[Zodb-checkins] CVS: ZODB3/ZEO - simul.py:1.12.8.2.18.16

[Tim Peters]

Update of /cvs-repository/ZODB3/ZEO
In directory cvs.zope.org:/tmp/cvs-serv27714/ZEO

Modified Files:
      Tag: Zope-2_6-branch
	simul.py 
Log Message:
Thor:  Woo hoo!  On zope.org-main, the 50MB hit rate zooms from 44.4% to
62.1%, and at 100MB from 69.6% to 75.3%.  This comes from giving smaller
new objects higher initial worth than larger new objects.  Before, it
gave all new objects worth 0, but in steady state I think that means
a new object has a very hard time surviving (the most recent object
added is in the lowest-worth bucket then, so is a candidate for immediate
eviction).


=== ZODB3/ZEO/simul.py 1.12.8.2.18.15 => 1.12.8.2.18.16 ===
--- ZODB3/ZEO/simul.py:1.12.8.2.18.15	Fri Dec  5 12:23:22 2003
+++ ZODB3/ZEO/simul.py	Sat Dec  6 01:03:48 2003
@@ -33,6 +33,7 @@
 import time
 import getopt
 import struct
+import math
 
 from sets import Set
 
@@ -624,7 +625,7 @@
                     self.insert(oid, size)
         else:
             self.insert(oid, size)
-            
+
     def insert(self, oid, size):
         # New objects enter the cache via a1in.  If they
         # are frequently used over a long enough time, they
@@ -1587,7 +1588,11 @@
         object.linkbefore(self.currentobj)
 
         if object.worth is None:
-            object.worth = 0
+            # Give smaller objects higher initial worth.  This favors kicking
+            # out unreferenced large objects before kicking out unreferenced
+            # small objects.  On real life traces, this is a significant
+            # win for the hit rate.
+            object.worth = 32 - int(round(math.log(object.size, 2)))
         self.worthsets[object.worth].add(object)
 
     # Decrease the worth of the current object, and advance the