diff --git a/mozilla/js/src/xpconnect/loader/mozJSComponentLoader.cpp b/mozilla/js/src/xpconnect/loader/mozJSComponentLoader.cpp
index 44c8a500be8..f4cb868e604 100644
--- a/mozilla/js/src/xpconnect/loader/mozJSComponentLoader.cpp
+++ b/mozilla/js/src/xpconnect/loader/mozJSComponentLoader.cpp
@@ -99,13 +99,13 @@ static const char kObserverServiceContractID[] = "@mozilla.org/observer-service;
 
 /**
  * Buffer sizes for serialization and deserialization of scripts.
- * These should be tuned at some point.
+ * FIXME: bug #411579 (tune this macro!) Last updated: Jan 2008
  */
 #define XPC_SERIALIZATION_BUFFER_SIZE   (64 * 1024)
-#define XPC_DESERIALIZATION_BUFFER_SIZE (8 * 1024)
+#define XPC_DESERIALIZATION_BUFFER_SIZE (12 * 8192)
 
 // Inactivity delay before closing our fastload file stream.
-static const int kFastLoadWriteDelay = 5000;   // 5 seconds
+static const int kFastLoadWriteDelay = 10000;   // 10 seconds
 
 #ifdef PR_LOGGING
 // NSPR_LOG_MODULES=JSComponentLoader:5
diff --git a/mozilla/modules/libpref/src/nsPrefService.cpp b/mozilla/modules/libpref/src/nsPrefService.cpp
index fee1de3c45c..27ad9cddf32 100644
--- a/mozilla/modules/libpref/src/nsPrefService.cpp
+++ b/mozilla/modules/libpref/src/nsPrefService.cpp
@@ -50,6 +50,7 @@
 #include "nsCRT.h"
 #include "nsCOMArray.h"
 #include "nsXPCOMCID.h"
+#include "nsAutoPtr.h"
 
 #include "nsQuickSort.h"
 #include "prmem.h"
@@ -68,7 +69,6 @@
 
 // Definitions
 #define INITIAL_PREF_FILES 10
-#define PREF_READ_BUFFER_SIZE 4096
 
 // Prototypes
 #ifdef MOZ_PROFILESHARING
@@ -586,7 +586,6 @@ static PRBool isSharingEnabled()
 static nsresult openPrefFile(nsIFile* aFile)
 {
   nsCOMPtr<nsIInputStream> inStr;
-  char      readBuf[PREF_READ_BUFFER_SIZE];
 
 #if MOZ_TIMELINE
   {
@@ -600,21 +599,33 @@ static nsresult openPrefFile(nsIFile* aFile)
   if (NS_FAILED(rv)) 
     return rv;        
 
+  PRInt64 fileSize;
+  rv = aFile->GetFileSize(&fileSize);
+  if (NS_FAILED(rv))
+    return rv;
+
+  nsAutoArrayPtr<char> fileBuffer(new char[fileSize]);
+  if (fileBuffer == nsnull)
+    return NS_ERROR_OUT_OF_MEMORY;
+
   PrefParseState ps;
   PREF_InitParseState(&ps, PREF_ReaderCallback, NULL);
+
+  // Read is not guaranteed to return a buf the size of fileSize,
+  // but usually will.
   nsresult rv2 = NS_OK;
   for (;;) {
     PRUint32 amtRead = 0;
-    rv = inStr->Read(readBuf, sizeof(readBuf), &amtRead);
+    rv = inStr->Read((char*)fileBuffer, fileSize, &amtRead);
     if (NS_FAILED(rv) || amtRead == 0)
       break;
-
-    if (!PREF_ParseBuf(&ps, readBuf, amtRead)) {
+    if (!PREF_ParseBuf(&ps, fileBuffer, amtRead))
       rv2 = NS_ERROR_FILE_CORRUPTED;
-    }
   }
+
   PREF_FinalizeParseState(&ps);
-  return NS_FAILED(rv) ? rv : rv2;        
+
+  return NS_FAILED(rv) ? rv : rv2;
 }
 
 /*
diff --git a/mozilla/xpcom/io/nsFastLoadFile.cpp b/mozilla/xpcom/io/nsFastLoadFile.cpp
index 323b198ebad..1c62e8f301c 100644
--- a/mozilla/xpcom/io/nsFastLoadFile.cpp
+++ b/mozilla/xpcom/io/nsFastLoadFile.cpp
@@ -630,9 +630,9 @@ nsFastLoadFileReader::SetInputStream(nsIInputStream *aInputStream)
 }
 
 /**
- * XXX tuneme
+ * FIXME: bug #411579 (tune this macro!) Last updated: Jan 2008
  */
-#define MFL_CHECKSUM_BUFSIZE    8192
+#define MFL_CHECKSUM_BUFSIZE    (6 * 8192)
 
 NS_IMETHODIMP
 nsFastLoadFileReader::ComputeChecksum(PRUint32 *aResult)