Pid_t OSSim::contextSwitch(CPU_t cpu, Pid_t nPid)
{
// This is the process we displaced to run the target process
Pid_t oldPid=-1;
ProcessId *newProc = ProcessId::getProcessId(nPid);
I(newProc);
GProcessor *newCore=cpus.getProcessor(cpu);
I(newCore);
// Get the cpu where the target process is already running
CPU_t runCpu=(newProc->getState()==RunningState)?newProc->getCPU():-1;
// If already running on the target processor, do nothing
if(runCpu==cpu)
return -1;
// If target core has no available flows, make one
if(!newCore->availableFlows()) {
oldPid=newCore->findVictimPid();
ProcessId *oldProc=ProcessId::getProcessId(oldPid);
cpus.switchOut(cpu, oldProc);
}
// Is the target process already running on another cpu?
if(runCpu!=-1) {
// Get another process to run on original cpu
ProcessId *repProc=ProcessId::queueGet(runCpu);
// Get the target process out of old core
cpus.switchOut(runCpu, newProc);
// Get the replacement process (if any) into the old core
if(repProc)
cpus.switchIn(runCpu,repProc);
// Get the target process in the target cpu
cpus.switchIn(cpu, newProc);
} else {
// If new process not ready, make it ready
if(newProc->getState()!=ReadyState) {
// Make it prefer the target cpu
newProc->setCPU(cpu);
// Make it ready
newProc->setState(InvalidState);
cpus.makeRunnable(newProc);
// The target cpu is prefered by the target process, and
// the target cpu has available flows. Thus, the target
// process should be now running on the target cpu
I(newProc->getCPU()==cpu);
I(newProc->getState()==RunningState);
} else {
// The new process is already ready, just switch it in
cpus.switchIn(cpu,newProc);
}
}
return oldPid;
}
