621 lines
18 KiB
C
621 lines
18 KiB
C
/*-
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* Copyright (c) 1982, 1986, 1990, 1991, 1993
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* The Regents of the University of California. All rights reserved.
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* (c) UNIX System Laboratories, Inc.
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* All or some portions of this file are derived from material licensed
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* to the University of California by American Telephone and Telegraph
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* Co. or Unix System Laboratories, Inc. and are reproduced herein with
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* the permission of UNIX System Laboratories, Inc.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kernel.h>
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#include <sys/ktr.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/proc.h>
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#include <sys/resourcevar.h>
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#include <sys/sched.h>
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#include <sys/smp.h>
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#include <sys/sysctl.h>
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#include <sys/sx.h>
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static int sched_quantum; /* Roundrobin scheduling quantum in ticks. */
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#define SCHED_QUANTUM (hz / 10); /* Default sched quantum */
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static struct callout schedcpu_callout;
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static struct callout roundrobin_callout;
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static void roundrobin(void *arg);
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static void schedcpu(void *arg);
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static void sched_setup(void *dummy);
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static void maybe_resched(struct thread *td);
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static void updatepri(struct ksegrp *kg);
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static void resetpriority(struct ksegrp *kg);
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SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL)
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/*
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* Global run queue.
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*/
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static struct runq runq;
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SYSINIT(runq, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, runq_init, &runq)
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static int
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sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
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{
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int error, new_val;
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new_val = sched_quantum * tick;
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error = sysctl_handle_int(oidp, &new_val, 0, req);
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if (error != 0 || req->newptr == NULL)
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return (error);
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if (new_val < tick)
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return (EINVAL);
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sched_quantum = new_val / tick;
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hogticks = 2 * sched_quantum;
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return (0);
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}
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SYSCTL_PROC(_kern, OID_AUTO, quantum, CTLTYPE_INT|CTLFLAG_RW,
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0, sizeof sched_quantum, sysctl_kern_quantum, "I",
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"Roundrobin scheduling quantum in microseconds");
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/*
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* Arrange to reschedule if necessary, taking the priorities and
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* schedulers into account.
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*/
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static void
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maybe_resched(struct thread *td)
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{
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mtx_assert(&sched_lock, MA_OWNED);
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if (td->td_priority < curthread->td_priority)
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curthread->td_kse->ke_flags |= KEF_NEEDRESCHED;
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}
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/*
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* Force switch among equal priority processes every 100ms.
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* We don't actually need to force a context switch of the current process.
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* The act of firing the event triggers a context switch to softclock() and
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* then switching back out again which is equivalent to a preemption, thus
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* no further work is needed on the local CPU.
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*/
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/* ARGSUSED */
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static void
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roundrobin(void *arg)
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{
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#ifdef SMP
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mtx_lock_spin(&sched_lock);
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forward_roundrobin();
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mtx_unlock_spin(&sched_lock);
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#endif
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callout_reset(&roundrobin_callout, sched_quantum, roundrobin, NULL);
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}
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/*
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* Constants for digital decay and forget:
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* 90% of (p_estcpu) usage in 5 * loadav time
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* 95% of (p_pctcpu) usage in 60 seconds (load insensitive)
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* Note that, as ps(1) mentions, this can let percentages
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* total over 100% (I've seen 137.9% for 3 processes).
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*
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* Note that schedclock() updates p_estcpu and p_cpticks asynchronously.
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*
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* We wish to decay away 90% of p_estcpu in (5 * loadavg) seconds.
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* That is, the system wants to compute a value of decay such
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* that the following for loop:
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* for (i = 0; i < (5 * loadavg); i++)
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* p_estcpu *= decay;
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* will compute
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* p_estcpu *= 0.1;
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* for all values of loadavg:
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*
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* Mathematically this loop can be expressed by saying:
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* decay ** (5 * loadavg) ~= .1
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*
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* The system computes decay as:
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* decay = (2 * loadavg) / (2 * loadavg + 1)
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*
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* We wish to prove that the system's computation of decay
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* will always fulfill the equation:
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* decay ** (5 * loadavg) ~= .1
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*
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* If we compute b as:
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* b = 2 * loadavg
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* then
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* decay = b / (b + 1)
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*
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* We now need to prove two things:
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* 1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1)
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* 2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg)
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*
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* Facts:
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* For x close to zero, exp(x) =~ 1 + x, since
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* exp(x) = 0! + x**1/1! + x**2/2! + ... .
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* therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b.
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* For x close to zero, ln(1+x) =~ x, since
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* ln(1+x) = x - x**2/2 + x**3/3 - ... -1 < x < 1
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* therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1).
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* ln(.1) =~ -2.30
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*
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* Proof of (1):
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* Solve (factor)**(power) =~ .1 given power (5*loadav):
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* solving for factor,
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* ln(factor) =~ (-2.30/5*loadav), or
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* factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) =
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* exp(-1/b) =~ (b-1)/b =~ b/(b+1). QED
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*
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* Proof of (2):
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* Solve (factor)**(power) =~ .1 given factor == (b/(b+1)):
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* solving for power,
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* power*ln(b/(b+1)) =~ -2.30, or
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* power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav. QED
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*
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* Actual power values for the implemented algorithm are as follows:
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* loadav: 1 2 3 4
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* power: 5.68 10.32 14.94 19.55
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*/
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/* calculations for digital decay to forget 90% of usage in 5*loadav sec */
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#define loadfactor(loadav) (2 * (loadav))
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#define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE))
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/* decay 95% of `p_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */
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static fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */
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SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");
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/* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
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static int fscale __unused = FSCALE;
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SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
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/*
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* If `ccpu' is not equal to `exp(-1/20)' and you still want to use the
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* faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below
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* and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT).
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*
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* To estimate CCPU_SHIFT for exp(-1/20), the following formula was used:
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* 1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits).
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*
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* If you don't want to bother with the faster/more-accurate formula, you
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* can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate
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* (more general) method of calculating the %age of CPU used by a process.
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*/
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#define CCPU_SHIFT 11
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/*
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* Recompute process priorities, every hz ticks.
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* MP-safe, called without the Giant mutex.
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*/
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/* ARGSUSED */
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static void
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schedcpu(void *arg)
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{
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register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
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struct thread *td;
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struct proc *p;
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struct kse *ke;
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struct ksegrp *kg;
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int realstathz;
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int awake;
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realstathz = stathz ? stathz : hz;
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sx_slock(&allproc_lock);
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FOREACH_PROC_IN_SYSTEM(p) {
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mtx_lock_spin(&sched_lock);
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p->p_swtime++;
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FOREACH_KSEGRP_IN_PROC(p, kg) {
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awake = 0;
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FOREACH_KSE_IN_GROUP(kg, ke) {
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/*
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* Increment time in/out of memory and sleep
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* time (if sleeping). We ignore overflow;
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* with 16-bit int's (remember them?)
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* overflow takes 45 days.
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*/
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/*
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* The kse slptimes are not touched in wakeup
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* because the thread may not HAVE a KSE.
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*/
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if (ke->ke_state == KES_ONRUNQ) {
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awake = 1;
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ke->ke_flags &= ~KEF_DIDRUN;
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} else if ((ke->ke_state == KES_THREAD) &&
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(TD_IS_RUNNING(ke->ke_thread))) {
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awake = 1;
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/* Do not clear KEF_DIDRUN */
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} else if (ke->ke_flags & KEF_DIDRUN) {
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awake = 1;
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ke->ke_flags &= ~KEF_DIDRUN;
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}
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/*
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* pctcpu is only for ps?
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* Do it per kse.. and add them up at the end?
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* XXXKSE
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*/
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ke->ke_pctcpu
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= (ke->ke_pctcpu * ccpu) >> FSHIFT;
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/*
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* If the kse has been idle the entire second,
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* stop recalculating its priority until
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* it wakes up.
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*/
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if (ke->ke_cpticks == 0)
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continue;
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#if (FSHIFT >= CCPU_SHIFT)
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ke->ke_pctcpu += (realstathz == 100) ?
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((fixpt_t) ke->ke_cpticks) <<
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(FSHIFT - CCPU_SHIFT) :
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100 * (((fixpt_t) ke->ke_cpticks) <<
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(FSHIFT - CCPU_SHIFT)) / realstathz;
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#else
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ke->ke_pctcpu += ((FSCALE - ccpu) *
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(ke->ke_cpticks * FSCALE / realstathz)) >>
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FSHIFT;
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#endif
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ke->ke_cpticks = 0;
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} /* end of kse loop */
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/*
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* If there are ANY running threads in this KSEGRP,
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* then don't count it as sleeping.
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*/
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if (awake) {
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if (kg->kg_slptime > 1) {
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/*
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* In an ideal world, this should not
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* happen, because whoever woke us
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* up from the long sleep should have
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* unwound the slptime and reset our
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* priority before we run at the stale
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* priority. Should KASSERT at some
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* point when all the cases are fixed.
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*/
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updatepri(kg);
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}
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kg->kg_slptime = 0;
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} else {
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kg->kg_slptime++;
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}
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if (kg->kg_slptime > 1)
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continue;
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kg->kg_estcpu = decay_cpu(loadfac, kg->kg_estcpu);
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resetpriority(kg);
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FOREACH_THREAD_IN_GROUP(kg, td) {
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if (td->td_priority >= PUSER) {
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sched_prio(td, kg->kg_user_pri);
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}
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}
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} /* end of ksegrp loop */
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mtx_unlock_spin(&sched_lock);
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} /* end of process loop */
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sx_sunlock(&allproc_lock);
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wakeup(&lbolt);
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callout_reset(&schedcpu_callout, hz, schedcpu, NULL);
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}
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/*
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* Recalculate the priority of a process after it has slept for a while.
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* For all load averages >= 1 and max p_estcpu of 255, sleeping for at
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* least six times the loadfactor will decay p_estcpu to zero.
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*/
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static void
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updatepri(struct ksegrp *kg)
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{
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register unsigned int newcpu;
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register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
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newcpu = kg->kg_estcpu;
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if (kg->kg_slptime > 5 * loadfac)
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kg->kg_estcpu = 0;
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else {
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kg->kg_slptime--; /* the first time was done in schedcpu */
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while (newcpu && --kg->kg_slptime)
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newcpu = decay_cpu(loadfac, newcpu);
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kg->kg_estcpu = newcpu;
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}
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resetpriority(kg);
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}
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/*
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* Compute the priority of a process when running in user mode.
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* Arrange to reschedule if the resulting priority is better
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* than that of the current process.
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*/
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static void
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resetpriority(struct ksegrp *kg)
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{
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register unsigned int newpriority;
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struct thread *td;
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mtx_lock_spin(&sched_lock);
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if (kg->kg_pri_class == PRI_TIMESHARE) {
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newpriority = PUSER + kg->kg_estcpu / INVERSE_ESTCPU_WEIGHT +
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NICE_WEIGHT * (kg->kg_nice - PRIO_MIN);
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newpriority = min(max(newpriority, PRI_MIN_TIMESHARE),
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PRI_MAX_TIMESHARE);
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kg->kg_user_pri = newpriority;
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}
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FOREACH_THREAD_IN_GROUP(kg, td) {
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maybe_resched(td); /* XXXKSE silly */
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}
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mtx_unlock_spin(&sched_lock);
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}
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/* ARGSUSED */
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static void
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sched_setup(void *dummy)
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{
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if (sched_quantum == 0)
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sched_quantum = SCHED_QUANTUM;
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hogticks = 2 * sched_quantum;
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callout_init(&schedcpu_callout, 1);
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callout_init(&roundrobin_callout, 0);
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/* Kick off timeout driven events by calling first time. */
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roundrobin(NULL);
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schedcpu(NULL);
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}
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/* External interfaces start here */
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int
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sched_runnable(void)
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{
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return runq_check(&runq);
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}
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int
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sched_rr_interval(void)
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{
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if (sched_quantum == 0)
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sched_quantum = SCHED_QUANTUM;
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return (sched_quantum);
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}
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/*
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* We adjust the priority of the current process. The priority of
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* a process gets worse as it accumulates CPU time. The cpu usage
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* estimator (p_estcpu) is increased here. resetpriority() will
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* compute a different priority each time p_estcpu increases by
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* INVERSE_ESTCPU_WEIGHT
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* (until MAXPRI is reached). The cpu usage estimator ramps up
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* quite quickly when the process is running (linearly), and decays
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* away exponentially, at a rate which is proportionally slower when
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* the system is busy. The basic principle is that the system will
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* 90% forget that the process used a lot of CPU time in 5 * loadav
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* seconds. This causes the system to favor processes which haven't
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* run much recently, and to round-robin among other processes.
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*/
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void
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sched_clock(struct thread *td)
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{
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struct kse *ke;
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struct ksegrp *kg;
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KASSERT((td != NULL), ("schedclock: null thread pointer"));
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ke = td->td_kse;
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kg = td->td_ksegrp;
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ke->ke_cpticks++;
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kg->kg_estcpu = ESTCPULIM(kg->kg_estcpu + 1);
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if ((kg->kg_estcpu % INVERSE_ESTCPU_WEIGHT) == 0) {
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resetpriority(kg);
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if (td->td_priority >= PUSER)
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td->td_priority = kg->kg_user_pri;
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}
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}
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/*
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|
* charge childs scheduling cpu usage to parent.
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*
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* XXXKSE assume only one thread & kse & ksegrp keep estcpu in each ksegrp.
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* Charge it to the ksegrp that did the wait since process estcpu is sum of
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* all ksegrps, this is strictly as expected. Assume that the child process
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* aggregated all the estcpu into the 'built-in' ksegrp.
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*/
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void
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sched_exit(struct ksegrp *kg, struct ksegrp *child)
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{
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kg->kg_estcpu = ESTCPULIM(kg->kg_estcpu + child->kg_estcpu);
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}
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|
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void
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sched_fork(struct ksegrp *kg, struct ksegrp *child)
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|
{
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/*
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* set priority of child to be that of parent.
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|
* XXXKSE this needs redefining..
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*/
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child->kg_estcpu = kg->kg_estcpu;
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}
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|
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void
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sched_nice(struct ksegrp *kg, int nice)
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|
{
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kg->kg_nice = nice;
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resetpriority(kg);
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}
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|
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/*
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|
* Adjust the priority of a thread.
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|
* This may include moving the thread within the KSEGRP,
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* changing the assignment of a kse to the thread,
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* and moving a KSE in the system run queue.
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|
*/
|
|
void
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sched_prio(struct thread *td, u_char prio)
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|
{
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|
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if (TD_ON_RUNQ(td)) {
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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;
|
|
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);
|
|
}
|
|
}
|