdata->last_updated + HZ)) {
to just:
/* Always update */
if (1) {
This will let you read the value as frequently as you want. Or if you
want to keep a safety guard, you can simply change HZ to HZ/10 (read
every 0.1 s max) or HZ/100 (read every 0.01 s max.)
> 2) Does the lm-sensor package use the correct value of Tjmax (the temp value at which PROCHOT signal goes high) automatically based on the processor brand and type? I noticed that the Tjmax =100C is used in core temp.c, but the 22nm intel processor that I am working on has Tjmax of 105C. Do I need to change it myself?
We have a complex heuristic to figure out the right TjMax value, but
Intel made it such a mess that it is very difficult. So it really is
best effort. If the driver has TjMax wrong for your CPU, please let us
know what kernel version you are running, what CPU model you have is
and where you found the correct TjMax value.
Then you can either try to fix it in the driver itself, or adjust it
from userspace by adding this to /etc/sensors.d/coretemp.conf:
chip "coretemp-*"
compute temp1 @+5, @-5
compute temp2 @+5, @-5
compute temp3 @+5, @-5
compute temp4 @+5, @-5
compute temp5 @+5, @-5
(Adjust for your own case...)
Hope that helps,
--
Jean Delvare
http://khali.linux-fr.org/wishlist.html
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