b4cf88a04f
- cotributed by Bjorn Swift - In this first phase, scheduling is moved from the kernel to the PM server. The next steps are to a) moving scheduling to its own server and b) include useful information in the "out of quantum" message, so that the scheduler can make use of this information. - The kernel process table now keeps record of who is responsible for scheduling each process (p_scheduler). When this pointer is NULL, the process will be scheduled by the kernel. If such a process runs out of quantum, the kernel will simply renew its quantum an requeue it. - When PM loads, it will take over scheduling of all running processes, except system processes, using sys_schedctl(). Essentially, this only results in taking over init. As children inherit a scheduler from their parent, user space programs forked by init will inherit PM (for now) as their scheduler. - Once a process has been assigned a scheduler, and runs out of quantum, its RTS_NO_QUANTUM flag will be set and the process dequeued. The kernel will send a message to the scheduler, on the process' behalf, informing the scheduler that it has run out of quantum. The scheduler can take what ever action it pleases, based on its policy, and then reschedule the process using the sys_schedule() system call. - Balance queues does not work as before. While the old in-kernel function used to renew the quantum of processes in the highest priority run queue, the user-space implementation only acts on processes that have been bumped down to a lower priority queue. This approach reacts slower to changes than the old one, but saves us sending a sys_schedule message for each process every time we balance the queues. Currently, when processes are moved up a priority queue, their quantum is also renewed, but this can be fiddled with. - do_nice has been removed from kernel. PM answers to get- and setpriority calls, updates it's own nice variable as well as the max_run_queue. This will be refactored once scheduling is moved to a separate server. We will probably have PM update it's local nice value and then send a message to whoever is scheduling the process. - changes to fix an issue in do_fork() where processes could run out of quantum but bypassing the code path that handles it correctly. The future plan is to remove the policy from do_fork() and implement it in userspace too.
42 lines
1.3 KiB
C
42 lines
1.3 KiB
C
#include "../system.h"
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#include <signal.h>
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#include <sys/sigcontext.h>
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#include <minix/endpoint.h>
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/*===========================================================================*
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* do_schedule *
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*===========================================================================*/
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PUBLIC int do_schedule(struct proc * caller, message * m_ptr)
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{
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struct proc *p;
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p = proc_addr(_ENDPOINT_P(m_ptr->SCHEDULING_ENDPOINT));
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/* Make sure the priority number given is within the allowed range.*/
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if (m_ptr->SCHEDULING_PRIORITY < TASK_Q ||
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m_ptr->SCHEDULING_PRIORITY > NR_SCHED_QUEUES)
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return(EINVAL);
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/* Only system processes can schedule processes */
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if (! (priv(caller)->s_flags & SYS_PROC))
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return(EPERM);
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/* Only this process' scheduler can schedule it */
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if (caller != p->p_scheduler)
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return(EPERM);
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/* In some cases, we might be rescheduling a runnable process. In such
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* a case (i.e. if we are updating the priority) we set the NO_QUANTUM
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* flag before the generic unset to dequeue/enqueue the process
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*/
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if (proc_is_runnable(p))
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RTS_SET(p, RTS_NO_QUANTUM);
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/* Clear the scheduling bit and enqueue the process */
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p->p_priority = m_ptr->SCHEDULING_PRIORITY;
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p->p_ticks_left = m_ptr->SCHEDULING_QUANTUM;
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RTS_UNSET(p, RTS_NO_QUANTUM);
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return(OK);
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}
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