- Add in support for KSEs with 0 slice values on the run queue. If we try
to select a KSE with a slice of 0 we will update its slice and insert it onto the next queue. - Pass the KSE instead of the ksegrp into sched_slice(). This more accurately reflects the behavior of the code. Slices are granted to kses. - Add a function kseq_nice_min() which finds the smallest nice value assigned to the kseg of any KSE on the queue. - Rewrite the logic in sched_slice(). Add a large comment describing the new slice selection scheme. To summarize, slices are assigned based on the nice value. Priorities are still calculated based on the nice and interactivity of a process. Slice sizes of 0 may be granted for KSEs whos nice is 20 or futher away from the lowest nice on the run queue. Other nice values are scaled across the range [min, min+20]. This fixes ULEs bad behavior with positively niced processes.
This commit is contained in:
Jeff Roberson
parent
26f52e2f8b
commit
245f3abfd5
@ -33,6 +33,7 @@
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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/resource.h>
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#include <sys/sched.h>
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#include <sys/smp.h>
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#include <sys/sx.h>
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@ -123,7 +124,8 @@ struct td_sched *thread0_sched = &td_sched;
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* running vs the total number of ticks.
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*/
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#define SCHED_PRI_RANGE (PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE + 1)
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#define SCHED_PRI_NRESV 40
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#define SCHED_PRI_NRESV PRIO_TOTAL
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#define SCHED_PRI_NHALF (PRIO_TOTAL >> 2)
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#define SCHED_PRI_BASE ((SCHED_PRI_NRESV / 2) + PRI_MIN_TIMESHARE)
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#define SCHED_DYN_RANGE (SCHED_PRI_RANGE - SCHED_PRI_NRESV)
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#define SCHED_DYN_HALF (SCHED_DYN_RANGE / 2)
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@ -153,25 +155,15 @@ struct td_sched *thread0_sched = &td_sched;
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* SLICE_MIN: Minimum time slice granted, in units of ticks.
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* SLICE_MAX: Maximum time slice granted.
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* SLICE_RANGE: Range of available time slices scaled by hz.
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* SLICE_SCALE: The number slices granted per unit of pri or slp.
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* PRI_TOSLICE: Compute a slice size that is proportional to the priority.
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* INTERACT_TOSLICE: Compute a slice size that is inversely proportional to
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* the amount of time slept. (smaller slices for interactive ksegs)
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* PRI_COMP: This determines what fraction of the actual slice comes from
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* the slice size computed from the priority.
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* INTERACT_COMP:This determines what component of the actual slice comes from
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* the slize size computed from the interactivity score.
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* SLICE_SCALE: The number slices granted per val in the range of [0, max].
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* SLICE_NICE: Determine the amount of slice granted to a scaled nice.
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*/
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#define SCHED_SLICE_MIN (hz / 100)
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#define SCHED_SLICE_MAX (hz / 10)
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#define SCHED_SLICE_RANGE (SCHED_SLICE_MAX - SCHED_SLICE_MIN + 1)
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#define SCHED_SLICE_SCALE(val, max) (((val) * SCHED_SLICE_RANGE) / (max))
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#define SCHED_INTERACT_COMP(slice) ((slice) / 2) /* 50% */
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#define SCHED_PRI_COMP(slice) ((slice) / 2) /* 50% */
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#define SCHED_PRI_TOSLICE(pri) \
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(SCHED_SLICE_MAX - SCHED_SLICE_SCALE((pri), SCHED_PRI_RANGE))
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#define SCHED_INTERACT_TOSLICE(score) \
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(SCHED_SLICE_SCALE((score), SCHED_INTERACT_RANGE))
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#define SCHED_SLICE_NICE(nice) \
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(SCHED_SLICE_MAX - SCHED_SLICE_SCALE((nice), SCHED_PRI_NHALF))
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/*
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* This macro determines whether or not the kse belongs on the current or
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@ -219,7 +211,7 @@ struct kseq kseq_cpu;
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#define KSEQ_CPU(x) (&kseq_cpu)
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#endif
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static int sched_slice(struct ksegrp *kg);
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static void sched_slice(struct kse *ke);
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static int sched_priority(struct ksegrp *kg);
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static int sched_interact_score(struct ksegrp *kg);
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void sched_pctcpu_update(struct kse *ke);
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@ -227,6 +219,7 @@ int sched_pickcpu(void);
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/* Operations on per processor queues */
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static struct kse * kseq_choose(struct kseq *kseq);
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static int kseq_nice_min(struct kseq *kseq);
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static void kseq_setup(struct kseq *kseq);
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static __inline void kseq_add(struct kseq *kseq, struct kse *ke);
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static __inline void kseq_rem(struct kseq *kseq, struct kse *ke);
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@ -311,6 +304,26 @@ kseq_choose(struct kseq *kseq)
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return (ke);
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}
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static int
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kseq_nice_min(struct kseq *kseq)
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{
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struct kse *ke0;
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struct kse *ke1;
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if (kseq->ksq_load == 0)
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return (0);
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ke0 = runq_choose(kseq->ksq_curr);
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ke1 = runq_choose(kseq->ksq_next);
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if (ke0 == NULL)
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return (ke1->ke_ksegrp->kg_nice);
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if (ke1 == NULL)
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return (ke0->ke_ksegrp->kg_nice);
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return (min(ke0->ke_ksegrp->kg_nice, ke1->ke_ksegrp->kg_nice));
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}
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static void
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kseq_setup(struct kseq *kseq)
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@ -367,26 +380,56 @@ sched_priority(struct ksegrp *kg)
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}
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/*
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* Calculate a time slice based on the process priority.
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* Calculate a time slice based on the properties of the kseg and the runq
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* that we're on.
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*/
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static int
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sched_slice(struct ksegrp *kg)
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static void
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sched_slice(struct kse *ke)
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{
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int pslice;
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int islice;
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int slice;
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int pri;
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struct ksegrp *kg;
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pri = kg->kg_user_pri;
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pri -= PRI_MIN_TIMESHARE;
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pslice = SCHED_PRI_TOSLICE(pri);
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islice = SCHED_INTERACT_TOSLICE(sched_interact_score(kg));
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slice = SCHED_INTERACT_COMP(islice) + SCHED_PRI_COMP(pslice);
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kg = ke->ke_ksegrp;
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if (slice < SCHED_SLICE_MIN)
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slice = SCHED_SLICE_MIN;
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else if (slice > SCHED_SLICE_MAX)
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slice = SCHED_SLICE_MAX;
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/*
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* Rationale:
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* KSEs in interactive ksegs get the minimum slice so that we
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* quickly notice if it abuses its advantage.
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*
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* KSEs in non-interactive ksegs are assigned a slice that is
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* based on the ksegs nice value relative to the least nice kseg
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* on the run queue for this cpu.
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*
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* If the KSE is less nice than all others it gets the maximum
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* slice and other KSEs will adjust their slice relative to
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* this when they first expire.
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*
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* There is 20 point window that starts relative to the least
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* nice kse on the run queue. Slice size is determined by
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* the kse distance from the last nice ksegrp.
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*
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* If you are outside of the window you will get no slice and
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* you will be reevaluated each time you are selected on the
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* run queue.
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*
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*/
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if (!SCHED_CURR(kg)) {
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struct kseq *kseq;
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int nice_base;
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int nice;
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kseq = KSEQ_CPU(ke->ke_cpu);
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nice_base = kseq_nice_min(kseq);
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nice = kg->kg_nice + (0 - nice_base);
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if (kseq->ksq_load == 0 || kg->kg_nice < nice_base)
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ke->ke_slice = SCHED_SLICE_MAX;
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else if (nice <= SCHED_PRI_NHALF)
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ke->ke_slice = SCHED_SLICE_NICE(nice);
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else
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ke->ke_slice = 0;
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} else
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ke->ke_slice = SCHED_SLICE_MIN;
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/*
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* Every time we grant a new slice check to see if we need to scale
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@ -398,7 +441,7 @@ sched_slice(struct ksegrp *kg)
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kg->kg_slptime /= SCHED_SLP_RUN_THROTTLE;
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}
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return (slice);
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return;
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}
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static int
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@ -723,7 +766,7 @@ sched_clock(struct thread *td)
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*/
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if (ke->ke_slice <= 0) {
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sched_priority(kg);
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ke->ke_slice = sched_slice(kg);
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sched_slice(ke);
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td->td_flags |= TDF_NEEDRESCHED;
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ke->ke_runq = NULL;
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}
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@ -784,11 +827,24 @@ sched_choose(void)
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struct kse *ke;
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kseq = KSEQ_SELF();
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retry:
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ke = kseq_choose(kseq);
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if (ke) {
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ke->ke_state = KES_THREAD;
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kseq_rem(kseq, ke);
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/*
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* If we dequeue a kse with a slice of zero it was below the
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* nice threshold to acquire a slice. Recalculate the slice
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* to see if the situation has changed and then requeue.
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*/
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if (ke->ke_slice == 0) {
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sched_slice(ke);
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ke->ke_runq = kseq->ksq_next;
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kseq_add(kseq, ke);
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goto retry;
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}
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}
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#ifdef SMP
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