Messages in this thread | | | From | "Arun Srinivas" <> | Subject | scheduler/SCHED_FIFO behaviour | Date | Tue, 05 Apr 2005 04:36:42 +0530 |
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I am scheduling 2 SCHED_FIFO processes and set them affinity( process A runs on processor 1 and process B runs on processor 2), on a HT processor.(I did this cause I wanted to run them together).Now, in schedule() I measure the timedifference between when they are scheduled. I found that when I introduce these 2 processes as SCHED_FIFO they are
1)scheduled only once and run till completion ( they running time is around 2 mins.) 2)entire system appears frozen....no mouse/key presses detected until the processes exit.
From what I observed does it mean that even the OS / interrupt handler does not occur during the entire period of time these real time processes run?? (as I said the processes run in minutes). How can I verify that?
Thanks Arun
>From: Steven Rostedt <rostedt@goodmis.org> >To: Arun Srinivas <getarunsri@hotmail.com> >CC: juhl-lkml@dif.dk, LKML <linux-kernel@vger.kernel.org> >Subject: Re: sched /HT processor >Date: Sun, 03 Apr 2005 19:08:06 -0400 > >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 > >
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