/*- * 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. * * $FreeBSD$ */ #include #include #include #include #include #include #include #include #include #include #include #include /* * INVERSE_ESTCPU_WEIGHT is only suitable for statclock() frequencies in * the range 100-256 Hz (approximately). */ #define ESTCPULIM(e) \ min((e), INVERSE_ESTCPU_WEIGHT * (NICE_WEIGHT * (PRIO_MAX - PRIO_MIN) - \ RQ_PPQ) + INVERSE_ESTCPU_WEIGHT - 1) #define INVERSE_ESTCPU_WEIGHT 8 /* 1 / (priorities per estcpu level). */ #define NICE_WEIGHT 1 /* Priorities per nice level. */ struct ke_sched { int ske_cpticks; /* (j) Ticks of cpu time. */ }; struct ke_sched ke_sched; struct ke_sched *kse0_sched = &ke_sched; struct kg_sched *ksegrp0_sched = NULL; struct p_sched *proc0_sched = NULL; struct td_sched *thread0_sched = NULL; static int sched_quantum; /* Roundrobin scheduling quantum in ticks. */ #define SCHED_QUANTUM (hz / 10); /* Default sched quantum */ static struct callout schedcpu_callout; static struct callout roundrobin_callout; static void roundrobin(void *arg); static void schedcpu(void *arg); static void sched_setup(void *dummy); static void maybe_resched(struct thread *td); static void updatepri(struct ksegrp *kg); static void resetpriority(struct ksegrp *kg); SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL) /* * Global run queue. */ static struct runq runq; SYSINIT(runq, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, runq_init, &runq) 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. */ static void maybe_resched(struct thread *td) { mtx_assert(&sched_lock, MA_OWNED); if (td->td_priority < curthread->td_priority && curthread->td_kse) curthread->td_flags |= TDF_NEEDRESCHED; } /* * 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(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, ""); /* * 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(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_sched->ske_cpticks == 0) continue; #if (FSHIFT >= CCPU_SHIFT) ke->ke_pctcpu += (realstathz == 100) ? ((fixpt_t) ke->ke_sched->ske_cpticks) << (FSHIFT - CCPU_SHIFT) : 100 * (((fixpt_t) ke->ke_sched->ske_cpticks) << (FSHIFT - CCPU_SHIFT)) / realstathz; #else ke->ke_pctcpu += ((FSCALE - ccpu) * (ke->ke_sched->ske_cpticks * FSCALE / realstathz)) >> FSHIFT; #endif ke->ke_sched->ske_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) { if (td->td_priority >= PUSER) { sched_prio(td, kg->kg_user_pri); } } } /* end of ksegrp loop */ mtx_unlock_spin(&sched_lock); } /* end of process loop */ sx_sunlock(&allproc_lock); 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. */ static 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); } /* * 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. */ static void resetpriority(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); } /* ARGSUSED */ static void sched_setup(void *dummy) { if (sched_quantum == 0) sched_quantum = SCHED_QUANTUM; hogticks = 2 * sched_quantum; callout_init(&schedcpu_callout, 1); callout_init(&roundrobin_callout, 0); /* Kick off timeout driven events by calling first time. */ roundrobin(NULL); schedcpu(NULL); } /* External interfaces start here */ int sched_runnable(void) { return runq_check(&runq); } int sched_rr_interval(void) { if (sched_quantum == 0) sched_quantum = SCHED_QUANTUM; return (sched_quantum); } /* * 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 sched_clock(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_sched->ske_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; } } /* * charge childs scheduling cpu usage to parent. * * XXXKSE assume only one thread & kse & ksegrp keep estcpu in each ksegrp. * Charge it to the ksegrp that did the wait since process estcpu is sum of * all ksegrps, this is strictly as expected. Assume that the child process * aggregated all the estcpu into the 'built-in' ksegrp. */ void sched_exit(struct ksegrp *kg, struct ksegrp *child) { kg->kg_estcpu = ESTCPULIM(kg->kg_estcpu + child->kg_estcpu); } void sched_fork(struct ksegrp *kg, struct ksegrp *child) { struct kse *ke; /* * set priority of child to be that of parent. * XXXKSE this needs redefining.. */ child->kg_estcpu = kg->kg_estcpu; /* Set up scheduler specific data */ ke = FIRST_KSE_IN_KSEGRP(kg); ke->ke_sched->ske_cpticks = 0; } void sched_nice(struct ksegrp *kg, int nice) { kg->kg_nice = nice; resetpriority(kg); } /* * Adjust the priority of a thread. * This may include moving the thread within the KSEGRP, * changing the assignment of a kse to the thread, * and moving a KSE in the system run queue. */ void sched_prio(struct thread *td, u_char prio) { if (TD_ON_RUNQ(td)) { adjustrunqueue(td, prio); } else { td->td_priority = prio; } } void sched_sleep(struct thread *td, u_char prio) { td->td_ksegrp->kg_slptime = 0; td->td_priority = prio; } void sched_switchin(struct thread *td) { td->td_kse->ke_oncpu = PCPU_GET(cpuid); } void sched_switchout(struct thread *td) { struct kse *ke; struct proc *p; ke = td->td_kse; p = td->td_proc; KASSERT((ke->ke_state == KES_THREAD), ("mi_switch: kse state?")); td->td_lastcpu = ke->ke_oncpu; td->td_last_kse = ke; ke->ke_oncpu = NOCPU; td->td_flags &= ~TDF_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)) { /* Put us back on the run queue (kse and all). */ setrunqueue(td); } else if (p->p_flag & P_KSES) { /* * We will not be on the run queue. So we must be * sleeping or similar. As it's available, * someone else can use the KSE if they need it. */ kse_reassign(ke); } } void sched_wakeup(struct thread *td) { struct ksegrp *kg; kg = td->td_ksegrp; if (kg->kg_slptime > 1) updatepri(kg); kg->kg_slptime = 0; setrunqueue(td); maybe_resched(td); } void sched_add(struct kse *ke) { mtx_assert(&sched_lock, MA_OWNED); KASSERT((ke->ke_thread != NULL), ("runq_add: No thread on KSE")); KASSERT((ke->ke_thread->td_kse != NULL), ("runq_add: No KSE on thread")); KASSERT(ke->ke_state != KES_ONRUNQ, ("runq_add: kse %p (%s) already in run queue", ke, ke->ke_proc->p_comm)); KASSERT(ke->ke_proc->p_sflag & PS_INMEM, ("runq_add: process swapped out")); ke->ke_ksegrp->kg_runq_kses++; ke->ke_state = KES_ONRUNQ; runq_add(&runq, ke); } void sched_rem(struct kse *ke) { KASSERT(ke->ke_proc->p_sflag & PS_INMEM, ("runq_remove: process swapped out")); KASSERT((ke->ke_state == KES_ONRUNQ), ("KSE not on run queue")); mtx_assert(&sched_lock, MA_OWNED); runq_remove(&runq, ke); ke->ke_state = KES_THREAD; ke->ke_ksegrp->kg_runq_kses--; } struct kse * sched_choose(void) { struct kse *ke; ke = runq_choose(&runq); if (ke != NULL) { runq_remove(&runq, ke); ke->ke_state = KES_THREAD; KASSERT((ke->ke_thread != NULL), ("runq_choose: No thread on KSE")); KASSERT((ke->ke_thread->td_kse != NULL), ("runq_choose: No KSE on thread")); KASSERT(ke->ke_proc->p_sflag & PS_INMEM, ("runq_choose: process swapped out")); } return (ke); } void sched_userret(struct thread *td) { struct ksegrp *kg; /* * XXX we cheat slightly on the locking here to avoid locking in * the usual case. Setting td_priority here is essentially an * incomplete workaround for not setting it properly elsewhere. * Now that some interrupt handlers are threads, not setting it * properly elsewhere can clobber it in the window between setting * it here and returning to user mode, so don't waste time setting * it perfectly here. */ kg = td->td_ksegrp; if (td->td_priority != kg->kg_user_pri) { mtx_lock_spin(&sched_lock); td->td_priority = kg->kg_user_pri; mtx_unlock_spin(&sched_lock); } } int sched_sizeof_kse(void) { return (sizeof(struct kse) + sizeof(struct ke_sched)); } int sched_sizeof_ksegrp(void) { return (sizeof(struct ksegrp)); } int sched_sizeof_proc(void) { return (sizeof(struct proc)); } int sched_sizeof_thread(void) { return (sizeof(struct thread)); } fixpt_t sched_pctcpu(struct kse *ke) { return (ke->ke_pctcpu); }