Changes between Version 1 and Version 2 of MemoryUtils

Timestamp:

Mar 25, 2010, 11:32:05 PM (10 years ago)

Author:

gz

Comment:

document idom-heap-utilization

MemoryUtils

@@ -124 +124 @@
 
 [Function][[BR]]
+'''idom-heap-utilization''' `&key unit (sort :size) (threshold 0.01) (area :tenured)`
+
+This function analyzes the core file heap based on dominance.  It takes a while
+to compute, but often gives more meaningful results than the regular heap
+utilization report, especially when looking at memory leaks.
+
+An object A is said to ''dominate'' another object B if all paths from gc roots
+to B go through A.  A is said to ''immediately dominate'' B if A dominates B and
+every other object that dominates B also dominates A.
+
+Since an object can only have one immediate dominator, all objects that are not
+dominators themselves can be partitioned into disjoint sets, each consisting of
+all objects with the same immediate dominator.
+
+If B is in the partition owned by A, i.e. B is not a dominator of anything and
+is immediately dominated by A, then for all intents and purposes, B is just a
+part of A: B will be garbage collected whenever A is garbage collected, and there
+are no pointers directly to B from outside the partition.  Nothing about the behavior
+of the heap would change if B was permanently appended to A instead of being a
+separate object.
+
+`idom-heap-utilization` attributes the total size of all the partition members
+to the immediate dominator.  I.e. it computes what `core-heap-utilization` would report
+if the heap was flattened by attaching all objects to their immediate dominators,
+and ignoring all types except the type of the immediate dominator.  This
+tends to emphasize the types of objects that are really responsible for the memory usage.
+
+
+[Function][[BR]]
 '''core-print-call-history''' `&key (stream t) origin detailed-p`