Register Overlay size dynamic counters

Summary:
## Context:
Previously, we added counters for all the operations in Overlay. However, we don't have any counter to show the size of the files and trees in Overlay. Like what we have for `inode`, we can add new dynamic counters are report size of Overlay per mounted repo.

## This diff:
This diff register the dynamic call backs. However we also need to add ` OVERLAY_DIR_COUNT` and `OVERLAY_FILE_COUNT` then `EdenMount::getCounterName` can return correct name for these counters.

Reviewed By: jdelliot

Differential Revision: D62987495

fbshipit-source-id: 98ef5b050ce03826c54d63b4556c279946dd6eaa

eden/fs/inodes/EdenMount.cpp

@@ -2061,6 +2061,10 @@ std::string EdenMount::getCounterName(CounterName name) {
  case CounterName::PERIODIC_UNLINKED_INODE_UNLOAD:
  return folly::to<std::string>(
  "inodemap.", base, ".unloaded_unlinked_inodes");
+ case CounterName::OVERLAY_DIR_COUNT:
+ return folly::to<std::string>("overlay.", base, ".dir_count");
+ case CounterName::OVERLAY_FILE_COUNT:
+ return folly::to<std::string>("overlay.", base, ".file_count");
  }
  EDEN_BUG() << "unknown counter name "
  << static_cast<std::underlying_type_t<CounterName>>(name);

eden/fs/inodes/EdenMount.h

@@ -202,7 +202,17 @@ enum class CounterName {
  * unlinked inode unloading. This is used on NFS mounts to clean up old
  * inodes.
  */
- PERIODIC_UNLINKED_INODE_UNLOAD
+ PERIODIC_UNLINKED_INODE_UNLOAD,
+
+ /**
+ * Represents the number of directories that were materialized in the overlay.
+ */
+ OVERLAY_DIR_COUNT,
+
+ /**
+ * Represents the number of files that were materialized in the overlay.
+ */
+ OVERLAY_FILE_COUNT
 
 };
 

eden/fs/inodes/Overlay.cpp

@@ -758,6 +758,10 @@ OverlayFile Overlay::createOverlayFile(
 
 #endif // !_WIN32
 
+Overlay::InternalOverlayStats Overlay::getOverlayStats() const {
+ return *overlayStats_.rlock();
+}
+
 InodeNumber Overlay::getMaxInodeNumber() {
  auto ino = nextInodeNumber_.load(std::memory_order_relaxed);
  XCHECK_GT(ino, 1u);

eden/fs/inodes/Overlay.h

@@ -260,6 +260,11 @@ class Overlay : public std::enable_shared_from_this<Overlay> {
  size_t fileCount{0};
  };
 
+ /**
+ * Get stats about how many objects are materialized in Overlay.
+ */
+ InternalOverlayStats getOverlayStats() const;
+
  void addChild(
  InodeNumber parent,
  const std::pair<PathComponent, DirEntry>& childEntry,

eden/fs/service/EdenServer.cpp

@@ -1483,6 +1483,16 @@ void EdenServer::registerStats(std::shared_ptr<EdenMount> edenMount) {
  auto stats = edenMount->getJournal().getStats();
  return stats ? stats->maxFilesAccumulated : 0;
  });
+ counters->registerCallback(
+ edenMount->getCounterName(CounterName::OVERLAY_DIR_COUNT), [edenMount] {
+ auto stats = edenMount->getOverlay()->getOverlayStats();
+ return stats.dirCount;
+ });
+ counters->registerCallback(
+ edenMount->getCounterName(CounterName::OVERLAY_FILE_COUNT), [edenMount] {
+ auto stats = edenMount->getOverlay()->getOverlayStats();
+ return stats.fileCount;
+ });
 #ifndef _WIN32
  if (auto* channel = edenMount->getFuseChannel()) {
  for (auto metric : RequestMetricsScope::requestMetrics) {
@@ -1533,6 +1543,10 @@ void EdenServer::unregisterStats(EdenMount* edenMount) {
  edenMount->getCounterName(CounterName::JOURNAL_DURATION));
  counters->unregisterCallback(
  edenMount->getCounterName(CounterName::JOURNAL_MAX_FILES_ACCUMULATED));
+ counters->unregisterCallback(
+ edenMount->getCounterName(CounterName::OVERLAY_DIR_COUNT));
+ counters->unregisterCallback(
+ edenMount->getCounterName(CounterName::OVERLAY_FILE_COUNT));
 #ifndef _WIN32
  if (edenMount->getFuseChannel()) {
  for (auto metric : RequestMetricsScope::requestMetrics) {