include::sample[dir="snippets/initScripts/multiVersionCacheRetention/groovy",files="gradleUserHome/init.d/gradle8/cache-settings.gradle"]
====

[[dir:gradle_user_home:cache_marking]]
=== Cache marking
Beginning with Gradle version 8.1, Gradle supports marking caches with a `CACHEDIR.TAG` file.

It follows the format described in https://bford.info/cachedir/[the Cache Directory Tagging Specification].

// is stored on the bit corresponding to the first word of the marked
// allocation.
type checkmarksMap struct {
	_ sys.NotInHeap
	b [heapArenaBytes / goarch.PtrSize / 8]uint8
}

// If useCheckmark is true, marking of an object uses the checkmark
// bits instead of the standard mark bits.
var useCheckmark = false

// startCheckmarks prepares for the checkmarks phase.
//
// The world must be stopped.
func startCheckmarks() {

	if err != nil {
		if xnet.IsNetworkOrHostDown(err, expectTimeouts) {
			if !c.NoMetrics {
				atomic.AddUint64(&globalStats.errs, 1)
			}
			if c.MarkOffline(err) {
				logger.LogOnceIf(ctx, logSubsys, fmt.Errorf("Marking %s offline temporarily; caused by %w", c.url.Host, err), c.url.Host)
			}
		}
		return nil, &NetworkError{err}
	}

	// If trace is enabled, dump http request and response,

		// its P's next findRunnableGCWorker.

		gcBgMarkWorkerCount++
	}
}

// gcBgMarkPrepare sets up state for background marking.
// Mutator assists must not yet be enabled.
func gcBgMarkPrepare() {
	// Background marking will stop when the work queues are empty
	// and there are no more workers (note that, since this is
	// concurrent, this may be a transient state, but mark

	drainCheckThreshold = 100000

	// pagesPerSpanRoot indicates how many pages to scan from a span root
	// at a time. Used by special root marking.
	//
	// Higher values improve throughput by increasing locality, but
	// increase the minimum latency of a marking operation.
	//
	// Must be a multiple of the pageInUse bitmap element size and
	// must also evenly divide pagesPerArena.
	pagesPerSpanRoot = 512
)

	if cfg.EnableIPv6 {
		families = append(families, unix.AF_INET6)
	}
	for _, family := range families {
		// Equiv:
		// ip rule add fwmark 0x111/0xfff pref 32764 lookup 100
		//
		// Adds in-pod rules for marking packets with the istio-specific TPROXY mark.
		// A very similar mechanism is used for sidecar TPROXY.
		//
		// TODO largely identical/copied from tools/istio-iptables/pkg/capture/run_linux.go

                    LOGGER.debug("Marking daemon stopped due to {}. The daemon is not running a build", reason);
                    stopReason = reason;
                    setState(State.Stopped);
                    break;
                case Busy:
                case Canceled:
                case Broken:
                case StopRequested:

		})

	// PollImmediate will return "timed out waiting for the condition" if the function it
	// invokes never returns true
	if err != nil {
		klog.V(2).InfoS("Failed all attempts to dial the socket so marking it as a non-Unix Domain socket. Last socket error along with the error from PollImmediate follow",
			"filePath", filePath, "lastSocketErr", lastSocketErr, "err", err)
		return false, nil
	}
	return true, nil
}

  // observed to be megamorphic once stay megamorphic forever.
  if (!stats->is_megamorphic &&
      ShouldBeMegamorphic(stats->compile_count, stats->execution_count)) {
    VLOG(1) << "Marking " << function.name()
            << " as megamorphic, compile_count=" << stats->compile_count
            << " execution_count=" << stats->execution_count;
    stats->is_megamorphic = true;
  }
}

//         *slot = ptr
//
// slot is the destination in Go code.
// ptr is the value that goes into the slot in Go code.
//
// Shade indicates that it has seen a white pointer by adding the referent
// to wbuf as well as marking it.
//
// The two shades and the condition work together to prevent a mutator
// from hiding an object from the garbage collector:
//
// 1. shade(*slot) prevents a mutator from hiding an object by moving