trie: swap out the pools in StackTrie with an arena allocator

common/arena.go

@@ -0,0 +1,61 @@
+// Copyright 2025 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package common
+
+// Arena is an allocation primitive that allows individual allocations
+// out of a page of items and bulk de-allocations of last N allocations.
+// The most common way of using an Arena is to pair it up with a sync.Pool
+// of pages.
+type Arena[T any] struct {
+	used  uint32
+	pages [][]T
+
+	PageSize    uint32
+	NewPage     func() any
+	ReleasePage func(any)
+}
+
+// Alloc returns the next free item on the arena
+// Allocates a new page if needed
+func (a *Arena[T]) Alloc() *T {
+	pageIndex := a.used / a.PageSize
+	pageOffset := a.used % a.PageSize
+	if pageOffset == 0 {
+		a.pages = append(a.pages, a.NewPage().([]T))
+	}
+	a.used++
+	return &a.pages[pageIndex][pageOffset]
+}
+
+// Used returns the number of items that live on this arena
+func (a *Arena[T]) Used() uint32 {
+	return a.used
+}
+
+// Reset rollsback the active set of live elements to the given number
+func (a *Arena[T]) Reset(to uint32) {
+	a.used = to
+}
+
+// Release releases all the pages that the arena currently owns
+func (a *Arena[T]) Release() {
+	for _, page := range a.pages {
+		a.ReleasePage(page)
+	}
+	a.pages = nil
+	a.used = 0
+}