Bug 592422 - preallocate individual (non-block) cache files. r=jduell,taras a=b

netwerk/cache/nsDiskCacheMap.h

@@ -94,6 +94,9 @@ struct nsDiskCacheEntry;
 #define kMaxDataFileSize   5 * 1024 * 1024  // 5 MB (in bytes) 
 #define kBuckets           (1 << 5)    // must be a power of 2!
 
+// preallocate up to 1MB of separate cache file
+#define kPreallocateLimit  1 * 1024 * 1024
+
 class nsDiskCacheRecord {
 
 private:

netwerk/cache/nsDiskCacheStreams.cpp

@@ -43,6 +43,7 @@
 #include "nsDiskCacheDevice.h"
 #include "nsDiskCacheStreams.h"
 #include "nsCacheService.h"
+#include "mozilla/FileUtils.h"
 
 
 
@@ -728,6 +729,10 @@ nsDiskCacheStreamIO::FlushBufferToFile()
         // allocate file
         rv = OpenCacheFile(PR_RDWR | PR_CREATE_FILE, &mFD);
         if (NS_FAILED(rv))  return rv;
+
+        PRInt64 dataSize = mBinding->mCacheEntry->PredictedDataSize();
+        if (dataSize != -1)
+            mozilla::fallocate(mFD, PR_MIN(dataSize, kPreallocateLimit));
     }
     
     // write buffer

xpcom/glue/FileUtils.cpp

@@ -47,10 +47,12 @@
 #include "nscore.h"
 #include "private/pprio.h"
 #include "mozilla/FileUtils.h"
+#include "mozilla/FunctionTimer.h"
 
 bool 
 mozilla::fallocate(PRFileDesc *aFD, PRInt64 aLength) 
 {
+  NS_TIME_FUNCTION;
 #if defined(HAVE_POSIX_FALLOCATE)
   return posix_fallocate(PR_FileDesc2NativeHandle(aFD), 0, aLength) == 0;
 #elif defined(XP_WIN)