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sysfs,cpuallocator: add support for hybrid core discovery, preferred allocation. #295

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merged 6 commits into from
Mar 27, 2024
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sysfs,cpuallocator: add support for hybrid core discovery, preferred allocation. #295

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a09ad34
sysfs: add support for hybrid core architectures.
klihub Mar 12, 2024
f30f335
sysfs: allow overriding core type detection.
klihub Mar 18, 2024
7cdc6cc
cpuallocator: update test data.
klihub Mar 18, 2024
fe9be5a
cpuallocator: prefer E-cores for low-prio allocation.
klihub Mar 18, 2024
dbf3a3a
cpuallocator: prefer P-cores for high-prio allocation.
klihub Mar 23, 2024
fef72fc
cpuallocator: make idle package allocation core type aware.
klihub Mar 18, 2024
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99 changes: 86 additions & 13 deletions pkg/cpuallocator/allocator.go
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Original file line number Diff line number Diff line change
Expand Up @@ -88,10 +88,10 @@ type topologyCache struct {
pkg map[idset.ID]cpuset.CPUSet
node map[idset.ID]cpuset.CPUSet
core map[idset.ID]cpuset.CPUSet
kind map[sysfs.CoreKind]cpuset.CPUSet

cpuPriorities cpuPriorities // CPU priority mapping
clusters []*cpuCluster // CPU clusters

}

type cpuPriorities [NumCPUPriorities]cpuset.CPUSet
Expand All @@ -101,6 +101,7 @@ type cpuCluster struct {
die idset.ID
cluster idset.ID
cpus cpuset.CPUSet
kind sysfs.CoreKind
}

// IDFilter helps filtering Ids.
Expand Down Expand Up @@ -159,7 +160,14 @@ func (a *allocatorHelper) takeIdlePackages() {
// pick idle packages
pkgs := pickIds(a.sys.PackageIDs(),
func(id idset.ID) bool {
// Consider a package idle if all online preferred CPUs are idle.
// In particular, on hybrid core architectures exclude
// - exclude E-cores from allocations with <= PriorityNormal preference
// - exclude P-cores from allocations with > PriorityLow preferences
cset := a.topology.pkg[id].Difference(offline)
if a.prefer < NumCPUPriorities {
cset = cset.Intersection(a.topology.cpuPriorities[a.prefer])
}
return cset.Intersection(a.from).Equals(cset)
})

Expand All @@ -177,6 +185,9 @@ func (a *allocatorHelper) takeIdlePackages() {
// take as many idle packages as we need/can
for _, id := range pkgs {
cset := a.topology.pkg[id].Difference(offline)
if a.prefer < NumCPUPriorities {
cset = cset.Intersection(a.topology.cpuPriorities[a.prefer])
}
a.Debug(" => considering package %v (#%s)...", id, cset)
if a.cnt >= cset.Size() {
a.Debug(" => taking package %v...", id)
Expand All @@ -200,6 +211,17 @@ func (a *allocatorHelper) takeIdleClusters() {
var (
offline = a.sys.OfflineCPUs()
pickIdle = func(c *cpuCluster) (bool, cpuset.CPUSet) {
// we only take E-clusters for low-prio requests
if a.prefer != PriorityLow && c.kind == sysfs.EfficientCore {
a.Debug(" - omit %s, CPU preference is %s", c, a.prefer)
return false, emptyCPUSet
}
// we only take P-clusters for other than low-prio requests
if a.prefer == PriorityLow && c.kind == sysfs.PerformanceCore {
a.Debug(" - omit %s, CPU preference is %s", c, a.prefer)
return false, emptyCPUSet
}

// we only take fully idle clusters
cset := c.cpus.Difference(offline)
free := cset.Intersection(a.from)
Expand Down Expand Up @@ -692,9 +714,17 @@ func (c *topologyCache) discoverCPUPriorities(sys sysfs.System) {
cpuPriorities = c.discoverCpufreqPriority(sys, id)
}

ecores := c.kind[sysfs.EfficientCore]
ocores := sys.OnlineCPUs().Difference(ecores)

for p, cpus := range cpuPriorities {
source := map[bool]string{true: "sst", false: "cpufreq"}[sstActive]
cset := sysfs.CPUSetFromIDSet(idset.NewIDSet(cpus...))

if p != int(PriorityLow) && ocores.Size() > 0 {
cset = cset.Difference(ecores)
}

log.Debug("package #%d (%s): %d %s priority cpus (%v)", id, source, len(cpus), CPUPriority(p), cset)
prio[p] = prio[p].Union(cset)
}
Expand Down Expand Up @@ -826,7 +856,7 @@ func (c *topologyCache) sstClosPriority(sys sysfs.System, pkgID idset.ID) map[in
func (c *topologyCache) discoverCpufreqPriority(sys sysfs.System, pkgID idset.ID) [NumCPUPriorities][]idset.ID {
var prios [NumCPUPriorities][]idset.ID

// Group cpus by base frequency and energy performance profile
// Group cpus by base frequency, core kind and energy performance profile
freqs := map[uint64][]idset.ID{}
epps := map[sysfs.EPP][]idset.ID{}
cpuIDs := c.pkg[pkgID].List()
Expand Down Expand Up @@ -874,14 +904,19 @@ func (c *topologyCache) discoverCpufreqPriority(sys sysfs.System, pkgID idset.ID
}
}

// All cpus NOT in the lowest performance epp are considered high prio
// All E-cores are unconditionally considered low prio.
// All cpus NOT in the lowest performance epp are considered high prio.
// NOTE: higher EPP value denotes lower performance preference
if len(eppList) > 1 {
epp := cpu.EPP()
if int(epp) < eppList[len(eppList)-1] {
p = PriorityHigh
} else {
p = PriorityLow
if cpu.CoreKind() == sysfs.EfficientCore {
p = PriorityLow
} else {
if len(eppList) > 1 {
epp := cpu.EPP()
if int(epp) < eppList[len(eppList)-1] {
p = PriorityHigh
} else {
p = PriorityLow
}
}
}

Expand All @@ -907,18 +942,24 @@ func (c *topologyCache) discoverCPUClusters(sys sysfs.System) {
die: die,
cluster: cl,
cpus: cpus,
kind: sys.CPU(cpus.List()[0]).CoreKind(),
})
}
}
if len(clusters) > 1 {
log.Debug("package #%d has %d clusters:", id, len(clusters))
for _, cl := range clusters {
log.Debug(" die #%d, cluster #%d: cpus %s",
cl.die, cl.cluster, cl.cpus)
log.Debug(" die #%d, cluster #%d: %s cpus %s",
cl.die, cl.cluster, cl.kind, cl.cpus)
}
c.clusters = append(c.clusters, clusters...)
}
}

c.kind = map[sysfs.CoreKind]cpuset.CPUSet{}
for _, kind := range sys.CoreKinds() {
c.kind[kind] = sys.CoreKindCPUs(kind)
}
}

func (p CPUPriority) String() string {
Expand All @@ -943,6 +984,38 @@ func (c *cpuPriorities) cmpCPUSet(csetA, csetB cpuset.CPUSet, prefer CPUPriority
return 0
}

// For low prio request, favor cpuset with the tightest fit.
if cpuCnt > 0 && prefer == PriorityLow {
prefA := csetA.Intersection(c[prefer]).Size()
prefB := csetB.Intersection(c[prefer]).Size()
// both sets have enough preferred CPUs, return the smaller one (tighter fit)
if prefA >= cpuCnt && prefB >= cpuCnt {
return prefB - prefA
}
// only one set has enough preferred CPUs, return the bigger/only one
if prefA >= cpuCnt || prefB >= cpuCnt {
return prefA - prefB
}
}

// For high prio request, favor the tightest fit falling back to normal prio
if cpuCnt > 0 && prefer == PriorityHigh {
prefA := csetA.Intersection(c[prefer]).Size()
prefB := csetB.Intersection(c[prefer]).Size()
if prefA == 0 && prefB == 0 {
prefA = csetA.Intersection(c[PriorityNormal]).Size()
prefB = csetB.Intersection(c[PriorityNormal]).Size()
}
// both sets have enough preferred CPUs, return the smaller one (tighter fit)
if prefA >= cpuCnt && prefB >= cpuCnt {
return prefB - prefA
}
// only one set has enough preferred CPUs, return the bigger/only one
if prefA >= cpuCnt || prefB >= cpuCnt {
return prefA - prefB
}
}

// Favor cpuset having CPUs with priorities equal to or lower than what was requested
for prio := prefer; prio < NumCPUPriorities; prio++ {
prefA := csetA.Intersection(c[prio]).Size()
Expand Down Expand Up @@ -984,6 +1057,6 @@ func (c *cpuCluster) HasSmallerIDsThan(o *cpuCluster) bool {
}

func (c *cpuCluster) String() string {
return fmt.Sprintf("cluster #%d/%d/%d, %d CPUs (%s)", c.pkg, c.die, c.cluster,
c.cpus.Size(), c.cpus)
return fmt.Sprintf("cluster #%d/%d/%d, %d %s CPUs (%s)", c.pkg, c.die, c.cluster,
c.cpus.Size(), c.kind, c.cpus)
}
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