Abstract: A method, system, and program for improving free item distribution among multiple free lists during garbage collection for more efficient object allocation are provided. A garbage collector predicts future allocation requirements and then distributes free items to multiple subpool free lists and a TLH free list during the sweep phase according to the future allocation requirements. The sizes of subpools and number of free items in subpools are predicted as the most likely to match future allocation requests. In particular, once a subpool free list is filled with the number of free items needed according to the future allocation requirements, any additional free items designated for the subpool free list can be divided into multiple TLH sized free items and placed on the TLH free list. Allocation threads are enabled to acquire free items from the TLH free list and to replenish a current TLH without acquiring heap lock.

Abstract: A method, system, and program for efficient parallel bitwise sweeps of larger objects during garbage collection are provided. During a bitwise sweep, a helper thread scans a mark vector looking for a consecutive sequence of unmarked bits of a sufficient length following a marked bit. Once a consecutive sequence of unmarked bits of a sufficient length following a marked bit is detected, the helper thread fetches the size of a marked object corresponding to the marked bit. If the size of the marked object exceeds a size represented by the consecutive sequence of unmarked bits, the remainder of the bits representing the marked object are skipped, such that once a marked object is identified as potentially exceeding an object fetch threshold the helper thread efficiently skips the remainder of the bits represents the marked object and continues scanning for a number of consecutive zeroes indicating free space.

Abstract: A method, system, and program for improving free item distribution among multiple free lists during garbage collection for more efficient object allocation are provided. A garbage collector predicts future allocation requirements and then distributes free items to multiple subpool free lists and a TLH free list during the sweep phase according to the future allocation requirements. The sizes of subpools and number of free items in subpools are predicted as the most likely to match future allocation requests. In particular, once a subpool free list is filled with the number of free items needed according to the future allocation requirements, any additional free items designated for the subpool free list can be divided into multiple TLH sized free items and placed on the TLH free list. Allocation threads are enabled to acquire free items from the TLH free list and to replenish a current TLH without acquiring heap lock.

Abstract: A method, system, and program for assigning sections within a memory heap for efficient garbage collection of large objects are provided. A first portion of a memory heap is distributed among a first number of sections from among multiple sections, wherein the first number of sections correspond to a number of helper threads allocable for bitwise sweeping of the memory heap during garbage collection. A section portion of the memory heap is distribution among a second number of sections, wherein a size of the memory heap distribution of the second number of sections progressively decreases, such that the total number of sections within the memory is minimized, but any disparity between each of the helper threads completing sweeps of all the sections is reduced.

Abstract: Host page management assist functions are employed to manage storage of a pageable mode virtual environment. These functions enable storage to be managed by a processor of the environment absent intervention of a host of the environment. The functions include a resolve host page function; a pin function; and unpin functions.