[Help-smalltalk] faster startup 7/n

[Paolo Bonzini]

VFS was a hog not only when quitting, but also on startup.  This simple 
patch brings hello-world time down to 58ms (without copy-on-write) and 
42ms (with).

Of these, about 8ms are spent in the last remaining call to 
allSubinstancesDo: (in FileDescriptor), but I don't see an easy way to 
remove it or to make it faster.  The remaining 50ms/34ms are the sheer 
startup time.

Paolo

--- orig/kernel/VFS.st
+++ mod/kernel/VFS.st
@@ -228,10 +228,7 @@ update: aspect
      filesystems specified by the subclasses upon image load."
 
     (aspect == #returnFromSnapshot or: [ aspect == #finishedSnapshot ]) 
ifTrue: [
-       Registry := LookupTable new.
-       self allSubclassesDo: [ :each |
-           each fileSystems do: [ :fs | self register: fs forClass: each ]
-       ]
+       Registry := nil.
     ].
     (aspect == #aboutToQuit or: [ aspect == #aboutToSnapshot ]) ifTrue: [
        self allSubclassesDo: [ :each | each release ].
@@ -262,6 +259,10 @@ vfsFor: fileName name: fsName subPath: s
     "Create an instance of a subclass of the receiver, implementing the virtual
      file `subPath' inside the `fileName' archive.  fsName is the virtual
      filesystem name and is used to determine the subclass to be instantiated."
+    Registry isNil ifTrue: [
+       Registry := LookupTable new.
+       self allSubclassesDo: [ :each |
+           each fileSystems do: [ :fs | self register: fs forClass: each ] ] ].
     ^(Registry at: fsName) 
        vfsFor: fileName name: fsName subPath: subPath!