kern_cpureserve.cxx

C++ 编写的EROS RTOS

/*
 * Copyright (C) 1998, 1999, Jonathan S. Shapiro.
 *
 * This file is part of the EROS Operating System.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2,
 * or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/* Data structures for reserve management.  The current kernel
 * implementation uses a fixed-priority strategy for implementing
 * cpu reserves.
 */

#include <kerninc/kernel.hxx>
#include <kerninc/Thread.hxx>
#include <kerninc/CpuReserve.hxx>
#include <kerninc/Machine.hxx>
#include <kerninc/PhysMem.hxx>
#include <arch-kerninc/KernTune.hxx>
#include <eros/Reserve.h>

const int DEFAULT_SCHED_QUANTA = 10; /* in ms */

CpuReserve *CpuReserve::Current = 0;

/* Reserves associated with ordinary schedule keys -- the 'priority'
 * is actually an index into the reserve table:
 */

CpuReserve *CpuReserve::CpuReserveTable;

/* Processes that lack a schedule capability need a reserve that they
 * can be parked on so as to ensure that they are never scheduled. The
 * priority of this reserve needs to be BELOW the idle priority.
 */
CpuReserve CpuReserve::InactiveReserve(Prio::Inactive);

/* Idle thread requires it's own scheduling reserve, as the user-level
 * idle reserve is actually higher priority than this one.
 */
CpuReserve CpuReserve::KernIdleCpuReserve(Prio::KernIdle);

/* Other kernel threads require their own copy of the normal priority
 * reserve because the reserve table isn't allocated yet when we
 * allocate some of the early kernel threads.
 */
CpuReserve CpuReserve::KernThreadCpuReserve(Prio::Normal);

/* OnQuantaExpiration()  is called whenever the residual quanta of a
 * reserve goes to zero (i.e. when whenever the quanta expires).  When
 * a process hits the end of it's quanta, we recompute the reserve's
 * effective priority and re-queue the process at that priority.
 * 
 * The basic idea is that the
 * low level clock code will down-count the residual quanta.  When it
 * hits zero, it will call Thread::ShouldYield() on the current
 * thread.  The Yield() code will recompute priority for current
 * thread if appropriate and drop it to the back of the run queue at
 * that priority.
 */

void
CpuReserve::OnQuantaExpiration()
{
  /* dprintf(false, "Quanta expired on cpu reserve 0x%08x\n", this); */
  
  Thread::Current()->Preempt();

#if 0
  if (!Thread::Current()->CAN_PREEMPT()) {
    printf("CpuReserve::OnQuantaExpiration(): 0x%08x Quanta expires in NOPREEMPT, state %d.\n",
		   Thread::Current(), Thread::Current()->state); 
  }
#endif
  
  if (residDuration) {	/* reserve still active. */
    residQuanta = min(residDuration, quanta);
    residDuration -= quanta;
  }
  else {			/* not running under reserve. */
    if (active)
      Deplenish();
    
    residQuanta = quanta;
  }

  expired = false;
}

void
CpuReserve::AdjustCurPrio(int prio)
{
  curPrio = prio;
  
  Link *nextLink = threadChain.prev;
  
  while (nextLink) {
    Thread *t = Thread::ThreadFromCpuReserveLinkage(nextLink);
    nextLink = nextLink->next;

    /* Reposition the thread in the run queue: */
    t->Unlink();
    t->Wakeup();
  }
}

/* Note that both Deplenish() and Replenish() preserve ordering of
 * threads in the run queue!
 */
void
CpuReserve::Deplenish()
{
  /*  dprintf(false, "Deplenishing CpuReserve 0x%08x\n", this); */

  active = false;

  AdjustCurPrio(normPrio);
}

void
CpuReserve::Replenish()
{
  /* dprintf(false, "Replenishing CpuReserve 0x%08x\n", this); */

  /* If a thread under this reserve happens to be currently running,
   * it gets an extra boost via quanta extension.
   */
  if (period && duration) {
    active = true;
    residQuanta = quanta;
    residDuration = duration - quanta;
  
    AdjustCurPrio(rsrvPrio);

    uint64_t nextPeriod = SysTimer::Now() + period;

    reserveTimer.WakeupAtTick(nextPeriod, &CpuReserve::Replenish);
  }
  else {
    active = false;

    AdjustCurPrio(normPrio);
  }
  expired = false;
}

void
CpuReserve::Replenish(Timer* timer)
{
  CpuReserve &r = *((CpuReserve *) timer->client_ptr);

  r.Replenish();
}

CpuReserve::CpuReserve()
{
  start = 0ll;
  quanta = Machine::MillisecondsToTicks(DEFAULT_SCHED_QUANTA);
  duration = 0ll;
  period = 0ll;
  expired = false;

  residQuanta = quanta;
  residDuration = 0ll;

  rsrvPrio = Prio::Inactive;
  normPrio = Prio::Inactive;

  active = false;
  curPrio = normPrio;
  
  reserveTimer.client_ptr = this;
}

CpuReserve::CpuReserve(int prio)
{
  start = 0ll;
  quanta = Machine::MillisecondsToTicks(DEFAULT_SCHED_QUANTA);
  duration = 0ll;
  period = 0ll;
  expired = false;

  residQuanta = quanta;
  residDuration = 0ll;

  rsrvPrio = Prio::Inactive;
  normPrio = prio;

  active = false;
  curPrio = normPrio;
  
  reserveTimer.client_ptr = this;
}

void
CpuReserve::AddKernelThread(Thread *t)
{
  AddUserThread(t);
  assert (t->context);
  t->context->cpuReserve = this;
}

/* Reserve linkage not circular! */
void
CpuReserve::AddUserThread(Thread *t)
{
  Link& reserveLinkage = t->reserveLinkage;

#if 0
  if (t->IsUser())
    dprintf(true, "Add user thrd 0x%08x to rsrv 0x%08x\n", t,
		    this);
  else {
    assert (reserveLinkage.next == 0);
    assert (reserveLinkage.prev == 0);
  }
#endif
  
  reserveLinkage.Unlink();

  t->cpuReserve = this;
    
  reserveLinkage.next = threadChain.next;
  if (threadChain.next)
    threadChain.next->prev = &reserveLinkage;
  threadChain.next = &reserveLinkage;

  reserveLinkage.prev = &threadChain;
}

void
CpuReserve::AllocUserCpuReserves()
{
  CpuReserveTable = new (0) CpuReserve[MAX_CPU_RESERVE];

  for (int i = 0; i < STD_CPU_RESERVE; i++) {
    CpuReserveTable[i].normPrio = i;
    CpuReserveTable[i].AdjustCurPrio(i);
  }

  printf("Allocated CPU Reserves: 0x%x at 0x%08x\n",
		 sizeof(CpuReserve[MAX_CPU_RESERVE]), CpuReserveTable);
}

void
CpuReserve::Reset()
{
  if (quanta == 0)
    quanta = Machine::MillisecondsToTicks(DEFAULT_SCHED_QUANTA);
  if (duration && period) {
    if (start)
      reserveTimer.WakeupAtTick(start, Replenish);
    else			/* wake it up right now. */
      Replenish();
  }
  else {
    Deplenish();
  }
}

CpuReserve&
CpuReserve::GetReserve(const Key& k)
{
  if (k.IsType(KT_Sched))
    return CpuReserveTable[k.keyData];

  return InactiveReserve;
}