It the first time I write in this forum, but I read the messages very often.
I have read the books "Understanding The Linux Kernel 2nd Edition". Wonderful book.
I cannot understand a simple thing about the scheduler of kernel 2.4.x.
I know that the timer interrupt stops the CPU every 10ms (0.010) and executes the following operation:
current->counter--;
to decrement the counter of the current process.
I don't understand one point. I will try to describe my problem with a simple example.
Suppose we have 2 processes, A and B.
At the time 0 the process A starts, it uses the CPU until the instant of time 0.009 (9ms).
At this instant of time the process A tries to read a key from the keyboard, but there are not key in the keyboard buffer,so the process A is stopped waiting for the pression of a key.
So the scheduler at the instand 9ms begin to run the process B. After few time (1ms) happens a timer interrupt, and the processB->counter is decremented.
BUT THIS IS NOT FAIR ! The CPU has been used from the process A, but the counter of the process B has been decremented !
This is the point I cannot understand.
Thanks in advance.
Paolo Minazzi
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