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author | Jeff Roberson <jeff@FreeBSD.org> | 2002-10-12 05:32:24 +0000 |
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committer | Jeff Roberson <jeff@FreeBSD.org> | 2002-10-12 05:32:24 +0000 |
commit | b43179fbe815b81e2d6bb729ffcb08e8f0a143da (patch) | |
tree | 69991942d3c51153d9210031e7380779edf05aaf /sys/kern/sched_4bsd.c | |
parent | bd26dcd10398fc7436ec5f3ee1a35ef5a7ae54dd (diff) | |
download | src-b43179fbe815b81e2d6bb729ffcb08e8f0a143da.tar.gz src-b43179fbe815b81e2d6bb729ffcb08e8f0a143da.zip |
- Create a new scheduler api that is defined in sys/sched.h
- Begin moving scheduler specific functionality into sched_4bsd.c
- Replace direct manipulation of scheduler data with hooks provided by the
new api.
- Remove KSE specific state modifications and single runq assumptions from
kern_switch.c
Reviewed by: -arch
Notes
Notes:
svn path=/head/; revision=104964
Diffstat (limited to 'sys/kern/sched_4bsd.c')
-rw-r--r-- | sys/kern/sched_4bsd.c | 635 |
1 files changed, 635 insertions, 0 deletions
diff --git a/sys/kern/sched_4bsd.c b/sys/kern/sched_4bsd.c new file mode 100644 index 000000000000..99d23aac0c3e --- /dev/null +++ b/sys/kern/sched_4bsd.c @@ -0,0 +1,635 @@ +/*- + * 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 <sys/param.h> +#include <sys/systm.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/sched.h> +#include <sys/smp.h> +#include <sys/sysctl.h> +#include <sys/sx.h> + + +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->ke_flags |= KEF_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, ""); + +/* 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(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. + */ +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_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) +{ + /* + * set priority of child to be that of parent. + * XXXKSE this needs redefining.. + */ + child->kg_estcpu = kg->kg_estcpu; +} + +void +sched_nice(struct ksegrp *kg, int nice) +{ + kg->kg_nice = nice; + resetpriority(kg); +} + +void +sched_prio(struct thread *td, u_char prio) +{ + td->td_priority = prio; + + if (TD_ON_RUNQ(td)) { + remrunqueue(td); + setrunqueue(td); + } +} + +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; + 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)) { + /* 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. + * (If bound LOANING can still occur). + */ + 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); + } +} |