/*- * Copyright (c) 1982, 1986, 1990, 1991, 1993 * The Regents of the University of California. All rights reserved. * (c) UNIX System Laboratories, Inc. * All or some portions of this file are derived from material licensed * to the University of California by American Telephone and Telegraph * Co. or Unix System Laboratories, Inc. and are reproduced herein with * the permission of UNIX System Laboratories, Inc. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)kern_synch.c 8.9 (Berkeley) 5/19/95 * $FreeBSD$ */ #include "opt_ddb.h" #include "opt_ktrace.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef DDB #include #endif #ifdef KTRACE #include #include #endif #include static void sched_setup(void *dummy); SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL) int hogticks; int lbolt; int sched_quantum; /* Roundrobin scheduling quantum in ticks. */ static struct callout loadav_callout; static struct callout schedcpu_callout; static struct callout roundrobin_callout; struct loadavg averunnable = { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */ /* * Constants for averages over 1, 5, and 15 minutes * when sampling at 5 second intervals. */ static fixpt_t cexp[3] = { 0.9200444146293232 * FSCALE, /* exp(-1/12) */ 0.9834714538216174 * FSCALE, /* exp(-1/60) */ 0.9944598480048967 * FSCALE, /* exp(-1/180) */ }; static void endtsleep(void *); static void loadav(void *arg); static void roundrobin(void *arg); static void schedcpu(void *arg); static int sysctl_kern_quantum(SYSCTL_HANDLER_ARGS) { int error, new_val; new_val = sched_quantum * tick; error = sysctl_handle_int(oidp, &new_val, 0, req); if (error != 0 || req->newptr == NULL) return (error); if (new_val < tick) return (EINVAL); sched_quantum = new_val / tick; hogticks = 2 * sched_quantum; return (0); } SYSCTL_PROC(_kern, OID_AUTO, quantum, CTLTYPE_INT|CTLFLAG_RW, 0, sizeof sched_quantum, sysctl_kern_quantum, "I", "Roundrobin scheduling quantum in microseconds"); /* * Arrange to reschedule if necessary, taking the priorities and * schedulers into account. */ void maybe_resched(struct thread *td) { mtx_assert(&sched_lock, MA_OWNED); if (td->td_priority < curthread->td_priority) curthread->td_kse->ke_flags |= KEF_NEEDRESCHED; } int roundrobin_interval(void) { return (sched_quantum); } /* * Force switch among equal priority processes every 100ms. * We don't actually need to force a context switch of the current process. * The act of firing the event triggers a context switch to softclock() and * then switching back out again which is equivalent to a preemption, thus * no further work is needed on the local CPU. */ /* ARGSUSED */ static void roundrobin(arg) void *arg; { #ifdef SMP mtx_lock_spin(&sched_lock); forward_roundrobin(); mtx_unlock_spin(&sched_lock); #endif callout_reset(&roundrobin_callout, sched_quantum, roundrobin, NULL); } /* * Constants for digital decay and forget: * 90% of (p_estcpu) usage in 5 * loadav time * 95% of (p_pctcpu) usage in 60 seconds (load insensitive) * Note that, as ps(1) mentions, this can let percentages * total over 100% (I've seen 137.9% for 3 processes). * * Note that schedclock() updates p_estcpu and p_cpticks asynchronously. * * We wish to decay away 90% of p_estcpu in (5 * loadavg) seconds. * That is, the system wants to compute a value of decay such * that the following for loop: * for (i = 0; i < (5 * loadavg); i++) * p_estcpu *= decay; * will compute * p_estcpu *= 0.1; * for all values of loadavg: * * Mathematically this loop can be expressed by saying: * decay ** (5 * loadavg) ~= .1 * * The system computes decay as: * decay = (2 * loadavg) / (2 * loadavg + 1) * * We wish to prove that the system's computation of decay * will always fulfill the equation: * decay ** (5 * loadavg) ~= .1 * * If we compute b as: * b = 2 * loadavg * then * decay = b / (b + 1) * * We now need to prove two things: * 1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1) * 2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg) * * Facts: * For x close to zero, exp(x) =~ 1 + x, since * exp(x) = 0! + x**1/1! + x**2/2! + ... . * therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b. * For x close to zero, ln(1+x) =~ x, since * ln(1+x) = x - x**2/2 + x**3/3 - ... -1 < x < 1 * therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1). * ln(.1) =~ -2.30 * * Proof of (1): * Solve (factor)**(power) =~ .1 given power (5*loadav): * solving for factor, * ln(factor) =~ (-2.30/5*loadav), or * factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) = * exp(-1/b) =~ (b-1)/b =~ b/(b+1). QED * * Proof of (2): * Solve (factor)**(power) =~ .1 given factor == (b/(b+1)): * solving for power, * power*ln(b/(b+1)) =~ -2.30, or * power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav. QED * * Actual power values for the implemented algorithm are as follows: * loadav: 1 2 3 4 * power: 5.68 10.32 14.94 19.55 */ /* calculations for digital decay to forget 90% of usage in 5*loadav sec */ #define loadfactor(loadav) (2 * (loadav)) #define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE)) /* decay 95% of `p_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */ static fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */ SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, ""); /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */ static int fscale __unused = FSCALE; SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, ""); /* * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT). * * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used: * 1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits). * * If you don't want to bother with the faster/more-accurate formula, you * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate * (more general) method of calculating the %age of CPU used by a process. */ #define CCPU_SHIFT 11 /* * Recompute process priorities, every hz ticks. * MP-safe, called without the Giant mutex. */ /* ARGSUSED */ static void schedcpu(arg) void *arg; { register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); struct thread *td; struct proc *p; struct kse *ke; struct ksegrp *kg; int realstathz; int awake; realstathz = stathz ? stathz : hz; sx_slock(&allproc_lock); FOREACH_PROC_IN_SYSTEM(p) { mtx_lock_spin(&sched_lock); p->p_swtime++; FOREACH_KSEGRP_IN_PROC(p, kg) { awake = 0; FOREACH_KSE_IN_GROUP(kg, ke) { /* * Increment time in/out of memory and sleep * time (if sleeping). We ignore overflow; * with 16-bit int's (remember them?) * overflow takes 45 days. */ /* * The kse slptimes are not touched in wakeup * because the thread may not HAVE a KSE. */ if (ke->ke_state == KES_ONRUNQ) { awake = 1; ke->ke_flags &= ~KEF_DIDRUN; } else if ((ke->ke_state == KES_THREAD) && (TD_IS_RUNNING(ke->ke_thread))) { awake = 1; /* Do not clear KEF_DIDRUN */ } else if (ke->ke_flags & KEF_DIDRUN) { awake = 1; ke->ke_flags &= ~KEF_DIDRUN; } /* * pctcpu is only for ps? * Do it per kse.. and add them up at the end? * XXXKSE */ ke->ke_pctcpu = (ke->ke_pctcpu * ccpu) >> FSHIFT; /* * If the kse has been idle the entire second, * stop recalculating its priority until * it wakes up. */ if (ke->ke_cpticks == 0) continue; #if (FSHIFT >= CCPU_SHIFT) ke->ke_pctcpu += (realstathz == 100) ? ((fixpt_t) ke->ke_cpticks) << (FSHIFT - CCPU_SHIFT) : 100 * (((fixpt_t) ke->ke_cpticks) << (FSHIFT - CCPU_SHIFT)) / realstathz; #else ke->ke_pctcpu += ((FSCALE - ccpu) * (ke->ke_cpticks * FSCALE / realstathz)) >> FSHIFT; #endif ke->ke_cpticks = 0; } /* end of kse loop */ /* * If there are ANY running threads in this KSEGRP, * then don't count it as sleeping. */ if (awake) { if (kg->kg_slptime > 1) { /* * In an ideal world, this should not * happen, because whoever woke us * up from the long sleep should have * unwound the slptime and reset our * priority before we run at the stale * priority. Should KASSERT at some * point when all the cases are fixed. */ updatepri(kg); } kg->kg_slptime = 0; } else { kg->kg_slptime++; } if (kg->kg_slptime > 1) continue; kg->kg_estcpu = decay_cpu(loadfac, kg->kg_estcpu); resetpriority(kg); FOREACH_THREAD_IN_GROUP(kg, td) { int changedqueue; if (td->td_priority >= PUSER) { /* * Only change the priority * of threads that are still at their * user priority. * XXXKSE This is problematic * as we may need to re-order * the threads on the KSEG list. */ changedqueue = ((td->td_priority / RQ_PPQ) != (kg->kg_user_pri / RQ_PPQ)); td->td_priority = kg->kg_user_pri; if (changedqueue && TD_ON_RUNQ(td)) { /* this could be optimised */ remrunqueue(td); td->td_priority = kg->kg_user_pri; setrunqueue(td); } else { td->td_priority = kg->kg_user_pri; } } } } /* end of ksegrp loop */ mtx_unlock_spin(&sched_lock); } /* end of process loop */ sx_sunlock(&allproc_lock); wakeup(&lbolt); callout_reset(&schedcpu_callout, hz, schedcpu, NULL); } /* * Recalculate the priority of a process after it has slept for a while. * For all load averages >= 1 and max p_estcpu of 255, sleeping for at * least six times the loadfactor will decay p_estcpu to zero. */ void updatepri(struct ksegrp *kg) { register unsigned int newcpu; register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); newcpu = kg->kg_estcpu; if (kg->kg_slptime > 5 * loadfac) kg->kg_estcpu = 0; else { kg->kg_slptime--; /* the first time was done in schedcpu */ while (newcpu && --kg->kg_slptime) newcpu = decay_cpu(loadfac, newcpu); kg->kg_estcpu = newcpu; } resetpriority(kg); } /* * We're only looking at 7 bits of the address; everything is * aligned to 4, lots of things are aligned to greater powers * of 2. Shift right by 8, i.e. drop the bottom 256 worth. */ #define TABLESIZE 128 static TAILQ_HEAD(slpquehead, thread) slpque[TABLESIZE]; #define LOOKUP(x) (((intptr_t)(x) >> 8) & (TABLESIZE - 1)) void sleepinit(void) { int i; sched_quantum = hz/10; hogticks = 2 * sched_quantum; for (i = 0; i < TABLESIZE; i++) TAILQ_INIT(&slpque[i]); } /* * General sleep call. Suspends the current process until a wakeup is * performed on the specified identifier. The process will then be made * runnable with the specified priority. Sleeps at most timo/hz seconds * (0 means no timeout). If pri includes PCATCH flag, signals are checked * before and after sleeping, else signals are not checked. Returns 0 if * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a * signal needs to be delivered, ERESTART is returned if the current system * call should be restarted if possible, and EINTR is returned if the system * call should be interrupted by the signal (return EINTR). * * The mutex argument is exited before the caller is suspended, and * entered before msleep returns. If priority includes the PDROP * flag the mutex is not entered before returning. */ int msleep(ident, mtx, priority, wmesg, timo) void *ident; struct mtx *mtx; int priority, timo; const char *wmesg; { struct thread *td = curthread; struct proc *p = td->td_proc; int sig, catch = priority & PCATCH; int rval = 0; WITNESS_SAVE_DECL(mtx); #ifdef KTRACE if (KTRPOINT(td, KTR_CSW)) ktrcsw(1, 0); #endif WITNESS_SLEEP(0, &mtx->mtx_object); KASSERT(timo != 0 || mtx_owned(&Giant) || mtx != NULL, ("sleeping without a mutex")); /* * If we are capable of async syscalls and there isn't already * another one ready to return, start a new thread * and queue it as ready to run. Note that there is danger here * because we need to make sure that we don't sleep allocating * the thread (recursion here might be bad). * Hence the TDF_INMSLEEP flag. */ if (p->p_flag & P_KSES) { /* Just don't bother if we are exiting and not the exiting thread. */ if ((p->p_flag & P_WEXIT) && catch && p->p_singlethread != td) return (EINTR); if (td->td_mailbox && (!(td->td_flags & TDF_INMSLEEP))) { /* * If we have no queued work to do, then * upcall to the UTS to see if it has more to do. * We don't need to upcall now, just make it and * queue it. */ mtx_lock_spin(&sched_lock); if (TAILQ_FIRST(&td->td_ksegrp->kg_runq) == NULL) { /* Don't recurse here! */ td->td_flags |= TDF_INMSLEEP; thread_schedule_upcall(td, td->td_kse); td->td_flags &= ~TDF_INMSLEEP; } mtx_unlock_spin(&sched_lock); } } mtx_lock_spin(&sched_lock); if (cold ) { /* * During autoconfiguration, just give interrupts * a chance, then just return. * Don't run any other procs or panic below, * in case this is the idle process and already asleep. */ if (mtx != NULL && priority & PDROP) mtx_unlock(mtx); mtx_unlock_spin(&sched_lock); return (0); } DROP_GIANT(); if (mtx != NULL) { mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED); WITNESS_SAVE(&mtx->mtx_object, mtx); mtx_unlock(mtx); if (priority & PDROP) mtx = NULL; } KASSERT(p != NULL, ("msleep1")); KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep")); CTR5(KTR_PROC, "msleep: thread %p (pid %d, %s) on %s (%p)", td, p->p_pid, p->p_comm, wmesg, ident); td->td_wchan = ident; td->td_wmesg = wmesg; td->td_ksegrp->kg_slptime = 0; td->td_priority = priority & PRIMASK; TAILQ_INSERT_TAIL(&slpque[LOOKUP(ident)], td, td_slpq); TD_SET_ON_SLEEPQ(td); if (timo) callout_reset(&td->td_slpcallout, timo, endtsleep, td); /* * We put ourselves on the sleep queue and start our timeout * before calling thread_suspend_check, as we could stop there, and * a wakeup or a SIGCONT (or both) could occur while we were stopped. * without resuming us, thus we must be ready for sleep * when cursig is called. If the wakeup happens while we're * stopped, td->td_wchan will be 0 upon return from cursig. */ if (catch) { CTR3(KTR_PROC, "msleep caught: thread %p (pid %d, %s)", td, p->p_pid, p->p_comm); td->td_flags |= TDF_SINTR; mtx_unlock_spin(&sched_lock); PROC_LOCK(p); sig = cursig(td); if (sig == 0 && thread_suspend_check(1)) sig = SIGSTOP; mtx_lock_spin(&sched_lock); PROC_UNLOCK(p); if (sig != 0) { if (TD_ON_SLEEPQ(td)) unsleep(td); } else if (!TD_ON_SLEEPQ(td)) catch = 0; } else sig = 0; if (TD_ON_SLEEPQ(td)) { p->p_stats->p_ru.ru_nvcsw++; TD_SET_SLEEPING(td); mi_switch(); } CTR3(KTR_PROC, "msleep resume: thread %p (pid %d, %s)", td, p->p_pid, p->p_comm); KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING")); td->td_flags &= ~TDF_SINTR; if (td->td_flags & TDF_TIMEOUT) { td->td_flags &= ~TDF_TIMEOUT; if (sig == 0) rval = EWOULDBLOCK; } else if (td->td_flags & TDF_TIMOFAIL) { td->td_flags &= ~TDF_TIMOFAIL; } else if (timo && callout_stop(&td->td_slpcallout) == 0) { /* * This isn't supposed to be pretty. If we are here, then * the endtsleep() callout is currently executing on another * CPU and is either spinning on the sched_lock or will be * soon. If we don't synchronize here, there is a chance * that this process may msleep() again before the callout * has a chance to run and the callout may end up waking up * the wrong msleep(). Yuck. */ TD_SET_SLEEPING(td); p->p_stats->p_ru.ru_nivcsw++; mi_switch(); td->td_flags &= ~TDF_TIMOFAIL; } mtx_unlock_spin(&sched_lock); if (rval == 0 && catch) { PROC_LOCK(p); /* XXX: shouldn't we always be calling cursig() */ if (sig != 0 || (sig = cursig(td))) { if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig)) rval = EINTR; else rval = ERESTART; } PROC_UNLOCK(p); } #ifdef KTRACE if (KTRPOINT(td, KTR_CSW)) ktrcsw(0, 0); #endif PICKUP_GIANT(); if (mtx != NULL) { mtx_lock(mtx); WITNESS_RESTORE(&mtx->mtx_object, mtx); } return (rval); } /* * Implement timeout for msleep() * * If process hasn't been awakened (wchan non-zero), * set timeout flag and undo the sleep. If proc * is stopped, just unsleep so it will remain stopped. * MP-safe, called without the Giant mutex. */ static void endtsleep(arg) void *arg; { register struct thread *td = arg; CTR3(KTR_PROC, "endtsleep: thread %p (pid %d, %s)", td, td->td_proc->p_pid, td->td_proc->p_comm); mtx_lock_spin(&sched_lock); /* * This is the other half of the synchronization with msleep() * described above. If the TDS_TIMEOUT flag is set, we lost the * race and just need to put the process back on the runqueue. */ if (TD_ON_SLEEPQ(td)) { TAILQ_REMOVE(&slpque[LOOKUP(td->td_wchan)], td, td_slpq); TD_CLR_ON_SLEEPQ(td); td->td_flags |= TDF_TIMEOUT; } else { td->td_flags |= TDF_TIMOFAIL; } TD_CLR_SLEEPING(td); setrunnable(td); mtx_unlock_spin(&sched_lock); } /* * Abort a thread, as if an interrupt had occured. Only abort * interruptable waits (unfortunatly it isn't only safe to abort others). * This is about identical to cv_abort(). * Think about merging them? * Also, whatever the signal code does... */ void abortsleep(struct thread *td) { mtx_assert(&sched_lock, MA_OWNED); /* * If the TDF_TIMEOUT flag is set, just leave. A * timeout is scheduled anyhow. */ if ((td->td_flags & (TDF_TIMEOUT | TDF_SINTR)) == TDF_SINTR) { if (TD_ON_SLEEPQ(td)) { unsleep(td); TD_CLR_SLEEPING(td); setrunnable(td); } } } /* * Remove a process from its wait queue */ void unsleep(struct thread *td) { mtx_lock_spin(&sched_lock); if (TD_ON_SLEEPQ(td)) { TAILQ_REMOVE(&slpque[LOOKUP(td->td_wchan)], td, td_slpq); TD_CLR_ON_SLEEPQ(td); } mtx_unlock_spin(&sched_lock); } /* * Make all processes sleeping on the specified identifier runnable. */ void wakeup(ident) register void *ident; { register struct slpquehead *qp; register struct thread *td; struct thread *ntd; struct proc *p; mtx_lock_spin(&sched_lock); qp = &slpque[LOOKUP(ident)]; restart: for (td = TAILQ_FIRST(qp); td != NULL; td = ntd) { ntd = TAILQ_NEXT(td, td_slpq); if (td->td_wchan == ident) { unsleep(td); TD_CLR_SLEEPING(td); setrunnable(td); p = td->td_proc; CTR3(KTR_PROC,"wakeup: thread %p (pid %d, %s)", td, p->p_pid, p->p_comm); goto restart; } } mtx_unlock_spin(&sched_lock); } /* * Make a process sleeping on the specified identifier runnable. * May wake more than one process if a target process is currently * swapped out. */ void wakeup_one(ident) register void *ident; { register struct slpquehead *qp; register struct thread *td; register struct proc *p; struct thread *ntd; mtx_lock_spin(&sched_lock); qp = &slpque[LOOKUP(ident)]; for (td = TAILQ_FIRST(qp); td != NULL; td = ntd) { ntd = TAILQ_NEXT(td, td_slpq); if (td->td_wchan == ident) { unsleep(td); TD_CLR_SLEEPING(td); setrunnable(td); p = td->td_proc; CTR3(KTR_PROC,"wakeup1: thread %p (pid %d, %s)", td, p->p_pid, p->p_comm); break; } } mtx_unlock_spin(&sched_lock); } /* * The machine independent parts of mi_switch(). */ void mi_switch(void) { struct bintime new_switchtime; struct thread *td = curthread; /* XXX */ struct proc *p = td->td_proc; /* XXX */ struct kse *ke = td->td_kse; u_int sched_nest; mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED); KASSERT((ke->ke_state == KES_THREAD), ("mi_switch: kse state?")); KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code")); #ifdef INVARIANTS if (!TD_ON_MUTEX(td) && !TD_ON_RUNQ(td) && !TD_IS_RUNNING(td)) mtx_assert(&Giant, MA_NOTOWNED); #endif KASSERT(td->td_critnest == 1, ("mi_switch: switch in a critical section")); /* * Compute the amount of time during which the current * process was running, and add that to its total so far. */ binuptime(&new_switchtime); bintime_add(&p->p_runtime, &new_switchtime); bintime_sub(&p->p_runtime, PCPU_PTR(switchtime)); #ifdef DDB /* * Don't perform context switches from the debugger. */ if (db_active) { mtx_unlock_spin(&sched_lock); db_error("Context switches not allowed in the debugger."); } #endif /* * Check if the process exceeds its cpu resource allocation. */ if (p->p_state != PRS_ZOMBIE && p->p_limit->p_cpulimit != RLIM_INFINITY && p->p_runtime.sec > p->p_limit->p_cpulimit) p->p_sflag |= PS_XCPU; /* * Finish up stats for outgoing thread. */ cnt.v_swtch++; PCPU_SET(switchtime, new_switchtime); CTR3(KTR_PROC, "mi_switch: old thread %p (pid %d, %s)", td, p->p_pid, p->p_comm); sched_nest = sched_lock.mtx_recurse; td->td_lastcpu = ke->ke_oncpu; ke->ke_oncpu = NOCPU; ke->ke_flags &= ~KEF_NEEDRESCHED; /* * At the last moment, if this thread is still marked RUNNING, * then put it back on the run queue as it has not been suspended * or stopped or any thing else similar. */ if (TD_IS_RUNNING(td)) { KASSERT(((ke->ke_flags & KEF_IDLEKSE) == 0), ("Idle thread in mi_switch with wrong state")); /* Put us back on the run queue (kse and all). */ setrunqueue(td); } else if (td->td_flags & TDF_UNBOUND) { /* * We will not be on the run queue. So we must be * sleeping or similar. If it's available, * someone else can use the KSE if they need it. * XXXKSE KSE loaning will change this. */ td->td_kse = NULL; kse_reassign(ke); } else if (p->p_flag & P_KSES) { KASSERT(((ke->ke_bound == NULL) || (ke->ke_bound == td)), ("mi_switch: bad bound state")); ke->ke_bound = td; kse_reassign(ke); } cpu_switch(); /* SHAZAM!!*/ /* * Start setting up stats etc. for the incoming thread. * Similar code in fork_exit() is returned to by cpu_switch() * in the case of a new thread/process. */ td->td_kse->ke_oncpu = PCPU_GET(cpuid); sched_lock.mtx_recurse = sched_nest; sched_lock.mtx_lock = (uintptr_t)td; CTR3(KTR_PROC, "mi_switch: new thread %p (pid %d, %s)", td, p->p_pid, p->p_comm); if (PCPU_GET(switchtime.sec) == 0) binuptime(PCPU_PTR(switchtime)); PCPU_SET(switchticks, ticks); /* * Call the switchin function while still holding the scheduler lock * (used by the idlezero code and the general page-zeroing code) */ if (td->td_switchin) td->td_switchin(); } /* * Change process state to be runnable, * placing it on the run queue if it is in memory, * and awakening the swapper if it isn't in memory. */ void setrunnable(struct thread *td) { struct proc *p = td->td_proc; struct ksegrp *kg; mtx_assert(&sched_lock, MA_OWNED); switch (p->p_state) { case PRS_ZOMBIE: panic("setrunnable(1)"); default: break; } switch (td->td_state) { case TDS_RUNNING: case TDS_RUNQ: return; case TDS_INHIBITED: /* * If we are only inhibited because we are swapped out * then arange to swap in this process. Otherwise just return. */ if (td->td_inhibitors != TDI_SWAPPED) return; case TDS_CAN_RUN: break; default: printf("state is 0x%x", td->td_state); panic("setrunnable(2)"); } if ((p->p_sflag & PS_INMEM) == 0) { if ((p->p_sflag & PS_SWAPPINGIN) == 0) { p->p_sflag |= PS_SWAPINREQ; wakeup(&proc0); } } else { kg = td->td_ksegrp; if (kg->kg_slptime > 1) updatepri(kg); kg->kg_slptime = 0; setrunqueue(td); maybe_resched(td); } } /* * Compute the priority of a process when running in user mode. * Arrange to reschedule if the resulting priority is better * than that of the current process. */ void resetpriority(kg) register struct ksegrp *kg; { register unsigned int newpriority; struct thread *td; mtx_lock_spin(&sched_lock); if (kg->kg_pri_class == PRI_TIMESHARE) { newpriority = PUSER + kg->kg_estcpu / INVERSE_ESTCPU_WEIGHT + NICE_WEIGHT * (kg->kg_nice - PRIO_MIN); newpriority = min(max(newpriority, PRI_MIN_TIMESHARE), PRI_MAX_TIMESHARE); kg->kg_user_pri = newpriority; } FOREACH_THREAD_IN_GROUP(kg, td) { maybe_resched(td); /* XXXKSE silly */ } mtx_unlock_spin(&sched_lock); } /* * Compute a tenex style load average of a quantity on * 1, 5 and 15 minute intervals. * XXXKSE Needs complete rewrite when correct info is available. * Completely Bogus.. only works with 1:1 (but compiles ok now :-) */ static void loadav(void *arg) { int i, nrun; struct loadavg *avg; struct proc *p; struct thread *td; avg = &averunnable; sx_slock(&allproc_lock); nrun = 0; FOREACH_PROC_IN_SYSTEM(p) { FOREACH_THREAD_IN_PROC(p, td) { switch (td->td_state) { case TDS_RUNQ: case TDS_RUNNING: if ((p->p_flag & P_NOLOAD) != 0) goto nextproc; nrun++; /* XXXKSE */ default: break; } nextproc: continue; } } sx_sunlock(&allproc_lock); for (i = 0; i < 3; i++) avg->ldavg[i] = (cexp[i] * avg->ldavg[i] + nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT; /* * Schedule the next update to occur after 5 seconds, but add a * random variation to avoid synchronisation with processes that * run at regular intervals. */ callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)), loadav, NULL); } /* ARGSUSED */ static void sched_setup(dummy) void *dummy; { callout_init(&schedcpu_callout, 1); callout_init(&roundrobin_callout, 0); callout_init(&loadav_callout, 0); /* Kick off timeout driven events by calling first time. */ roundrobin(NULL); schedcpu(NULL); loadav(NULL); } /* * We adjust the priority of the current process. The priority of * a process gets worse as it accumulates CPU time. The cpu usage * estimator (p_estcpu) is increased here. resetpriority() will * compute a different priority each time p_estcpu increases by * INVERSE_ESTCPU_WEIGHT * (until MAXPRI is reached). The cpu usage estimator ramps up * quite quickly when the process is running (linearly), and decays * away exponentially, at a rate which is proportionally slower when * the system is busy. The basic principle is that the system will * 90% forget that the process used a lot of CPU time in 5 * loadav * seconds. This causes the system to favor processes which haven't * run much recently, and to round-robin among other processes. */ void schedclock(td) struct thread *td; { struct kse *ke; struct ksegrp *kg; KASSERT((td != NULL), ("schedclock: null thread pointer")); ke = td->td_kse; kg = td->td_ksegrp; ke->ke_cpticks++; kg->kg_estcpu = ESTCPULIM(kg->kg_estcpu + 1); if ((kg->kg_estcpu % INVERSE_ESTCPU_WEIGHT) == 0) { resetpriority(kg); if (td->td_priority >= PUSER) td->td_priority = kg->kg_user_pri; } } /* * General purpose yield system call */ int yield(struct thread *td, struct yield_args *uap) { struct ksegrp *kg = td->td_ksegrp; mtx_assert(&Giant, MA_NOTOWNED); mtx_lock_spin(&sched_lock); td->td_priority = PRI_MAX_TIMESHARE; kg->kg_proc->p_stats->p_ru.ru_nvcsw++; mi_switch(); mtx_unlock_spin(&sched_lock); td->td_retval[0] = 0; return (0); }