Add documentation about "non-zero requests"

Author: Jonathan Basseri

pkg/scheduler/algorithm/priorities/util/non_zero.go

@@ -26,15 +26,16 @@ import "k8s.io/api/core/v1"
 // consuming no resources whatsoever. We chose these values to be similar to the
 // resources that we give to cluster addon pods (#10653). But they are pretty arbitrary.
 // As described in #11713, we use request instead of limit to deal with resource requirements.
-
-// DefaultMilliCPURequest defines default milli cpu request number.
-const DefaultMilliCPURequest int64 = 100 // 0.1 core
-// DefaultMemoryRequest defines default memory request size.
-const DefaultMemoryRequest int64 = 200 * 1024 * 1024 // 200 MB
+const (
+	// DefaultMilliCPURequest defines default milli cpu request number.
+	DefaultMilliCPURequest int64 = 100 // 0.1 core
+	// DefaultMemoryRequest defines default memory request size.
+	DefaultMemoryRequest int64 = 200 * 1024 * 1024 // 200 MB
+)
 
 // GetNonzeroRequests returns the default resource request if none is found or
 // what is provided on the request.
-func GetNonzeroRequests(requests *v1.ResourceList) (int64, int64) {
+func GetNonzeroRequests(requests *v1.ResourceList) (milliCPU int64, memory int64) {
 	var outMilliCPU, outMemory int64
 	// Override if un-set, but not if explicitly set to zero
 	if _, found := (*requests)[v1.ResourceCPU]; !found {

pkg/scheduler/nodeinfo/node_info.go

@@ -52,11 +52,14 @@ type NodeInfo struct {
 	podsWithAffinity []*v1.Pod
 	usedPorts        HostPortInfo
 
-	// Total requested resource of all pods on this node.
-	// It includes assumed pods which scheduler sends binding to apiserver but
-	// didn't get it as scheduled yet.
+	// Total requested resources of all pods on this node. This includes assumed
+	// pods, which scheduler has sent for binding, but may not be scheduled yet.
 	requestedResource *Resource
-	nonzeroRequest    *Resource
+	// Total requested resources of all pods on this node with a minimum value
+	// applied to each container's CPU and memory requests. This does not reflect
+	// the actual resource requests for this node, but is used to avoid scheduling
+	// many zero-request pods onto one node.
+	nonzeroRequest *Resource
 	// We store allocatedResources (which is Node.Status.Allocatable.*) explicitly
 	// as int64, to avoid conversions and accessing map.
 	allocatableResource *Resource