// output to a writer during profiling.
//
// # Heap profile
//
// The heap profile reports statistics as of the most recently completed
// garbage collection; it elides more recent allocation to avoid skewing
// the profile away from live data and toward garbage.
// If there has been no garbage collection at all, the heap profile reports
// all known allocations. This exception helps mainly in programs running

	// Experimental heap span events. Added in Go 1.23.
	EvSpan      // heap span exists [timestamp, id, npages, type/class]
	EvSpanAlloc // heap span alloc [timestamp, id, npages, type/class]
	EvSpanFree  // heap span free [timestamp, id]

	// Experimental heap object events. Added in Go 1.23.
	EvHeapObject      // heap object exists [timestamp, id, type]
	EvHeapObjectAlloc // heap object alloc [timestamp, id, type]

//   - gc=N (heap profile): N > 0: run a garbage collection cycle before profiling
//   - seconds=N (allocs, block, goroutine, heap, mutex, threadcreate profiles): return a delta profile
//   - seconds=N (cpu (profile), trace profiles): profile for the given duration
//
// # Usage examples
//
// Use the pprof tool to look at the heap profile:
//
//	go tool pprof http://localhost:6060/debug/pprof/heap

		case "/memory/classes/heap/objects:bytes":
			objects.totalBytes = samples[i].Value.Uint64()
		case "/gc/heap/objects:objects":
			objects.total = samples[i].Value.Uint64()
		case "/gc/heap/allocs:bytes":
			objects.allocdBytes = samples[i].Value.Uint64()
		case "/gc/heap/allocs:objects":
			objects.allocs = samples[i].Value.Uint64()
		case "/gc/heap/allocs-by-size:bytes":

				return
			}
		}
		t.Errorf("len(C) = %d, want 1", n)
	}

	// Test simple stop; timer never in heap.
	tim.Stop()
	noTick()

	// Test modify of timer not in heap.
	tim.Reset(10000 * Second)
	noTick()

	if synctimerchan {
		// Test modify of timer in heap.
		tim.Reset(1)
		Sleep(sched)
		if l, c := len(C), cap(C); l != 0 || c != 0 {

// Each chunk must be a multiple of the heap arena size, or the heap arena size must
// be divisible by the arena chunks. The address space for each chunk, and each
// corresponding heapArena for that address space, are eternally reserved for use as
// arena chunks. That is, they can never be used for the general heap. Each chunk
// is also represented by a single mspan, and is modeled as a single large heap

	// span in the heap were stored in this set, and each span were
	// the minimum size (1 runtime page, 8 KiB), then roughly the
	// smallest heap which would be unrepresentable is 32 TiB in size.
	index atomicHeadTailIndex
}

const (
	spanSetBlockEntries = 512 // 4KB on 64-bit
	spanSetInitSpineCap = 256 // Enough for 1GB heap on 64-bit
)

type spanSetBlock struct {

//   but is critical when allocating new spans. The entry point for
//   this is mheap_.reclaim and it's driven by a sequential scan of
//   the page marks bitmap in the heap arenas.
//
// Both algorithms ultimately call mspan.sweep, which sweeps a single
// heap span.

package runtime

import (
	"internal/abi"
	"internal/runtime/atomic"
	"unsafe"
)

var sweep sweepdata

// State of background sweep.

Daemons use the JVM's default minimum heap size.

If the requested build environment does not specify a maximum heap size, the Daemon uses up to 512MB of heap.
512MB is adequate for most builds.
Larger builds with hundreds of subprojects, configuration, and source code may benefit from a larger heap size.

[[sec:status]]
== Check Daemon status

In general, types that are allocated using any of these should be
marked as not in heap by embedding `runtime/internal/sys.NotInHeap`.

Objects that are allocated in unmanaged memory **must not** contain
heap pointers unless the following rules are also obeyed:

1. Any pointers from unmanaged memory to the heap must be garbage
   collection roots. More specifically, any pointer must either be