03-06-2013
Quote:
Originally Posted by
DGPickett
In a more perfect world, the dispatcher would get the CPU to programs that do not hog it and that do i/o on an expedited basis.
I believe many schedulers do; I've always been impressed by how well UNIX in general timeshares, compared to Windows' nonstop stuttering. (Not even quad cores helps.) But it only works when they're equal priority... High priority will be favored over low priority regardless of how polite they are. That's what priority's for.
A runaway higher-priority process can lock lower-priority ones out quite harshly; users with the ability to raise their priority can badly affect other users. Starting them at maximum relative to each other prevents them from stalling each other.
Last edited by Corona688; 03-06-2013 at 05:47 PM..
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LEARN ABOUT OPENSOLARIS
nice
nice(2) System Calls nice(2)
NAME
nice - change priority of a process
SYNOPSIS
#include <unistd.h>
int nice(int incr);
DESCRIPTION
The nice() function allows a process to change its priority. The invoking process must be in a scheduling class that supports the nice().
The nice() function adds the value of incr to the nice value of the calling process. A process's nice value is a non-negative number for
which a greater positive value results in lower CPU priority.
A maximum nice value of (2 * NZERO) -1 and a minimum nice value of 0 are imposed by the system. NZERO is defined in <limits.h> with a
default value of 20. Requests for values above or below these limits result in the nice value being set to the corresponding limit. A nice
value of 40 is treated as 39.
Calling the nice() function has no effect on the priority of processes or threads with policy SCHED_FIFO or SCHED_RR.
Only a process with the {PRIV_PROC_PRIOCNTL} privilege can lower the nice value.
RETURN VALUES
Upon successful completion, nice() returns the new nice value minus NZERO. Otherwise, -1 is returned, the process's nice value is not
changed, and errno is set to indicate the error.
ERRORS
The nice() function will fail if:
EINVAL The nice() function is called by a process in a scheduling class other than time-sharing or fixed-priority.
EPERM The incr argument is negative or greater than 40 and the {PRIV_PROC_PRIOCNTL} privilege is not asserted in the effective set of
the calling process.
USAGE
The priocntl(2) function is a more general interface to scheduler functions.
Since -1 is a permissible return value in a successful situation, an application wishing to check for error situations should set errno to
0, then call nice(), and if it returns -1, check to see if errno is non-zero.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Interface Stability |Standard |
+-----------------------------+-----------------------------+
|MT-Level |Async-Signal-Safe |
+-----------------------------+-----------------------------+
SEE ALSO
nice(1), exec(2), priocntl(2), getpriority(3C), attributes(5), privileges(5), standards(5)
SunOS 5.11 1 Apr 2004 nice(2)