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Date: Sun, 22 Apr 2001 11:59:11 -0300 (BRST)
From: Rik van Riel <riel@conectiva.com.br>
To: Francis Litterio <franl@world.std.com>
Cc: linux-kernel@vger.kernel.org, kernelnewbies@nl.linux.org
Subject: Re: Does the scheduler run every time jiffies is incremented?
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[please remove linux-kernel from the CC and move it to the
 more appropriate kernelnewbies list]

On 22 Apr 2001, Francis Litterio wrote:

> 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
--
Virtual memory is like a game you can't win;
However, without VM there's truly nothing to lose...

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