diff options
Diffstat (limited to 'sys/kern/kern_synch.c')
| -rw-r--r-- | sys/kern/kern_synch.c | 970 |
1 files changed, 970 insertions, 0 deletions
diff --git a/sys/kern/kern_synch.c b/sys/kern/kern_synch.c new file mode 100644 index 0000000..6f9adad --- /dev/null +++ b/sys/kern/kern_synch.c @@ -0,0 +1,970 @@ +/*- + * 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 <sys/param.h> +#include <sys/systm.h> +#include <sys/condvar.h> +#include <sys/kernel.h> +#include <sys/ktr.h> +#include <sys/lock.h> +#include <sys/mutex.h> +#include <sys/proc.h> +#include <sys/resourcevar.h> +#include <sys/signalvar.h> +#include <sys/smp.h> +#include <sys/sx.h> +#include <sys/sysctl.h> +#include <sys/sysproto.h> +#include <sys/vmmeter.h> +#ifdef DDB +#include <ddb/ddb.h> +#endif +#ifdef KTRACE +#include <sys/uio.h> +#include <sys/ktrace.h> +#endif + +#include <machine/cpu.h> + +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. + */ + /* XXXKSE */ + /* if ((ke->ke_flags & KEF_ONRUNQ) == 0) */ + if (p->p_stat == SSLEEP || p->p_stat == SSTOP) { + ke->ke_slptime++; + } else { + ke->ke_slptime = 0; + awake = 1; + } + + /* + * 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_slptime > 1) { + 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 (awake == 0) { + kg->kg_slptime++; + } else { + kg->kg_slptime = 0; + } + kg->kg_estcpu = decay_cpu(loadfac, kg->kg_estcpu); + resetpriority(kg); + td = FIRST_THREAD_IN_PROC(p); + if (td->td_priority >= PUSER && + (p->p_sflag & PS_INMEM)) { + int changedqueue = + ((td->td_priority / RQ_PPQ) != + (kg->kg_user_pri / RQ_PPQ)); + + td->td_priority = kg->kg_user_pri; + FOREACH_KSE_IN_GROUP(kg, ke) { + if ((ke->ke_oncpu == NOCPU) && + (p->p_stat == SRUN) && /* XXXKSE */ + changedqueue) { + remrunqueue(ke->ke_thread); + setrunqueue(ke->ke_thread); + } + } + } + } /* end of ksegrp loop */ + mtx_unlock_spin(&sched_lock); + } /* end of process loop */ + sx_sunlock(&allproc_lock); + wakeup((caddr_t)&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(td) + register struct thread *td; +{ + register struct ksegrp *kg; + register unsigned int newcpu; + register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); + + if (td == NULL) + return; + kg = td->td_ksegrp; + 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(td->td_ksegrp); +} + +/* + * 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")); + mtx_lock_spin(&sched_lock); + if (cold || panicstr) { + /* + * After a panic, or 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->td_proc->p_stat == SRUN, ("msleep")); + + td->td_wchan = ident; + td->td_wmesg = wmesg; + td->td_kse->ke_slptime = 0; /* XXXKSE */ + td->td_ksegrp->kg_slptime = 0; + td->td_priority = priority & PRIMASK; + CTR5(KTR_PROC, "msleep: thread %p (pid %d, %s) on %s (%p)", + td, p->p_pid, p->p_comm, wmesg, ident); + TAILQ_INSERT_TAIL(&slpque[LOOKUP(ident)], td, td_slpq); + if (timo) + callout_reset(&td->td_slpcallout, timo, endtsleep, td); + /* + * We put ourselves on the sleep queue and start our timeout + * before calling cursig, as we could stop there, and a wakeup + * or a SIGCONT (or both) could occur while we were stopped. + * A SIGCONT would cause us to be marked as SSLEEP + * 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: proc %p (pid %d, %s)", p, + p->p_pid, p->p_comm); + td->td_flags |= TDF_SINTR; + mtx_unlock_spin(&sched_lock); + PROC_LOCK(p); + sig = cursig(p); + mtx_lock_spin(&sched_lock); + PROC_UNLOCK(p); + if (sig != 0) { + if (td->td_wchan != NULL) + unsleep(td); + } else if (td->td_wchan == NULL) + catch = 0; + } else + sig = 0; + if (td->td_wchan != NULL) { + td->td_proc->p_stat = SSLEEP; + p->p_stats->p_ru.ru_nvcsw++; + mi_switch(); + } + CTR3(KTR_PROC, "msleep resume: proc %p (pid %d, %s)", td, p->p_pid, + p->p_comm); + KASSERT(td->td_proc->p_stat == SRUN, ("running but not SRUN")); + 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->td_flags |= TDF_TIMEOUT; + p->p_stats->p_ru.ru_nivcsw++; + mi_switch(); + } + 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(p))) { + 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 PS_TIMEOUT flag is set, we lost the + * race and just need to put the process back on the runqueue. + */ + if ((td->td_flags & TDF_TIMEOUT) != 0) { + td->td_flags &= ~TDF_TIMEOUT; + setrunqueue(td); + } else if (td->td_wchan != NULL) { + if (td->td_proc->p_stat == SSLEEP) /* XXXKSE */ + setrunnable(td); + else + unsleep(td); + td->td_flags |= TDF_TIMEOUT; + } else { + td->td_flags |= TDF_TIMOFAIL; + } + mtx_unlock_spin(&sched_lock); +} + +/* + * Remove a process from its wait queue + */ +void +unsleep(struct thread *td) +{ + + mtx_lock_spin(&sched_lock); + if (td->td_wchan != NULL) { + TAILQ_REMOVE(&slpque[LOOKUP(td->td_wchan)], td, td_slpq); + td->td_wchan = NULL; + } + 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); + p = td->td_proc; + if (td->td_wchan == ident) { + TAILQ_REMOVE(qp, td, td_slpq); + td->td_wchan = NULL; + if (td->td_proc->p_stat == SSLEEP) { + /* OPTIMIZED EXPANSION OF setrunnable(p); */ + CTR3(KTR_PROC, "wakeup: thread %p (pid %d, %s)", + td, p->p_pid, p->p_comm); + if (td->td_ksegrp->kg_slptime > 1) + updatepri(td); + td->td_ksegrp->kg_slptime = 0; + td->td_kse->ke_slptime = 0; + td->td_proc->p_stat = SRUN; + if (p->p_sflag & PS_INMEM) { + setrunqueue(td); + maybe_resched(td); + } else { + p->p_sflag |= PS_SWAPINREQ; + wakeup((caddr_t)&proc0); + } + /* END INLINE EXPANSION */ + 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)]; +restart: + for (td = TAILQ_FIRST(qp); td != NULL; td = ntd) { + ntd = TAILQ_NEXT(td, td_slpq); + p = td->td_proc; + if (td->td_wchan == ident) { + TAILQ_REMOVE(qp, td, td_slpq); + td->td_wchan = NULL; + if (td->td_proc->p_stat == SSLEEP) { + /* OPTIMIZED EXPANSION OF setrunnable(p); */ + CTR3(KTR_PROC, "wakeup1: proc %p (pid %d, %s)", + p, p->p_pid, p->p_comm); + if (td->td_ksegrp->kg_slptime > 1) + updatepri(td); + td->td_ksegrp->kg_slptime = 0; + td->td_kse->ke_slptime = 0; + td->td_proc->p_stat = SRUN; + if (p->p_sflag & PS_INMEM) { + setrunqueue(td); + maybe_resched(td); + break; + } else { + p->p_sflag |= PS_SWAPINREQ; + wakeup((caddr_t)&proc0); + } + /* END INLINE EXPANSION */ + goto restart; + } + } + } + mtx_unlock_spin(&sched_lock); +} + +/* + * The machine independent parts of mi_switch(). + */ +void +mi_switch() +{ + struct bintime new_switchtime; + struct thread *td = curthread; /* XXX */ + register struct proc *p = td->td_proc; /* XXX */ +#if 0 + register struct rlimit *rlim; +#endif + u_int sched_nest; + + mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED); +#ifdef INVARIANTS + if (p->p_stat != SMTX && p->p_stat != SRUN) + mtx_assert(&Giant, MA_NOTOWNED); +#endif + + /* + * 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 + +#if 0 + /* + * Check if the process exceeds its cpu resource allocation. + * If over max, kill it. + * + * XXX drop sched_lock, pickup Giant + */ + if (p->p_stat != SZOMB && p->p_limit->p_cpulimit != RLIM_INFINITY && + p->p_runtime > p->p_limit->p_cpulimit) { + rlim = &p->p_rlimit[RLIMIT_CPU]; + if (p->p_runtime / (rlim_t)1000000 >= rlim->rlim_max) { + mtx_unlock_spin(&sched_lock); + PROC_LOCK(p); + killproc(p, "exceeded maximum CPU limit"); + mtx_lock_spin(&sched_lock); + PROC_UNLOCK(p); + } else { + mtx_unlock_spin(&sched_lock); + PROC_LOCK(p); + psignal(p, SIGXCPU); + mtx_lock_spin(&sched_lock); + PROC_UNLOCK(p); + if (rlim->rlim_cur < rlim->rlim_max) { + /* XXX: we should make a private copy */ + rlim->rlim_cur += 5; + } + } + } +#endif + + /* + * Pick a new current process and record its start time. + */ + cnt.v_swtch++; + PCPU_SET(switchtime, new_switchtime); + CTR3(KTR_PROC, "mi_switch: old proc %p (pid %d, %s)", p, p->p_pid, + p->p_comm); + sched_nest = sched_lock.mtx_recurse; + td->td_lastcpu = td->td_kse->ke_oncpu; + td->td_kse->ke_oncpu = NOCPU; + td->td_kse->ke_flags &= ~KEF_NEEDRESCHED; + cpu_switch(); + 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 proc %p (pid %d, %s)", p, p->p_pid, + p->p_comm); + if (PCPU_GET(switchtime.sec) == 0) + binuptime(PCPU_PTR(switchtime)); + PCPU_SET(switchticks, ticks); +} + +/* + * 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; + + mtx_lock_spin(&sched_lock); + switch (p->p_stat) { + case SZOMB: /* not a thread flag XXXKSE */ + panic("setrunnable(1)"); + } + switch (td->td_proc->p_stat) { + case 0: + case SRUN: + case SWAIT: + default: + panic("setrunnable(2)"); + case SSTOP: + case SSLEEP: /* e.g. when sending signals */ + if (td->td_flags & TDF_CVWAITQ) + cv_waitq_remove(td); + else + unsleep(td); + break; + + case SIDL: + break; + } + td->td_proc->p_stat = SRUN; + if (td->td_ksegrp->kg_slptime > 1) + updatepri(td); + td->td_ksegrp->kg_slptime = 0; + td->td_kse->ke_slptime = 0; + if ((p->p_sflag & PS_INMEM) == 0) { + p->p_sflag |= PS_SWAPINREQ; + wakeup((caddr_t)&proc0); + } else { + setrunqueue(td); + maybe_resched(td); + } + mtx_unlock_spin(&sched_lock); +} + +/* + * 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); + } + 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 ksegrp *kg; + + avg = &averunnable; + sx_slock(&allproc_lock); + nrun = 0; + FOREACH_PROC_IN_SYSTEM(p) { + FOREACH_KSEGRP_IN_PROC(p, kg) { + switch (p->p_stat) { + case SRUN: + if ((p->p_flag & P_NOLOAD) != 0) + goto nextproc; + /* FALLTHROUGH */ + case SIDL: + nrun++; + } +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 = td->td_kse; + struct ksegrp *kg = td->td_ksegrp; + + if (td) { + ke->ke_cpticks++; + kg->kg_estcpu = ESTCPULIM(kg->kg_estcpu + 1); + if ((kg->kg_estcpu % INVERSE_ESTCPU_WEIGHT) == 0) { + resetpriority(td->td_ksegrp); + if (td->td_priority >= PUSER) + td->td_priority = kg->kg_user_pri; + } + } else { + panic("schedclock"); + } +} + +/* + * 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; + setrunqueue(td); + kg->kg_proc->p_stats->p_ru.ru_nvcsw++; + mi_switch(); + mtx_unlock_spin(&sched_lock); + td->td_retval[0] = 0; + + return (0); +} + |
