Add a type for modeling multiple-dimensional gas

arbitrum/multigas/constraint.go

@@ -0,0 +1,44 @@
+package multigas
+
+import "time"
+
+// Constraint defines the max gas target per second for the given period for a single resource.
+type constraint struct {
+	period time.Duration
+	target uint64
+}
+
+// ResourceConstraints is a set of constraints for all resources.
+//
+// The chain owner defines constraints to limit the usage of each resource. A resource can have
+// multiple constraints with different periods, but there may be a single constraint given the
+// resource and period.
+//
+// Example constraints:
+// - X amount of computation over 12 seconds so nodes can keep up.
+// - Y amount of computation over 7 days so fresh nodes can catch up with the chain.
+// - Z amount of history growth over one month to avoid bloat.
+type ResourceConstraints map[ResourceKind]map[uint32]constraint
+
+func NewResourceConstraints() ResourceConstraints {
+	c := ResourceConstraints{}
+	for resource := ResourceKind(0); resource < NumResourceKind; resource++ {
+		c[resource] = map[uint32]constraint{}
+	}
+	return c
+}
+
+// SetConstraint adds or updates the given resource constraint.
+func (rc ResourceConstraints) SetConstraint(
+	resource ResourceKind, periodSecs uint32, targetPerPeriod uint64,
+) {
+	rc[resource][periodSecs] = constraint{
+		period: time.Duration(periodSecs) * time.Second,
+		target: targetPerPeriod / uint64(periodSecs),
+	}
+}
+
+// ClearConstraint removes the given resource constraint.
+func (rc ResourceConstraints) ClearConstraint(resource ResourceKind, periodSecs uint32) {
+	delete(rc[resource], periodSecs)
+}

arbitrum/multigas/constraint_test.go

@@ -0,0 +1,66 @@
+package multigas
+
+import (
+	"testing"
+	"time"
+)
+
+func TestResourceConstraints(t *testing.T) {
+	rc := NewResourceConstraints()
+
+	const (
+		minuteSecs = 60
+		daySecs    = 24 * 60 * 60
+		weekSecs   = 7 * daySecs
+		monthSecs  = 30 * daySecs
+	)
+
+	// Adds a few constraints
+	rc.SetConstraint(ResourceKindComputation, minuteSecs, 5_000_000*minuteSecs)
+	rc.SetConstraint(ResourceKindComputation, weekSecs, 3_000_000*weekSecs)
+	rc.SetConstraint(ResourceKindHistoryGrowth, monthSecs, 1_000_000*monthSecs)
+	if len(rc[ResourceKindComputation]) != 2 {
+		t.Fatalf("expected 2 computation constraints")
+	}
+	if rc[ResourceKindComputation][minuteSecs].period != time.Duration(minuteSecs)*time.Second {
+		t.Errorf("wrong constraint period")
+	}
+	if rc[ResourceKindComputation][minuteSecs].target != 5_000_000 {
+		t.Errorf("wrong constraint target")
+	}
+	if rc[ResourceKindComputation][weekSecs].period != time.Duration(weekSecs)*time.Second {
+		t.Errorf("wrong constraint period")
+	}
+	if rc[ResourceKindComputation][weekSecs].target != 3_000_000 {
+		t.Errorf("wrong constraint target")
+	}
+	if len(rc[ResourceKindHistoryGrowth]) != 1 {
+		t.Fatalf("Expected 1 history growth constraints")
+	}
+	if rc[ResourceKindHistoryGrowth][monthSecs].period != time.Duration(monthSecs)*time.Second {
+		t.Errorf("wrong constraint period")
+	}
+	if rc[ResourceKindHistoryGrowth][monthSecs].target != 1_000_000 {
+		t.Errorf("wrong constraint target")
+	}
+
+	// Updates a constraint
+	rc.SetConstraint(ResourceKindHistoryGrowth, monthSecs, 500_000*monthSecs)
+	if len(rc[ResourceKindHistoryGrowth]) != 1 {
+		t.Fatalf("Expected 1 history growth constraints")
+	}
+	if rc[ResourceKindHistoryGrowth][monthSecs].target != 500_000 {
+		t.Errorf("wrong constraint target")
+	}
+
+	// Clear constraints
+	rc.ClearConstraint(ResourceKindComputation, minuteSecs)
+	rc.ClearConstraint(ResourceKindComputation, weekSecs)
+	rc.ClearConstraint(ResourceKindHistoryGrowth, monthSecs)
+	if len(rc[ResourceKindComputation]) != 0 {
+		t.Fatalf("Expected 0 computation constraints")
+	}
+	if len(rc[ResourceKindHistoryGrowth]) != 0 {
+		t.Fatalf("Expected 0 history growth constraints")
+	}
+}

arbitrum/multigas/doc.go

@@ -0,0 +1,7 @@
+// Package multigas defines multi-dimensional gas for the EVM.
+//
+// This package introduces mechanisms to track each resource used by the EVM separately. The
+// possible resources are computation, history growth, storage access, and storage growth. By
+// tracking each one individually and setting specific constraints, we can increase the overall gas
+// target for the chain.
+package multigas

arbitrum/multigas/resources.go

@@ -0,0 +1,15 @@
+package multigas
+
+// ResourceKind represents a dimension for the multi-dimensional gas.
+type ResourceKind uint8
+
+const (
+	ResourceKindComputation ResourceKind = iota
+	ResourceKindHistoryGrowth
+	ResourceKindStorageAccess
+	ResourceKindStorageGrowth
+	NumResourceKind
+)
+
+// MultiGas tracks gas for each resource separately.
+type MultiGas [NumResourceKind]uint64