Does the scheduler run every time jiffies is incremented?
I'm reading Rubini's "Linux Device Drivers" and it isn't clear to me whether the scheduler runs every time the timer interrupt increments jiffies or less frequently.
Does the scheduler run every time jiffies is incremented? --
Francis Litterio
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Quoted 5 lines · Francis Litterio
I'm reading Rubini's "Linux Device Drivers" and it isn't clear to me whether the scheduler runs every time the timer interrupt increments jiffies or less frequently.
Does the scheduler run every time jiffies is incremented?
No. Every timer interrupt a bunch of functions in kernel/timer.c is run, amongst them the following lines of code (from update_process_times):
if (--p->counter <= 0) {
p->counter = 0;
p->need_resched = 1;
}As you can see, we will only reschedule when the time slice of the currently running process is over.
regards,
Rik
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Quoted 1 line · Francis Litterio
Does the scheduler run every time jiffies is incremented?
No, it runs when something needs to be rescheduled (ie, when the current tasks need_resched element (current->need_resched) is set). This typically happens when someone wakes up, or the task reaches the end of its allotted quantum.
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