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Implement support for cpusets in the 4BSD scheduler.

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- When a cpuset is applied to a thread, walk the cpuset to see if it is a
  "full" cpuset (includes all available CPUs).  If not, set a new
  TDS_AFFINITY flag to indicate that this thread can't run on all CPUs.
  When inheriting a cpuset from another thread during thread creation, the
  new thread also inherits this flag.  It is in a new ts_flags field in
  td_sched rather than using one of the TDF_SCHEDx flags because fork()
  clears td_flags after invoking sched_fork().
- When placing a thread on a runqueue via sched_add(), if the thread is not
  pinned or bound but has the TDS_AFFINITY flag set, then invoke a new
  routine (sched_pickcpu()) to pick a CPU for the thread to run on next.
  sched_pickcpu() walks the cpuset and picks the CPU with the shortest
  per-CPU runqueue length.  Note that the reason for the TDS_AFFINITY flag
  is to avoid having to walk the cpuset and examine runq lengths in the
  common case.
- To avoid walking the per-CPU runqueues in sched_pickcpu(), add an array
  of counters to hold the length of the per-CPU runqueues and update them
  when adding and removing threads to per-CPU runqueues.

MFC after:	2 weeks
This commit is contained in:
John Baldwin 2008-07-28 17:25:24 +00:00
parent eb43240464
commit f200843b72
1 changed files with 116 additions and 0 deletions
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116
sys/kern/sched_4bsd.c
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@ -91,6 +91,7 @@ struct td_sched {
fixpt_t ts_pctcpu; /* (j) %cpu during p_swtime. */
int ts_cpticks; /* (j) Ticks of cpu time. */
int ts_slptime; /* (j) Seconds !RUNNING. */
int ts_flags;
struct runq *ts_runq; /* runq the thread is currently on */
};
@ -98,9 +99,15 @@ struct td_sched {
#define TDF_DIDRUN TDF_SCHED0 /* thread actually ran. */
#define TDF_BOUND TDF_SCHED1 /* Bound to one CPU. */
/* flags kept in ts_flags */
#define TSF_AFFINITY 0x0001 /* Has a non-"full" CPU set. */
#define SKE_RUNQ_PCPU(ts) \
((ts)->ts_runq != 0 && (ts)->ts_runq != &runq)
#define THREAD_CAN_SCHED(td, cpu) \
CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask)
static struct td_sched td_sched0;
struct mtx sched_lock;
@ -118,6 +125,7 @@ static void updatepri(struct thread *td);
static void resetpriority(struct thread *td);
static void resetpriority_thread(struct thread *td);
#ifdef SMP
static int sched_pickcpu(struct thread *td);
static int forward_wakeup(int cpunum);
static void kick_other_cpu(int pri, int cpuid);
#endif
@ -141,6 +149,7 @@ static struct runq runq;
* Per-CPU run queues
*/
static struct runq runq_pcpu[MAXCPU];
long runq_length[MAXCPU];
#endif
static void
@ -733,6 +742,7 @@ sched_fork_thread(struct thread *td, struct thread *childtd)
childtd->td_cpuset = cpuset_ref(td->td_cpuset);
ts = childtd->td_sched;
bzero(ts, sizeof(*ts));
ts->ts_flags |= (td->td_sched->ts_flags & TSF_AFFINITY);
}
void
@ -1149,6 +1159,32 @@ kick_other_cpu(int pri, int cpuid)
}
#endif /* SMP */
#ifdef SMP
static int
sched_pickcpu(struct thread *td)
{
int best, cpu;
mtx_assert(&sched_lock, MA_OWNED);
best = NOCPU;
for (cpu = 0; cpu <= mp_maxid; cpu++) {
if (CPU_ABSENT(cpu))
continue;
if (!THREAD_CAN_SCHED(td, cpu))
continue;
if (best == NOCPU)
best = cpu;
else if (runq_length[cpu] < runq_length[best])
best = cpu;
}
KASSERT(best != NOCPU, ("no valid CPUs"));
return (best);
}
#endif
void
sched_add(struct thread *td, int flags)
#ifdef SMP
@ -1196,6 +1232,14 @@ sched_add(struct thread *td, int flags)
CTR3(KTR_RUNQ,
"sched_add: Put td_sched:%p(td:%p) on cpu%d runq", ts, td,
cpu);
} else if (ts->ts_flags & TSF_AFFINITY) {
/* Find a valid CPU for our cpuset */
cpu = sched_pickcpu(td);
ts->ts_runq = &runq_pcpu[cpu];
single_cpu = 1;
CTR3(KTR_RUNQ,
"sched_add: Put td_sched:%p(td:%p) on cpu%d runq", ts, td,
cpu);
} else {
CTR2(KTR_RUNQ,
"sched_add: adding td_sched:%p (td:%p) to gbl runq", ts,
@ -1227,10 +1271,13 @@ sched_add(struct thread *td, int flags)
if ((td->td_proc->p_flag & P_NOLOAD) == 0)
sched_load_add();
runq_add(ts->ts_runq, td, flags);
if (cpu != NOCPU)
runq_length[cpu]++;
}
#else /* SMP */
{
struct td_sched *ts;
ts = td->td_sched;
THREAD_LOCK_ASSERT(td, MA_OWNED);
KASSERT((td->td_inhibitors == 0),
@ -1292,6 +1339,10 @@ sched_rem(struct thread *td)
if ((td->td_proc->p_flag & P_NOLOAD) == 0)
sched_load_rem();
#ifdef SMP
if (ts->ts_runq != &runq)
runq_length[ts->ts_runq - runq_pcpu]--;
#endif
runq_remove(ts->ts_runq, td);
TD_SET_CAN_RUN(td);
}
@ -1331,6 +1382,10 @@ sched_choose(void)
#endif
if (td) {
#ifdef SMP
if (td == tdcpu)
runq_length[PCPU_GET(cpuid)]--;
#endif
runq_remove(rq, td);
td->td_flags |= TDF_DIDRUN;
@ -1515,4 +1570,65 @@ sched_fork_exit(struct thread *td)
void
sched_affinity(struct thread *td)
{
#ifdef SMP
struct td_sched *ts;
int cpu;
THREAD_LOCK_ASSERT(td, MA_OWNED);
/*
* Set the TSF_AFFINITY flag if there is at least one CPU this
* thread can't run on.
*/
ts = td->td_sched;
ts->ts_flags &= ~TSF_AFFINITY;
for (cpu = 0; cpu <= mp_maxid; cpu++) {
if (CPU_ABSENT(cpu))
continue;
if (!THREAD_CAN_SCHED(td, cpu)) {
ts->ts_flags |= TSF_AFFINITY;
break;
}
}
/*
* If this thread can run on all CPUs, nothing else to do.
*/
if (!(ts->ts_flags & TSF_AFFINITY))
return;
/* Pinned threads and bound threads should be left alone. */
if (td->td_pinned != 0 || td->td_flags & TDF_BOUND)
return;
switch (td->td_state) {
case TDS_RUNQ:
/*
* If we are on a per-CPU runqueue that is in the set,
* then nothing needs to be done.
*/
if (ts->ts_runq != &runq &&
THREAD_CAN_SCHED(td, ts->ts_runq - runq_pcpu))
return;
/* Put this thread on a valid per-CPU runqueue. */
sched_rem(td);
sched_add(td, SRQ_BORING);
break;
case TDS_RUNNING:
/*
* See if our current CPU is in the set. If not, force a
* context switch.
*/
if (THREAD_CAN_SCHED(td, td->td_oncpu))
return;
td->td_flags |= TDF_NEEDRESCHED;
if (td != curthread)
ipi_selected(1 << cpu, IPI_AST);
break;
default:
break;
}
#endif
}