mktables memory reduction

Does the attached patch make sense? It lowers RAM and CPU usage by about 10%
on Linux, and 6% on FreeBSD.

Nicholas Clark

>From fe46bd796c282f6a6e4793afaf847e04d3be3524 Mon Sep 17 00:00:00 2001
From: Nicholas Clark <nick@ccl4.org>
Date: Mon, 7 May 2012 09:58:13 +0200
Subject: [PATCH] In mktables, lazily compute the 'standard_form' for Ranges.

Instead of calculating the standard form up front, calculate it only when
needed and cache the result. There are 368676 non-special objects, but
the standard form is only requested for 22047 of them. For the systems I
tested on, this reduces RAM and CPU usage by about 10% on Linux, and 6% on
FreeBSD.

This is more significant than it may first seem, because mktables is the
largest RAM user of anything run during the build process, so this reduces
the build process peak RAM requirement.

1 files changed, 9 insertions, 7 deletions

diff --git a/lib/unicore/mktables b/lib/unicore/mktables
index def260aa12..559c519639 100644
--- a/lib/unicore/mktables
+++ b/lib/unicore/mktables
@@ -2921,10 +2921,6 @@ sub trace { return main::trace(@_); }
 
         Carp::carp_extra_args(\%args) if main::DEBUG && %args;
 
-        if (! $type{$addr}) {
-            $standard_form{$addr} = main::standardize($value);
-        }
-
         return $self;
     }
 
@@ -2954,8 +2950,11 @@ sub trace { return main::trace(@_); }
     }
 
     sub standard_form {
-        # The standard form is the value itself if the standard form is
-        # undefined (that is if the value is special)
+        # Calculate the standard form only if needed, and cache the result.
+        # The standard form is the value itself if the type is special.
+        # This represents a considerable CPU and memory saving - at the time
+        # of writing there are 368676 non-special objects, but the standard
+        # form is only requested for 22047 of them - ie about 6%.
 
         my $self = shift;
         Carp::carp_extra_args(\@_) if main::DEBUG && @_;
@@ -2963,7 +2962,10 @@ sub trace { return main::trace(@_); }
         my $addr = do { no overloading; pack 'J', $self; };
 
         return $standard_form{$addr} if defined $standard_form{$addr};
-        return $value{$addr};
+
+        my $value = $value{$addr};
+        return $value if $type{$addr};
+        return $standard_form{$addr} = main::standardize($value);
     }
 
     sub dump {