ref: 7628681f83b663609eace87a50f8fbf68c31f40b
dir: /sys/src/9/port/edf.c/
/* EDF scheduling */
#include <u.h>
#include "../port/lib.h"
#include "mem.h"
#include "dat.h"
#include "fns.h"
#include "../port/error.h"
#include "../port/edf.h"
#include <trace.h>
/* debugging */
enum {
Dontprint = 1,
};
#define DPRINT if(Dontprint){}else print
static long now; /* Low order 32 bits of time in µs */
extern ulong delayedscheds;
extern Schedq runq[Nrq];
extern int nrdy;
extern ulong runvec;
/* Statistics stuff */
ulong nilcount;
ulong scheds;
ulong edfnrun;
int misseddeadlines;
/* Edfschedlock protects modification of admission params */
int edfinited;
QLock edfschedlock;
static Lock thelock;
enum{
Dl, /* Invariant for schedulability test: Dl < Rl */
Rl,
};
static char *testschedulability(Proc*);
static Proc *qschedulability;
enum {
Onemicrosecond = 1,
Onemillisecond = 1000,
Onesecond = 1000000,
OneRound = Onemillisecond/2,
};
static int
timeconv(Fmt *f)
{
char buf[128], *sign;
vlong t;
buf[0] = 0;
switch(f->r) {
case 'U':
t = va_arg(f->args, uvlong);
break;
case 't': /* vlong in nanoseconds */
t = va_arg(f->args, long);
break;
default:
return fmtstrcpy(f, "(timeconv)");
}
if (t < 0) {
sign = "-";
t = -t;
}
else
sign = "";
if (t > Onesecond){
t += OneRound;
sprint(buf, "%s%d.%.3ds", sign, (int)(t / Onesecond),
(int)(t % Onesecond)/Onemillisecond);
}else if (t > Onemillisecond)
sprint(buf, "%s%d.%.3dms", sign, (int)(t / Onemillisecond),
(int)(t % Onemillisecond));
else
sprint(buf, "%s%dµs", sign, (int)t);
return fmtstrcpy(f, buf);
}
long edfcycles;
Edf*
edflock(Proc *p)
{
Edf *e;
if (p->edf == nil)
return nil;
ilock(&thelock);
if((e = p->edf) && (e->flags & Admitted)){
thelock.pc = getcallerpc(&p);
#ifdef EDFCYCLES
edfcycles -= lcycles();
#endif
now = µs();
return e;
}
iunlock(&thelock);
return nil;
}
void
edfunlock(void)
{
#ifdef EDFCYCLES
edfcycles += lcycles();
#endif
edfnrun++;
iunlock(&thelock);
}
void
edfinit(Proc*p)
{
if(!edfinited){
fmtinstall('t', timeconv);
edfinited++;
}
now = µs();
DPRINT("%lud edfinit %lud[%s]\n", now, p->pid, statename[p->state]);
p->edf = malloc(sizeof(Edf));
if(p->edf == nil)
error(Enomem);
return;
}
static void
deadlineintr(Ureg*, Timer *t)
{
/* Proc reached deadline */
Proc *p;
void (*pt)(Proc*, int, vlong);
if(panicking || active.exiting)
return;
p = t->ta;
now = µs();
DPRINT("%lud deadlineintr %lud[%s]\n", now, p->pid, statename[p->state]);
/* If we're interrupting something other than the proc pointed to by t->a,
* we've already achieved recheduling, so we need not do anything
* Otherwise, we must cause a reschedule, but if we call sched()
* here directly, the timer interrupt routine will not finish its business
* Instead, we cause the resched to happen when the interrupted proc
* returns to user space
*/
if(p == up){
if(up->trace && (pt = proctrace))
pt(up, SInts, 0);
up->delaysched++;
delayedscheds++;
}
}
static void
release(Proc *p)
{
/* Called with edflock held */
Edf *e;
void (*pt)(Proc*, int, vlong);
long n;
vlong nowns;
e = p->edf;
e->flags &= ~Yield;
if(e->d - now < 0){
e->periods++;
e->r = now;
if((e->flags & Sporadic) == 0){
/*
* Non sporadic processes stay true to their period;
* calculate next release time.
* Second test limits duration of while loop.
*/
if((n = now - e->t) > 0){
if(n < e->T)
e->t += e->T;
else
e->t = now + e->T - (n % e->T);
}
}else{
/* Sporadic processes may not be released earlier than
* one period after this release
*/
e->t = e->r + e->T;
}
e->d = e->r + e->D;
e->S = e->C;
DPRINT("%lud release %lud[%s], r=%lud, d=%lud, t=%lud, S=%lud\n",
now, p->pid, statename[p->state], e->r, e->d, e->t, e->S);
if(pt = proctrace){
nowns = todget(nil);
pt(p, SRelease, nowns);
pt(p, SDeadline, nowns + 1000LL*e->D);
}
}else{
DPRINT("%lud release %lud[%s], too late t=%lud, called from %#p\n",
now, p->pid, statename[p->state], e->t, getcallerpc(&p));
}
}
static void
releaseintr(Ureg *u, Timer *t)
{
Proc *p;
if(panicking || active.exiting)
return;
p = t->ta;
if((edflock(p)) == nil)
return;
DPRINT("%lud releaseintr %lud[%s]\n", now, p->pid, statename[p->state]);
switch(p->state){
default:
edfunlock();
return;
case Ready:
/* remove proc from current runq */
if(dequeueproc(&runq[p->priority], p) != p){
DPRINT("releaseintr: can't find proc or lock race\n");
release(p); /* It'll start best effort */
edfunlock();
return;
}
/* fall through */
case Waitrelease:
p->state = Scheding;
release(p);
edfunlock();
ready(p);
if(up){
up->delaysched++;
delayedscheds++;
}
return;
case Running:
release(p);
edfrun(p, 1);
break;
case Wakeme:
release(p);
edfunlock();
twakeup(u, t);
if(up){
up->delaysched++;
delayedscheds++;
}
return;
}
edfunlock();
}
void
edfrecord(Proc *p)
{
long used;
Edf *e;
void (*pt)(Proc*, int, vlong);
if((e = edflock(p)) == nil)
return;
used = now - e->s;
if(e->d - now <= 0)
e->edfused += used;
else
e->extraused += used;
if(e->S > 0){
if(e->S <= used){
if(pt = proctrace)
pt(p, SSlice, 0);
DPRINT("%lud edfrecord slice used up\n", now);
e->d = now;
e->S = 0;
}else
e->S -= used;
}
e->s = now;
edfunlock();
}
void
edfrun(Proc *p, int edfpri)
{
Edf *e;
void (*pt)(Proc*, int, vlong);
long tns;
e = p->edf;
/* Called with edflock held */
if(edfpri){
tns = e->d - now;
if(tns <= 0 || e->S == 0){
/* Deadline reached or resources exhausted,
* deschedule forthwith
*/
p->delaysched++;
delayedscheds++;
e->s = now;
return;
}
if(e->S < tns)
tns = e->S;
if(tns < 20)
tns = 20;
e->tns = 1000LL * tns; /* µs to ns */
if(e->tt == nil || e->tf != deadlineintr){
DPRINT("%lud edfrun, deadline=%lud\n", now, tns);
}else{
DPRINT("v");
}
if(p->trace && (pt = proctrace))
pt(p, SInte, todget(nil) + e->tns);
e->tmode = Trelative;
e->tf = deadlineintr;
e->ta = p;
timeradd(e);
}else{
DPRINT("<");
}
e->s = now;
}
char *
edfadmit(Proc *p)
{
char *err;
Edf *e;
int i;
Proc *r;
void (*pt)(Proc*, int, vlong);
long tns;
e = p->edf;
if (e->flags & Admitted)
return "task state"; /* should never happen */
/* simple sanity checks */
if (e->T == 0)
return "T not set";
if (e->C == 0)
return "C not set";
if (e->D > e->T)
return "D > T";
if (e->D == 0) /* if D is not set, set it to T */
e->D = e->T;
if (e->C > e->D)
return "C > D";
qlock(&edfschedlock);
if (err = testschedulability(p)){
qunlock(&edfschedlock);
return err;
}
e->flags |= Admitted;
edflock(p);
if(p->trace && (pt = proctrace))
pt(p, SAdmit, 0);
/* Look for another proc with the same period to synchronize to */
for(i=0; (r = proctab(i)) != nil; i++) {
if(r->state <= New || r == p)
continue;
if(r->edf == nil || (r->edf->flags & Admitted) == 0)
continue;
if(r->edf->T == e->T)
break;
}
if(r == nil){
/* Can't synchronize to another proc, release now */
e->t = now;
e->d = 0;
release(p);
if (p == up){
DPRINT("%lud edfadmit self %lud[%s], release now: r=%lud d=%lud t=%lud\n",
now, p->pid, statename[p->state], e->r, e->d, e->t);
/* We're already running */
edfrun(p, 1);
}else{
/* We're releasing another proc */
DPRINT("%lud edfadmit other %lud[%s], release now: r=%lud d=%lud t=%lud\n",
now, p->pid, statename[p->state], e->r, e->d, e->t);
p->ta = p;
edfunlock();
qunlock(&edfschedlock);
releaseintr(nil, p);
return nil;
}
}else{
/* Release in synch to something else */
e->t = r->edf->t;
if (p == up){
DPRINT("%lud edfadmit self %lud[%s], release at %lud\n",
now, p->pid, statename[p->state], e->t);
edfunlock();
qunlock(&edfschedlock);
return nil;
}else{
DPRINT("%lud edfadmit other %lud[%s], release at %lud\n",
now, p->pid, statename[p->state], e->t);
if(e->tt == nil){
tns = e->t - now;
if(tns < 20)
tns = 20;
e->tns = 1000LL * tns;
e->tmode = Trelative;
e->tf = releaseintr;
e->ta = p;
timeradd(e);
}
}
}
edfunlock();
qunlock(&edfschedlock);
return nil;
}
void
edfstop(Proc *p)
{
Edf *e;
void (*pt)(Proc*, int, vlong);
if(e = edflock(p)){
DPRINT("%lud edfstop %lud[%s]\n", now, p->pid, statename[p->state]);
if(p->trace && (pt = proctrace))
pt(p, SExpel, 0);
e->flags &= ~Admitted;
timerdel(e);
edfunlock();
}
}
static int
yfn(void *)
{
now = µs();
return up->trend == nil || now - up->edf->r >= 0;
}
void
edfyield(void)
{
/* sleep until next release */
Edf *e;
void (*pt)(Proc*, int, vlong);
long n;
if((e = edflock(up)) == nil)
return;
if(up->trace && (pt = proctrace))
pt(up, SYield, 0);
if((n = now - e->t) > 0){
if(n < e->T)
e->t += e->T;
else
e->t = now + e->T - (n % e->T);
}
e->r = e->t;
e->flags |= Yield;
e->d = now;
n = e->t - now;
if(n < 20)
n = 20;
up->tns = 1000LL * n;
up->tmode = Trelative;
up->tf = releaseintr;
up->ta = up;
up->trend = &up->sleep;
timeradd(up);
edfunlock();
if(waserror()){
up->trend = nil;
timerdel(up);
nexterror();
}
sleep(&up->sleep, yfn, nil);
up->trend = nil;
timerdel(up);
poperror();
}
int
edfready(Proc *p)
{
Edf *e;
long n;
if((e = edflock(p)) == nil)
return 0;
if(e->d - now <= 0){
/* past deadline, arrange for next release */
if((e->flags & Sporadic) == 0){
/*
* Non sporadic processes stay true to their period;
* calculate next release time.
*/
if((n = now - e->t) > 0){
if(n < e->T)
e->t += e->T;
else
e->t = now + e->T - (n % e->T);
}
}
if(now - e->t < 0){
/* Next release is in the future, schedule it */
if(e->tt == nil || e->tf != releaseintr){
n = e->t - now;
if(n < 20)
n = 20;
e->tns = 1000LL * n;
e->tmode = Trelative;
e->tf = releaseintr;
e->ta = p;
timeradd(e);
DPRINT("%lud edfready %lud[%s], release=%lud\n",
now, p->pid, statename[p->state], e->t);
}
if(p->state == Running && (e->flags & (Yield|Yieldonblock)) == 0 && (e->flags & Extratime)){
/* If we were running, we've overrun our CPU allocation
* or missed the deadline, continue running best-effort at low priority
* Otherwise we were blocked. If we don't yield on block, we continue
* best effort
*/
DPRINT(">");
p->basepri = PriExtra;
p->fixedpri = 1;
edfunlock();
return 0; /* Stick on runq[PriExtra] */
}
DPRINT("%lud edfready %lud[%s] wait release at %lud\n",
now, p->pid, statename[p->state], e->t);
p->state = Waitrelease;
edfunlock();
return -1; /* Make runnable later */
}
DPRINT("%lud edfready %lud %s release now\n", now, p->pid, statename[p->state]);
/* release now */
release(p);
}
edfunlock();
DPRINT("^");
return 1;
}
static void
testenq(Proc *p)
{
Proc *xp, **xpp;
Edf *e;
e = p->edf;
e->testnext = nil;
if (qschedulability == nil) {
qschedulability = p;
return;
}
SET(xp);
for (xpp = &qschedulability; *xpp; xpp = &xp->edf->testnext) {
xp = *xpp;
if (e->testtime - xp->edf->testtime < 0
|| (e->testtime == xp->edf->testtime && e->testtype < xp->edf->testtype)){
e->testnext = xp;
*xpp = p;
return;
}
}
assert(xp->edf->testnext == nil);
xp->edf->testnext = p;
}
static char *
testschedulability(Proc *theproc)
{
Proc *p;
long H, G, Cb, ticks;
int steps, i;
/* initialize */
DPRINT("schedulability test %lud\n", theproc->pid);
qschedulability = nil;
for(i=0; (p = proctab(i)) != nil; i++) {
if(p->state == Dead)
continue;
if((p->edf == nil || (p->edf->flags & Admitted) == 0) && p != theproc)
continue;
p->edf->testtype = Rl;
p->edf->testtime = 0;
DPRINT("\tInit: edfenqueue %lud\n", p->pid);
testenq(p);
}
H=0;
G=0;
for(steps = 0; steps < Maxsteps; steps++){
p = qschedulability;
qschedulability = p->edf->testnext;
ticks = p->edf->testtime;
switch (p->edf->testtype){
case Dl:
H += p->edf->C;
Cb = 0;
DPRINT("\tStep %3d, Ticks %lud, pid %lud, deadline, H += %lud → %lud, Cb = %lud\n",
steps, ticks, p->pid, p->edf->C, H, Cb);
if (H+Cb>ticks){
DPRINT("not schedulable\n");
return "not schedulable";
}
p->edf->testtime += p->edf->T - p->edf->D;
p->edf->testtype = Rl;
testenq(p);
break;
case Rl:
DPRINT("\tStep %3d, Ticks %lud, pid %lud, release, G %lud, C%lud\n",
steps, ticks, p->pid, p->edf->C, G);
if(ticks && G <= ticks){
DPRINT("schedulable\n");
return nil;
}
G += p->edf->C;
p->edf->testtime += p->edf->D;
p->edf->testtype = Dl;
testenq(p);
break;
default:
assert(0);
}
}
DPRINT("probably not schedulable\n");
return "probably not schedulable";
}