Re: sched /HT processor

[Steven Rostedt <rostedt@goodmis.org>]

On Mon, 2005-04-04 at 04:22 +0530, Arun Srinivas wrote:
> Thanks. yes, a reschedule may not take place after a ms, if the currently 
> running task cannot be preempted by another task.
> 
> (1) But, can a reschedule happen within a millisec (or once a process is 
> scheduled can schedule() be called before the next millisec.) ?
> 

Yes.  For example: a high priority task may be waiting for some IO to
come in. Right after the normal timer interrupt scheduled another task,
the IO may come in and wake the high priority process up. This process
will preempt the other task right away. (ie. less than 1 ms).

> 2) Also in case argument (1) is not true, and I want rescheduling to be done 
> (i.e., schedule() called) in less than 1 ms , can I directly change the HZ 
> value in <asm-i386/param.h> and recompile my kernel so that my timer 
> interrupt will occur frequently?
> 

Well, 1) is true, but you can also increase HZ over 1000 if you like,
but that will usually cause more overhead, since, although a schedule
may not take place every HZ, a timer interrupt will.

-- Steve