Add UMA stats for ExtensionCache

Reported metrics:
- number of extensions in cache
- size of cache on disk

BUG=316371
TEST=manual

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=247760

Review URL: https://codereview.chromium.org/148013004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248046 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 50 insertions, 7 deletions

diff --git a/chrome/browser/extensions/updater/extension_cache_impl.cc b/chrome/browser/extensions/updater/extension_cache_impl.cc
index ddf0cd2..53addd5 100644
--- a/chrome/browser/extensions/updater/extension_cache_impl.cc
+++ b/chrome/browser/extensions/updater/extension_cache_impl.cc
@@ -6,6 +6,7 @@
 
 #include "base/bind.h"
 #include "base/memory/singleton.h"
+#include "base/metrics/histogram.h"
 #include "base/sequenced_task_runner.h"
 #include "base/stl_util.h"
 #include "base/threading/sequenced_worker_pool.h"
@@ -104,6 +105,15 @@ void ExtensionCacheImpl::OnCacheInitialized() {
     it->Run();
   }
   init_callbacks_.clear();
+
+  uint64 cache_size = 0;
+  size_t extensions_count = 0;
+  if (cache_->GetStatistics(&cache_size, &extensions_count)) {
+    UMA_HISTOGRAM_COUNTS_100("Extensions.ExtensionCacheCount",
+                             extensions_count);
+    UMA_HISTOGRAM_MEMORY_MB("Extensions.ExtensionCacheSize",
+                            cache_size / (1024 * 1024));
+  }
 }
 
 void ExtensionCacheImpl::Observe(int type,
diff --git a/chrome/browser/extensions/updater/local_extension_cache.cc b/chrome/browser/extensions/updater/local_extension_cache.cc
index 7411805..b88e802 100644
--- a/chrome/browser/extensions/updater/local_extension_cache.cc
+++ b/chrome/browser/extensions/updater/local_extension_cache.cc
@@ -29,7 +29,7 @@ const char LocalExtensionCache::kCacheReadyFlagFileName[] = ".initialized";
 
 LocalExtensionCache::LocalExtensionCache(
     const base::FilePath& cache_dir,
-    size_t max_cache_size,
+    uint64 max_cache_size,
     const base::TimeDelta& max_cache_age,
     const scoped_refptr<base::SequencedTaskRunner>& backend_task_runner)
     : cache_dir_(cache_dir),
@@ -151,6 +151,21 @@ bool LocalExtensionCache::RemoveExtension(const std::string& id) {
   return true;
 }
 
+bool LocalExtensionCache::GetStatistics(uint64* cache_size,
+                                        size_t* extensions_count) {
+  if (state_ != kReady)
+    return false;
+
+  *cache_size = 0;
+  for (CacheMap::iterator it = cached_extensions_.begin();
+       it != cached_extensions_.end(); ++it) {
+    *cache_size += it->second.size;
+  }
+  *extensions_count = cached_extensions_.size();
+
+  return true;
+}
+
 void LocalExtensionCache::SetCacheStatusPollingDelayForTests(
     const base::TimeDelta& delay) {
   cache_status_polling_delay_ = delay;
@@ -425,7 +440,7 @@ void LocalExtensionCache::CleanUp() {
 
   std::vector<CacheMap::iterator> items;
   items.reserve(cached_extensions_.size());
-  size_t total_size = 0;
+  uint64_t total_size = 0;
   for (CacheMap::iterator it = cached_extensions_.begin();
        it != cached_extensions_.end(); ++it) {
     items.push_back(it);
@@ -447,7 +462,7 @@ void LocalExtensionCache::CleanUp() {
 LocalExtensionCache::CacheItemInfo::CacheItemInfo(
     const std::string& version,
     const base::Time& last_used,
-    const size_t size,
+    uint64 size,
     const base::FilePath& file_path)
     : version(version), last_used(last_used), size(size), file_path(file_path) {
 }
diff --git a/chrome/browser/extensions/updater/local_extension_cache.h b/chrome/browser/extensions/updater/local_extension_cache.h
index 604b670..63652ba 100644
--- a/chrome/browser/extensions/updater/local_extension_cache.h
+++ b/chrome/browser/extensions/updater/local_extension_cache.h
@@ -32,7 +32,7 @@ class LocalExtensionCache {
   // means that all unused cache items will be removed on Shutdown.
   // All file I/O is done via the |backend_task_runner|.
   LocalExtensionCache(const base::FilePath& cache_dir,
-                      size_t max_cache_size,
+                      uint64 max_cache_size,
                       const base::TimeDelta& max_cache_age,
                       const scoped_refptr<base::SequencedTaskRunner>&
                           backend_task_runner);
@@ -73,6 +73,10 @@ class LocalExtensionCache {
   // removed from disk too.
   bool RemoveExtension(const std::string& id);
 
+  // Return cache statistics. Returns |false| if cache is not ready.
+  bool GetStatistics(uint64* cache_size,
+                     size_t* extensions_count);
+
   bool is_ready() const { return state_ == kReady; }
   bool is_uninitialized() const { return state_ == kUninitialized; }
   bool is_shutdown() const { return state_ == kShutdown; }
@@ -84,12 +88,12 @@ class LocalExtensionCache {
   struct CacheItemInfo {
     std::string version;
     base::Time last_used;
-    int64 size;
+    uint64 size;
     base::FilePath file_path;
 
     CacheItemInfo(const std::string& version,
                   const base::Time& last_used,
-                  const size_t size,
+                  uint64 size,
                   const base::FilePath& file_path);
   };
   typedef std::map<std::string, CacheItemInfo> CacheMap;
@@ -175,7 +179,7 @@ class LocalExtensionCache {
   base::FilePath cache_dir_;
 
   // Maximum size of cache dir on disk.
-  size_t max_cache_size_;
+  uint64 max_cache_size_;
 
   // Minimal age of unused item in cache, items prior to this age will be
   // deleted on shutdown.
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index f07e767..a71c41a 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -4432,6 +4432,20 @@ other types of suffix sets.
   <summary>The time for an extension's event page to load.</summary>
 </histogram>
 
+<histogram name="Extensions.ExtensionCacheCount">
+  <summary>
+    Number of cached extensions on disk. Reported on Chrome OS during user
+    session start.
+  </summary>
+</histogram>
+
+<histogram name="Extensions.ExtensionCacheSize" units="MB">
+  <summary>
+    Total size of .crx files in cache on disk. Reported on Chrome OS during user
+    session start.
+  </summary>
+</histogram>
+
 <histogram name="Extensions.ExtensionInstalled">
   <summary>An extension has been installed.</summary>
 </histogram>