| 摘要 |
A pointer-specific instruction variant replacement mechanism facilitates an exact write barrier, i.e., a write barrier specific to pointer stores and transparent to non-pointer stores. Pointer store specific instruction replacement allows some implementations to provide an exact barrier specific to the particular set of intergenerational pointer stores that are of interest to a particular garbage collection method or combination of methods. The exact identification of pointer stores herein does not require tags encoded in-line with collected memory storage and does not require non-standard word sizes to support such tags. In one embodiment, a non-quick to quick translator cache provides pointer specific store instruction replacement. In another, self-modifying code provides pointer specific store instruction replacement. An exemplary write barrier provided in accordance with the pointer-specific instruction variant replacement mechanism of this invention affords a garbage collector implementer with support for a wide variety of garbage collection methods, including remembered set-based methods, card-marking type methods, write barrier based copying collector methods, mark-sweep methods, etc., as well as combinations thereof and combinations including train algorithm type methods to managing mature portions of a generationally collected memory space. Such a write barrier can eliminate non-pointer stores from the set of stores that are evaluated against, for example, an intergenerational pointer store trap matrix or a garbage collection page mask to determine whether or not to trap. Such a write barrier can also eliminate entries associated with non-pointer stores from remembered set or card table stores for collection time scanning of modified portions of a collected generational space.
|
