Disk cache: More instrumentation for the cache.

Now we separate data between before and after the cache
is full. Also, reduce the rate at which a particular
client sends data to be only once a week. The effect is
that the histogram data will only have one value per client,
and the same client will not be "voting" on more than one
version (release) at the same time.


Review URL: http://codereview.chromium.org/50063

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@12218 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 13 insertions, 5 deletions

diff --git a/net/disk_cache/eviction.cc b/net/disk_cache/eviction.cc
index 6f7df82..16d0957 100644
--- a/net/disk_cache/eviction.cc
+++ b/net/disk_cache/eviction.cc
@@ -140,11 +140,19 @@ void Eviction::ReportTrimTimes(EntryImpl* entry) {
   static bool first_time = true;
   if (first_time) {
     first_time = false;
-    std::string name(StringPrintf("DiskCache.TrimAge_%d",
-                                  header_->experiment));
-    static Histogram counter(name.c_str(), 1, 10000, 50);
-    counter.SetFlags(kUmaTargetedHistogramFlag);
-    counter.Add((Time::Now() - entry->GetLastUsed()).InHours());
+    if (backend_->ShouldReportAgain()) {
+      std::string name(StringPrintf("DiskCache.TrimAge_%d",
+                                    header_->experiment));
+      static Histogram counter(name.c_str(), 1, 10000, 50);
+      counter.SetFlags(kUmaTargetedHistogramFlag);
+      counter.Add((Time::Now() - entry->GetLastUsed()).InHours());
+    }
+
+    if (header_->create_time || !header_->lru.filled) {
+      // This is the first entry that we have to evict, generate some noise.
+      header_->lru.filled = 1;
+      backend_->FirstEviction();
+    }
   }
 }