JVM '02 Abstract
Concurrent Remembered Set Refinement in Generational Garbage Collection
David Detlefs, Ross Knippel, Sun Microsystems, William D. Clinger, Northeastern University, Matthias Jacob, Department of Computer Science, Princeton University
Generational garbage collection divides a heap up into two or more
generations, and usually collects a youngest generation most frequently.
Collection of the youngest generation requires identification of
pointers into that generation from older generations; a data structure
that supports such identification is called a remembered set.
Various remembered set mechanisms have been proposed; these generally
require mutator code to execute a write barrier when modifying
pointer fields. Remembered set data structures can vary in their
precision: an imprecise structure requires the garbage collector to
do more work to find old-to-young pointers. Generally there is a
tradeoff between remembered set precision and barrier cost: a more
precise remembered set requires a more elaborate barrier. Many
current systems tend to favor more efficient barriers in this
tradeoff, as shown by the widespread popularity of relatively
imprecise card marking techniques.
This imprecision becomes increasingly costly as the ratio between
old- and young-generation sizes grows. We propose a technique that
maintains more precise remembered sets that scale
with old-generation size, using a barrier whose cost is not
significantly greater than card marking.
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