- alter scheduling priority of processes
Manual Reference Pages - SCHED (8)
sched,resched,getsched - change a process scheduler/priority
sched [-h] [-v] -r|-o|-f priority program [args, ..]
resched [-h] [-v] -r|-o|-f pid [priority]
getsched [-h] pid [pid, ...]
schedutils are some utilities used to manipulate the scheduling and priority of processes on *nix systems. This
is realized with the functions found in sched.h, see the manpage for sched_setscheduler(2) for more info about
whats going on.
sched runs a new program under the specified scheduler and priority, resched is used to change the scheduler and/or
priority of already running processes identified with their pid.
getsched is a little utility that prints the scheduler and priority of running processes identified with their pid, it
does not alter anything. Usually only the superuser(root) are allowed to change scheduling parameters.
be verbose, prints out the scheduler/priority before and after its changed.
Round Robin scheduler
Other scheduler, this is the default scheduler that normal processes start under.
The scheduler is the part of the kernel that decides which process that will get the CPU next. Posix defines
three diffrent policies that can be used to decide this.
See sched_setscheduler for an in-depth explanation for the platform you use.
Other the default timesharing scheduler used by normal processes. The Other scheduler uses the lowest
priority 0 , and it cannot be set higher.
FIFO First In First Out must have a priority in the range 1-99 and uses a simple fifo queue to hold the processes
A process that is executed will continue to execute until its either preempted by a process with higher
priority, gives up the CPU (e.g. by calling sched_yield) or performs a call that blocks. Then then next
process in the queue can run.
Round Robin must have a priority in the range 1-99 and are very similar to FIFO, except it uses timesharing
between the processes in the queue, a running process will therefore give up the CPU to another process
with the same priority when it has used its time quantum.
When a process is run under another scheduler than the default (Other) it can never be preempted by a process
with a lower priority. So, if a process run under another scheduler uses the CPU heavily, or worse have e.g. a
bug that causes it to go in an infinite loop, no other process might ever run and the machine might look
completely locked, unless there is an open shell running somewhere with a even higher priority, one can
execute commands and possibly kill the process.
None known, report any you find to http://sourceforge.net/tracker/?atid=399898&group_id=30636&func=browse
Nils O. Sel�sdal <NOS@Utel.no>
| ||SCHEDUTILS (8) ||July 30, 2001 |
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