Disk cache: Add a histogram to measure the latency of...

net/disk_cache/entry_impl.cc

Index: net/disk_cache/entry_impl.cc
===================================================================
--- net/disk_cache/entry_impl.cc	(revision 24800)
+++ net/disk_cache/entry_impl.cc	(working copy)
@@ -29,7 +29,7 @@
  public:
   SyncCallback(disk_cache::EntryImpl* entry, net::IOBuffer* buffer,
                net::CompletionCallback* callback )
-      : entry_(entry), callback_(callback), buf_(buffer) {
+      : entry_(entry), callback_(callback), buf_(buffer), start_(Time::Now()) {
     entry->AddRef();
     entry->IncrementIoCount();
   }
@@ -41,15 +41,18 @@
   disk_cache::EntryImpl* entry_;
   net::CompletionCallback* callback_;
   scoped_refptr<net::IOBuffer> buf_;
+  Time start_;
 
   DISALLOW_EVIL_CONSTRUCTORS(SyncCallback);
 };
 
 void SyncCallback::OnFileIOComplete(int bytes_copied) {
   entry_->DecrementIoCount();
+  if (callback_) {
+    entry_->ReportIOTime(disk_cache::EntryImpl::kAsyncIO, start_);
+    callback_->Run(bytes_copied);
+  }
   entry_->Release();
-  if (callback_)
-    callback_->Run(bytes_copied);
   delete this;
 }
 
@@ -880,6 +883,9 @@
     case kSparseWrite:
       CACHE_UMA(AGE_MS, "SparseWriteTime", 0, start);
       break;
+    case kAsyncIO:
+      CACHE_UMA(AGE_MS, "AsyncIOTime", group, start);
+      break;
     default:
       NOTREACHED();
   }