How frequently is the
proc file system updated on Linux? Is it 20 milliseconds (time quantum)?
The information that you read from the proc filesystem is not stored on any media (not even in RAM), so there is nothing to update.
The purpose of the proc file system is to allow userspace programs to obtain or set kernel data using the simple and familiar file system semantics (
lseek), even though the data that is read or written doesn't reside on any media. This design decision was deemed better (e.g. human readable and easily scriptable) for getting and setting data whose format could not be specified in advance than implementing something such as ASN1 encoded OIDs, which also would have worked fine.
The data that you see when you read from the proc filesystem is generated on-the-fly when you do a read from the begining of a file. That is, doing the read causes the data to be generated by a kernel callback function that is specific to the file you are reading. Doing an
lseek to the begining of the file and reading again causes another call to the callback that generates the data again. Similarly, when you write to a writable file in the proc filesystem, a callback function is called that parses the input and sets kernel variables. The input data in it's raw form isn't stored.
The above is just a slightly more verbose way of saying what Hauke Laging states so succinctly. I suggest that you accept his answer.