Add takeByTopologyUnCoreCachePacked if policy option align-cpus-by-uncorecache is enabled.

 Adding new function to evaluate uncore cache id. Reverse allocation logic.
 Implement preferAlignByUncorecache within TakeByTopologyNUMAPacked, along with new test cases.

Author: sphrasavath

pkg/kubelet/cm/cpumanager/cpu_assignment.go

@@ -118,6 +118,17 @@ func (n *numaFirst) takeFullSecondLevel() {
 	n.acc.takeFullSockets()
 }
 
+// Sort the UncoreCaches within the NUMA nodes.
+func (a *cpuAccumulator) sortAvailableUncoreCaches() []int {
+	var result []int
+	for _, numa := range a.sortAvailableNUMANodes() {
+		uncore := a.details.UncoreInNUMANodes(numa).UnsortedList()
+		a.sort(uncore, a.details.CPUsInUncoreCaches)
+		result = append(result, uncore...)
+	}
+	return result
+}
+
 // If NUMA nodes are higher in the memory hierarchy than sockets, then just
 // sort the NUMA nodes directly, and return them.
 func (n *numaFirst) sortAvailableNUMANodes() []int {
@@ -318,6 +329,12 @@ func (a *cpuAccumulator) isSocketFree(socketID int) bool {
 	return a.details.CPUsInSockets(socketID).Size() == a.topo.CPUsPerSocket()
 }
 
+// Returns true if the supplied UnCoreCache is fully available,
+// "fully available" means that all the CPUs in it are free.
+func (a *cpuAccumulator) isUncoreCacheFree(uncoreID int) bool {
+	return a.details.CPUsInUncoreCaches(uncoreID).Size() == a.topo.CPUDetails.CPUsInUncoreCaches(uncoreID).Size()
+}
+
 // Returns true if the supplied core is fully available in `a.details`.
 // "fully available" means that all the CPUs in it are free.
 func (a *cpuAccumulator) isCoreFree(coreID int) bool {
@@ -346,6 +363,17 @@ func (a *cpuAccumulator) freeSockets() []int {
 	return free
 }
 
+// Returns free UncoreCache IDs as a slice sorted by sortAvailableUnCoreCache().
+func (a *cpuAccumulator) freeUncoreCache() []int {
+	free := []int{}
+	for _, uncore := range a.sortAvailableUncoreCaches() {
+		if a.isUncoreCacheFree(uncore) {
+			free = append(free, uncore)
+		}
+	}
+	return free
+}
+
 // Returns free core IDs as a slice sorted by sortAvailableCores().
 func (a *cpuAccumulator) freeCores() []int {
 	free := []int{}
@@ -519,6 +547,60 @@ func (a *cpuAccumulator) takeFullSockets() {
 	}
 }
 
+func (a *cpuAccumulator) takeFullUncore() {
+	for _, uncore := range a.freeUncoreCache() {
+		cpusInUncore := a.topo.CPUDetails.CPUsInUncoreCaches(uncore)
+		if !a.needsAtLeast(cpusInUncore.Size()) {
+			continue
+		}
+		klog.V(4).InfoS("takeFullUncore: claiming uncore", "uncore", uncore)
+		a.take(cpusInUncore)
+	}
+}
+
+func (a *cpuAccumulator) takePartialUncore(uncoreID int) {
+	numCoresNeeded := a.numCPUsNeeded / a.topo.CPUsPerCore()
+
+	// note: we need to keep the first N free cores (physical cpus) and only we we got these expand to their
+	// cpus (virtual cpus). Taking directly the first M cpus (virtual cpus) leads to suboptimal allocation
+	freeCores := a.details.CoresNeededInUncoreCache(numCoresNeeded, uncoreID)
+	freeCPUs := a.details.CPUsInCores(freeCores.UnsortedList()...)
+
+	claimed := (a.numCPUsNeeded == freeCPUs.Size())
+	klog.V(4).InfoS("takePartialUncore: trying to claim partial uncore",
+		"uncore", uncoreID,
+		"claimed", claimed,
+		"needed", a.numCPUsNeeded,
+		"cores", freeCores.String(),
+		"cpus", freeCPUs.String())
+	if !claimed {
+		return
+
+	}
+	a.take(freeCPUs)
+}
+
+// First try to take full UncoreCache, if available and need is at least the size of the UncoreCache group.
+// Second try to take the partial UncoreCache if available and the request size can fit w/in the UncoreCache.
+func (a *cpuAccumulator) takeUncoreCache() {
+	numCPUsInUncore := a.topo.CPUsPerUncore()
+	for _, uncore := range a.sortAvailableUncoreCaches() {
+		// take full UncoreCache if the CPUs needed is greater than free UncoreCache size
+		if a.needsAtLeast(numCPUsInUncore) {
+			a.takeFullUncore()
+		}
+
+		if a.isSatisfied() {
+			return
+		}
+
+		a.takePartialUncore(uncore)
+		if a.isSatisfied() {
+			return
+		}
+	}
+}
+
 func (a *cpuAccumulator) takeFullCores() {
 	for _, core := range a.freeCores() {
 		cpusInCore := a.topo.CPUDetails.CPUsInCores(core)
@@ -637,6 +719,14 @@ func (a *cpuAccumulator) iterateCombinations(n []int, k int, f func([]int) LoopC
 // or the remaining number of CPUs to take after having taken full sockets and NUMA nodes is less
 // than a whole NUMA node, the function tries to take whole physical cores (cores).
 //
+// If `PreferAlignByUncoreCache` is enabled, the function will try to optimally assign Uncorecaches.
+// If `numCPUs` is larger than or equal to the total number of CPUs in a Uncorecache, and there are
+// free (i.e. all CPUs within the Uncorecache are free) Uncorecaches, the function takes as many entire
+// cores from free Uncorecaches as possible. If/Once `numCPUs` is smaller than the total number of
+// CPUs in a free Uncorecache, the function scans each Uncorecache index in numerical order to assign
+// cores that will fit within the Uncorecache. If `numCPUs` cannot fit within any Uncorecache, the
+// function tries to take whole physical cores.
+//
 // If `numCPUs` is bigger than the total number of CPUs in a core, and there are
 // free (i.e. all CPUs in them are free) cores, the function takes as many entire free cores as possible.
 // The cores are taken from one socket at a time, and the sockets are considered by
@@ -658,7 +748,7 @@ func (a *cpuAccumulator) iterateCombinations(n []int, k int, f func([]int) LoopC
 // the least amount of free CPUs to the one with the highest amount of free CPUs (i.e. in ascending
 // order of free CPUs). For any NUMA node, the cores are selected from the ones in the socket with
 // the least amount of free CPUs to the one with the highest amount of free CPUs.
-func takeByTopologyNUMAPacked(topo *topology.CPUTopology, availableCPUs cpuset.CPUSet, numCPUs int, cpuSortingStrategy CPUSortingStrategy) (cpuset.CPUSet, error) {
+func takeByTopologyNUMAPacked(topo *topology.CPUTopology, availableCPUs cpuset.CPUSet, numCPUs int, cpuSortingStrategy CPUSortingStrategy, preferAlignByUncoreCache bool) (cpuset.CPUSet, error) {
 	acc := newCPUAccumulator(topo, availableCPUs, numCPUs, cpuSortingStrategy)
 	if acc.isSatisfied() {
 		return acc.result, nil
@@ -681,7 +771,17 @@ func takeByTopologyNUMAPacked(topo *topology.CPUTopology, availableCPUs cpuset.C
 		return acc.result, nil
 	}
 
-	// 2. Acquire whole cores, if available and the container requires at least
+	// 2. If PreferAlignByUncoreCache is enabled, acquire whole UncoreCaches
+	//    if available and the container requires at least a UncoreCache's-worth
+	//    of CPUs. Otherwise, acquire CPUs from the least amount of UncoreCaches.
+	if preferAlignByUncoreCache {
+		acc.takeUncoreCache()
+		if acc.isSatisfied() {
+			return acc.result, nil
+		}
+	}
+
+	// 3. Acquire whole cores, if available and the container requires at least
 	//    a core's-worth of CPUs.
 	//    If `CPUSortingStrategySpread` is specified, skip taking the whole core.
 	if cpuSortingStrategy != CPUSortingStrategySpread {
@@ -691,7 +791,7 @@ func takeByTopologyNUMAPacked(topo *topology.CPUTopology, availableCPUs cpuset.C
 		}
 	}
 
-	// 3. Acquire single threads, preferring to fill partially-allocated cores
+	// 4. Acquire single threads, preferring to fill partially-allocated cores
 	//    on the same sockets as the whole cores we have already taken in this
 	//    allocation.
 	acc.takeRemainingCPUs()
@@ -769,8 +869,10 @@ func takeByTopologyNUMADistributed(topo *topology.CPUTopology, availableCPUs cpu
 	// If the number of CPUs requested cannot be handed out in chunks of
 	// 'cpuGroupSize', then we just call out the packing algorithm since we
 	// can't distribute CPUs in this chunk size.
+	// PreferAlignByUncoreCache feature not implemented here yet and set to false.
+	// Support for PreferAlignByUncoreCache to be done at beta release.
 	if (numCPUs % cpuGroupSize) != 0 {
-		return takeByTopologyNUMAPacked(topo, availableCPUs, numCPUs, cpuSortingStrategy)
+		return takeByTopologyNUMAPacked(topo, availableCPUs, numCPUs, cpuSortingStrategy, false)
 	}
 
 	// Otherwise build an accumulator to start allocating CPUs from.
@@ -953,7 +1055,7 @@ func takeByTopologyNUMADistributed(topo *topology.CPUTopology, availableCPUs cpu
 		// size 'cpuGroupSize' from 'bestCombo'.
 		distribution := (numCPUs / len(bestCombo) / cpuGroupSize) * cpuGroupSize
 		for _, numa := range bestCombo {
-			cpus, _ := takeByTopologyNUMAPacked(acc.topo, acc.details.CPUsInNUMANodes(numa), distribution, cpuSortingStrategy)
+			cpus, _ := takeByTopologyNUMAPacked(acc.topo, acc.details.CPUsInNUMANodes(numa), distribution, cpuSortingStrategy, false)
 			acc.take(cpus)
 		}
 
@@ -968,7 +1070,7 @@ func takeByTopologyNUMADistributed(topo *topology.CPUTopology, availableCPUs cpu
 				if acc.details.CPUsInNUMANodes(numa).Size() < cpuGroupSize {
 					continue
 				}
-				cpus, _ := takeByTopologyNUMAPacked(acc.topo, acc.details.CPUsInNUMANodes(numa), cpuGroupSize, cpuSortingStrategy)
+				cpus, _ := takeByTopologyNUMAPacked(acc.topo, acc.details.CPUsInNUMANodes(numa), cpuGroupSize, cpuSortingStrategy, false)
 				acc.take(cpus)
 				remainder -= cpuGroupSize
 			}
@@ -992,5 +1094,5 @@ func takeByTopologyNUMADistributed(topo *topology.CPUTopology, availableCPUs cpu
 
 	// If we never found a combination of NUMA nodes that we could properly
 	// distribute CPUs across, fall back to the packing algorithm.
-	return takeByTopologyNUMAPacked(topo, availableCPUs, numCPUs, cpuSortingStrategy)
+	return takeByTopologyNUMAPacked(topo, availableCPUs, numCPUs, cpuSortingStrategy, false)
 }

pkg/kubelet/cm/cpumanager/cpu_assignment_test.go

@@ -668,6 +668,79 @@ func TestTakeByTopologyNUMAPacked(t *testing.T) {
 			"",
 			mustParseCPUSet(t, "0-29,40-69,30,31,70,71"),
 		},
+		// Test cases for PreferAlignByUncoreCache
+		{
+			"take cpus from two full UncoreCaches and partial from a single UncoreCache",
+			topoUncoreSingleSocketNoSMT,
+			StaticPolicyOptions{PreferAlignByUncoreCacheOption: true},
+			mustParseCPUSet(t, "1-15"),
+			10,
+			"",
+			cpuset.New(1, 2, 4, 5, 6, 7, 8, 9, 10, 11),
+		},
+		{
+			"take one cpu from dual socket with HT - core from Socket 0",
+			topoDualSocketHT,
+			StaticPolicyOptions{PreferAlignByUncoreCacheOption: true},
+			cpuset.New(1, 2, 3, 4, 5, 7, 8, 9, 10, 11),
+			1,
+			"",
+			cpuset.New(2),
+		},
+		{
+			"take first available UncoreCache from first socket",
+			topoUncoreDualSocketNoSMT,
+			StaticPolicyOptions{PreferAlignByUncoreCacheOption: true},
+			mustParseCPUSet(t, "0-15"),
+			4,
+			"",
+			cpuset.New(0, 1, 2, 3),
+		},
+		{
+			"take all available UncoreCache from first socket",
+			topoUncoreDualSocketNoSMT,
+			StaticPolicyOptions{PreferAlignByUncoreCacheOption: true},
+			mustParseCPUSet(t, "2-15"),
+			6,
+			"",
+			cpuset.New(2, 3, 4, 5, 6, 7),
+		},
+		{
+			"take first available UncoreCache from second socket",
+			topoUncoreDualSocketNoSMT,
+			StaticPolicyOptions{PreferAlignByUncoreCacheOption: true},
+			mustParseCPUSet(t, "8-15"),
+			4,
+			"",
+			cpuset.New(8, 9, 10, 11),
+		},
+		{
+			"take first available UncoreCache from available NUMA",
+			topoUncoreSingleSocketMultiNuma,
+			StaticPolicyOptions{PreferAlignByUncoreCacheOption: true},
+			mustParseCPUSet(t, "3,4-8,12"),
+			2,
+			"",
+			cpuset.New(4, 5),
+		},
+		{
+			"take cpus from best available UncoreCache group of multi uncore cache single socket - SMT enabled",
+			topoUncoreSingleSocketSMT,
+			StaticPolicyOptions{PreferAlignByUncoreCacheOption: true},
+			mustParseCPUSet(t, "2-3,10-11,4-7,12-15"),
+			6,
+			"",
+			cpuset.New(4, 5, 6, 12, 13, 14),
+		},
+		{
+			"take cpus from multiple UncoreCache of single socket - SMT enabled",
+			topoUncoreSingleSocketSMT,
+			StaticPolicyOptions{PreferAlignByUncoreCacheOption: true},
+			mustParseCPUSet(t, "1-7,9-15"),
+			10,
+			"",
+			mustParseCPUSet(t, "4-7,12-15,1,9"),
+		},
 	}...)
 
 	for _, tc := range testCases {
@@ -677,7 +750,7 @@ func TestTakeByTopologyNUMAPacked(t *testing.T) {
 				strategy = CPUSortingStrategySpread
 			}
 
-			result, err := takeByTopologyNUMAPacked(tc.topo, tc.availableCPUs, tc.numCPUs, strategy)
+			result, err := takeByTopologyNUMAPacked(tc.topo, tc.availableCPUs, tc.numCPUs, strategy, tc.opts.PreferAlignByUncoreCacheOption)
 			if tc.expErr != "" && err != nil && err.Error() != tc.expErr {
 				t.Errorf("expected error to be [%v] but it was [%v]", tc.expErr, err)
 			}
@@ -778,7 +851,7 @@ func TestTakeByTopologyWithSpreadPhysicalCPUsPreferredOption(t *testing.T) {
 		if tc.opts.DistributeCPUsAcrossCores {
 			strategy = CPUSortingStrategySpread
 		}
-		result, err := takeByTopologyNUMAPacked(tc.topo, tc.availableCPUs, tc.numCPUs, strategy)
+		result, err := takeByTopologyNUMAPacked(tc.topo, tc.availableCPUs, tc.numCPUs, strategy, tc.opts.PreferAlignByUncoreCacheOption)
 		if tc.expErr != "" && err.Error() != tc.expErr {
 			t.Errorf("testCase %q failed, expected error to be [%v] but it was [%v]", tc.description, tc.expErr, err)
 		}

pkg/kubelet/cm/cpumanager/cpu_manager_test.go

@@ -668,20 +668,24 @@ func TestCPUManagerGenerate(t *testing.T) {
 			{
 				Cores: []cadvisorapi.Core{
 					{
-						Id:      0,
-						Threads: []int{0},
+						Id:           0,
+						Threads:      []int{0},
+						UncoreCaches: []cadvisorapi.Cache{{Id: 1}},
 					},
 					{
-						Id:      1,
-						Threads: []int{1},
+						Id:           1,
+						Threads:      []int{1},
+						UncoreCaches: []cadvisorapi.Cache{{Id: 1}},
 					},
 					{
-						Id:      2,
-						Threads: []int{2},
+						Id:           2,
+						Threads:      []int{2},
+						UncoreCaches: []cadvisorapi.Cache{{Id: 1}},
 					},
 					{
-						Id:      3,
-						Threads: []int{3},
+						Id:           3,
+						Threads:      []int{3},
+						UncoreCaches: []cadvisorapi.Cache{{Id: 1}},
 					},
 				},
 			},

pkg/kubelet/cm/cpumanager/policy_options.go

@@ -34,6 +34,7 @@ const (
 	AlignBySocketOption             string = "align-by-socket"
 	DistributeCPUsAcrossCoresOption string = "distribute-cpus-across-cores"
 	StrictCPUReservationOption      string = "strict-cpu-reservation"
+	PreferAlignByUnCoreCacheOption  string = "prefer-align-cpus-by-uncorecache"
 )
 
 var (
@@ -42,6 +43,7 @@ var (
 		AlignBySocketOption,
 		DistributeCPUsAcrossCoresOption,
 		StrictCPUReservationOption,
+		PreferAlignByUnCoreCacheOption,
 	)
 	betaOptions = sets.New[string](
 		FullPCPUsOnlyOption,
@@ -90,6 +92,9 @@ type StaticPolicyOptions struct {
 	DistributeCPUsAcrossCores bool
 	// Flag to remove reserved cores from the list of available cores
 	StrictCPUReservation bool
+	// Flag that makes best-effort to align CPUs to a uncorecache boundary
+	// As long as there are CPUs available, pods will be admitted if the condition is not met.
+	PreferAlignByUncoreCacheOption bool
 }
 
 // NewStaticPolicyOptions creates a StaticPolicyOptions struct from the user configuration.
@@ -131,6 +136,12 @@ func NewStaticPolicyOptions(policyOptions map[string]string) (StaticPolicyOption
 				return opts, fmt.Errorf("bad value for option %q: %w", name, err)
 			}
 			opts.StrictCPUReservation = optValue
+		case PreferAlignByUnCoreCacheOption:
+			optValue, err := strconv.ParseBool(value)
+			if err != nil {
+				return opts, fmt.Errorf("bad value for option %q: %w", name, err)
+			}
+			opts.PreferAlignByUncoreCacheOption = optValue
 		default:
 			// this should never be reached, we already detect unknown options,
 			// but we keep it as further safety.
@@ -147,6 +158,14 @@ func NewStaticPolicyOptions(policyOptions map[string]string) (StaticPolicyOption
 		return opts, fmt.Errorf("static policy options %s and %s can not be used at the same time", DistributeCPUsAcrossNUMAOption, DistributeCPUsAcrossCoresOption)
 	}
 
+	if opts.PreferAlignByUncoreCacheOption && opts.DistributeCPUsAcrossCores {
+		return opts, fmt.Errorf("static policy options %s and %s can not be used at the same time", PreferAlignByUnCoreCacheOption, DistributeCPUsAcrossCoresOption)
+	}
+
+	if opts.PreferAlignByUncoreCacheOption && opts.DistributeCPUsAcrossNUMA {
+		return opts, fmt.Errorf("static policy options %s and %s can not be used at the same time", PreferAlignByUnCoreCacheOption, DistributeCPUsAcrossNUMAOption)
+	}
+
 	return opts, nil
 }
 

pkg/kubelet/cm/cpumanager/policy_static.go

@@ -525,7 +525,8 @@ func (p *staticPolicy) takeByTopology(availableCPUs cpuset.CPUSet, numCPUs int)
 		}
 		return takeByTopologyNUMADistributed(p.topology, availableCPUs, numCPUs, cpuGroupSize, cpuSortingStrategy)
 	}
-	return takeByTopologyNUMAPacked(p.topology, availableCPUs, numCPUs, cpuSortingStrategy)
+
+	return takeByTopologyNUMAPacked(p.topology, availableCPUs, numCPUs, cpuSortingStrategy, p.options.PreferAlignByUncoreCacheOption)
 }
 
 func (p *staticPolicy) GetTopologyHints(s state.State, pod *v1.Pod, container *v1.Container) map[string][]topologymanager.TopologyHint {