freebsd-skq/sys/kern/sched_4bsd.c
Julian Elischer 93a7aa79d6 Add code to ddb to allow backtracing an arbitrary thread.
(show thread {address})

Remove the IDLE kse state and replace it with a change in
the way threads sahre KSEs. Every KSE now has a thread, which is
considered its "owner" however a KSE may also be lent to other
threads in the same group to allow completion of in-kernel work.
n this case the owner remains the same and the KSE will revert to the
owner when the other work has been completed.

All creations of upcalls etc. is now done from
kse_reassign() which in turn is called from mi_switch or
thread_exit(). This means that special code can be removed from
msleep() and cv_wait().

kse_release() does not leave a KSE with no thread any more but
converts the existing thread into teh KSE's owner, and sets it up
for doing an upcall. It is just inhibitted from being scheduled until
there is some reason to do an upcall.

Remove all trace of the kse_idle queue since it is no-longer needed.
"Idle" KSEs are now on the loanable queue.
2002-12-28 01:23:07 +00:00

657 lines
18 KiB
C

/*-
* 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>
/*
* 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 *kse0_sched = NULL;
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_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, "");
/*
* 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) {
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_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);
}
/*
* 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;
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);
}
}
int
sched_sizeof_kse(void)
{
return (sizeof(struct kse));
}
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);
}