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The Java programming language manages memory automatically through the use of a garbage collector (GC). The Java Virtual Machine provides several GCs tuned for different usage scenarios. One such GC is ZGC. Both ZGC and other GCs utilize bump-pointer allocation, which allocates objects compactly but leads to the creation of unusable memory gaps over time, known as fragmentation. ZGC handles fragmentation through relocation, a process which is costly. This thesis proposes an alternative memory allocation method leveraging free-lists to reduce the need for relocation to manage fragmentation.We design and develop a new allocator tailored for ZGC, based on the TLSF allocator by Masmano et al. Previous research on the customization of allocators shows varying results and does not fully investigate usage in complex environments like a GC.Opportunities for enhancements in performance and memory efficiency are identified and implemented through the exploration of ZGC's operational boundaries. The most significant adaptation is the introduction of a 0-byte header, which leverages information within ZGC to significantly reduce internal fragmentation of the allocator. We evaluate the performance of our adapted allocator and compare it to a reference implementation of TLSF. Results show that the adapted allocator performs on par with the reference implementation for single allocations but is slightly slower for single frees and when applying allocation patterns from real-world programs. The findings of this work suggest that customizing allocators for garbage collection is worth considering and may be useful for future integration.

This thesis deals with the designing of a garbage collector for the PNtalk virtual machine. It describes and rates the approaches and algorithms for an automatic memory management. Four algorithm families ale presented: mark-sweep, mark-compact, copying algorithms and reference counting. At first it describes sequential forms, that pauses running of the main program (mutator), then it describes parallel and concurent forms, that do not pauses the mutator. The thesis also presents generational model of garbage collecting. The following sections briefly introduces object orientated Petri nets. The result of this thesis is the design of the generational garbage collector for the PNtalk virtual machine.

We present a distributed garbage collection algorithm for Java distributed objects using the object model provided by the Java Support for Distributed Objects (JSDA) object model and using weak references in Java. The algorithm can also be used for any other Java based distributed object models that use the stub-skeleton paradigm. Furthermore, the solution could also be applied to any language that supports weak references as a mean of interaction with the local garbage collector. We also give a formal definition and a proof of correctness for the proposed algorithm.

The design of a waste collection system affects public health, the extent of participation in the system by residents, the recovery of resources from waste, and the cost of collection. Many developing countries use communal container collection [CCC] systems in which large containers are dispersed throughout neighbourhoods for the storage of waste until collection. These systems tend to have limited success as they often do not garner viable amounts of participation and containers are prone to being overfilled. The communal container waste collection system in the city of Aguascalientes, AGS, Mexico was assessed according to the Integrated Solid Waste Management [ISWM] principles of social acceptability, environmental effectiveness, economic affordability and effective management. Information was collected through seven interviews with waste-related managers, 282 residential questionnaires, and 12 informal collector questionnaires. The collection system garners a high participation rate (99%) attributed to: non-burdensome one-way distances from residences to containers (mean 114+/-71m); thorough, daily collection; and a culture of cleanliness. Factors of adherence to waste collection regulations were found to be public knowledge, social acceptability, convenience and perception of importance. The collection system was assessed by rational-intuitive consideration of all indicators and principles, to be mostly acceptable from an ISWM framework due to: a high collection rate (~100% daily) which is enabled by effective monitoring and efficient operation; a high participation rate; similarity of the resource recovery rate to that of other developing and developed countries; and long-term affordability. Areas for improvement in equality of service provision, collaboration with informal collectors, and communication were identified. Lessons learned about communal container collection are applicable to lower-middle and upper-middle income countries.

Distributed stream-based applications manage large quantities of data and exhibit unique production and consumption patterns that set them apart from general-purpose applications. This dissertation examines possible ways of creating more efficient memory management schemes. Specifically, it looks at the memory reclamation problem. It takes advantage of special traits of streaming applications to extend the definition of the garbage collection problem for those applications and include not only data items that are not reachable but also items that have no effect on the final outcome of the application. Streaming applications typically fully process only a portion of the data, and resources directed towards the remaining data items (i.e., those that dont affect the final outcome) can be viewed as wasted resources that should be minimized. Two complementary approaches are suggested: 1. Garbage Identification 2. Adaptive Resource Utilization Garbage Identification is concerned with an analysis of dynamic data dependencies to infer those items that the application is no longer going to access. Several garbage identification algorithms are examined. Each one of the algorithms uses a set of application properties (possibly distinct from one another) to reduce the memory consumption of the application. The performance of these garbage identification algorithms is compared to the performance of an ideal garbage collector, using a novel logging/post-mortem analyzer. The results indicate that the algorithms that achieve a low memory footprint (close to that of an ideal garbage collector) perform their garbage identification decisions locally; however, they base these decisions on best-effort global information obtained from other components of the distributed application. The Adaptive Resource Utilization (ARU) algorithm analyzes the dynamic relationships between the production and consumption of data items. It uses this information to infer the capacity of the system to process data items and adjusts data generation accordingly. The ARU algorithm makes local capacity decisions based on best-effort global information. This algorithm is found to be as effective as the most successful garbage identification algorithm in reducing the memory footprint of stream-based applications, thus confirming the observation that using best-effort global information to perform local decisions is fundamental in reducing memory consumption for stream-based applications.

In the past years solid state disks have developed drastically and are now gaining increased popularity compared to conventional hard drives. While hard disk drives work predictable, transparent SSD routines work in the background without the user’s knowledge. This work describes the changes to the everyday life for forensic specialists; a forensic investigation includes data recovery and the gathering of a digital image of each acquired memory that provides proof of integrity through a checksum. Due to the internal routines, which cannot be stopped, checksums are falsified. Therefore the images cannot prove integrity of evidence anymore. The report proves the inconsistence of checksums of SSD and shows the differences in data recovery through high recovery rates on hard disk drives while SSD drives scored no recovery or very poor rates.

The design of a waste collection system affects public health, the extent of participation in the system by residents, the recovery of resources from waste, and the cost of collection. Many developing countries use communal container collection [CCC] systems in which large containers are dispersed throughout neighbourhoods for the storage of waste until collection. These systems tend to have limited success as they often do not garner viable amounts of participation and containers are prone to being overfilled. The communal container waste collection system in the city of Aguascalientes, AGS, Mexico was assessed according to the Integrated Solid Waste Management [ISWM] principles of social acceptability, environmental effectiveness, economic affordability and effective management. Information was collected through seven interviews with waste-related managers, 282 residential questionnaires, and 12 informal collector questionnaires. The collection system garners a high participation rate (99%) attributed to: non-burdensome one-way distances from residences to containers (mean 114+/-71m); thorough, daily collection; and a culture of cleanliness. Factors of adherence to waste collection regulations were found to be public knowledge, social acceptability, convenience and perception of importance. The collection system was assessed by rational-intuitive consideration of all indicators and principles, to be mostly acceptable from an ISWM framework due to: a high collection rate (~100% daily) which is enabled by effective monitoring and efficient operation; a high participation rate; similarity of the resource recovery rate to that of other developing and developed countries; and long-term affordability. Areas for improvement in equality of service provision, collaboration with informal collectors, and communication were identified. Lessons learned about communal container collection are applicable to lower-middle and upper-middle income countries.