I saw that /proc/cpuinfo update all the time, especially the field "cpu MHz"? I assumed that these details should be constant.
When did /proc/cpuinfo begin to update all the time, especially the field "cpu MHz"? Is it depend linux systems or versions?
Example :
[omerha@hroor tmp]$ cat /proc/cpuinfo | grep "cpu MHz" | tail -1
cpu MHz : 1406.195
[omerha@hroor tmp]$ cat /proc/cpuinfo | grep "cpu MHz" | tail -1
cpu MHz : 1675.964
It depends on the processor architecture. For x86 (32-bit a.k.a. i386 or 64-bit a.k.a x86_64 a.k.a. amd64), it was generalized in kernel 2.6.16 which came out in March 2006. The patch generalizing it had been under discussion and review for a while.
In the code (for 32-bit x86): 2.6.16 calls cpufreq_quick_get which looks up the current value for each CPU. 2.6.15 reads a global variable which is only updated on some processors and is never updated on multiprocessor machines.
There is no file to update. The CPU frequency changes when it changes.
The "file", it looks like a file but is not a file: it does not exist on disk or SSD. It has a filename, it has content (so it is a file, and so is a directory, a sym-link, a hard-disk, a serial-port, … ). In general values in /proc are generated dynamically whenever they are read.
