Purely functional languages--with static type systems and dynamic memory management using garbage collection--are a known tool for helping programmers to reduce the number of memory errors in programs. By using such languages, we can establish correctness properties relating to memory-safety through our choice of implementation language alone. Unfortunately, the language characteristics that make purely functional languages safe also make them more difficult to apply in a low-level domain like operating systems construction. The low-level features that support the kinds of hardware manipulations required by operating systems are not typically available in memory-safe languages with garbage collection. Those that are provided may have the ability to violate memory- and type-safety, destroying the guarantees that motivate using such languages in the first place. This work demonstrates that it is possible to bridge the gap between the requirements of operating system implementations and the features of purely functional languages without sacrificing type- and memory-safety. In particular, we show that this can be achieved by isolating the potentially unsafe memory operations required by operating systems in an abstraction layer that is well integrated with a purely functional language. The salient features of this abstraction layer are that the operations it exposes are memory-safe and yet sufficiently expressive to support the implementation of realistic operating systems. The abstraction layer enables systems programmers to perform all of the low-level tasks necessary in an OS implementation, such as manipulating an MMU and executing user-level programs, without compromising the static memory-safety guarantees of programming in a purely functional language. A specific contribution of this work is an analysis of memory-safety for the abstraction layer by formalizing a meaning for memory-safety in the presence of virtual-memory using a novel application of noninterference security policies. In addition, we evaluate the expressiveness of the abstraction layer by implementing the L4 microkernel API, which has a flexible set of virtual memory management operations.

The aim of this master's thesis is to design and implement JavaScript interpreter which is designed for purposes of avoiding obfuscation code of various types of computer viruses. This master's thesis also comprises a detailed view into the inner mechanism of the ECMAScript standard.

Indiana University-Purdue University Indianapolis (IUPUI) / Between 1890 and 1930 in the city of Indianapolis, people in charge made certain decisions regarding infrastructure—the character and condition of streets and sidewalks, the provision of sewer services and garbage collection, the location of the city’s dump, and the placement of the city’s sewage treatment plant—that resulted in long-term health and safety consequences. In Indianapolis, as in most modern American cities, some neighborhoods are less healthy for their inhabitants than others. The least healthy neighborhoods—those with the highest rates of cancer, for example—are situated on the city’s southwest side. The southwest side of Indianapolis is also the location of the landfill, the sewage treatment plant, and much heavy industry. The entire city is at the mercy of an ill-designed sewer system, a system that taxpayers are spending millions annually to repair. The years from 1890 to 1930 saw the genesis of this state of affairs. In the city of Indianapolis since 1890, infrastructure has separated people from nature and from each other on two levels: its operational level, wherein it was an objective entity that performed according to its design, and its subjective level, where it operated as a social and hygienic barrier. Streets, curbs, sewers, and sidewalks are useful and necessary elements of public health and safety. We both want and need these elements to ensure our separation from things that are dangerous, such as speeding cars and contaminated water. When government officials exercise power to declare what parts of the city street are accessible to whom, or which neighborhoods will have a wastewater treatment plant, a landfill, or heavy industry nearby, infrastructure can work to separate people.

Denna rapport jämför prestanda med Unitys nya inkrementella garbage collection system med deras tidigare stop the world system, samt analyserar effekten av objektpooling på tidsprestanda. De olika systemen testas med hjälp av en förenklad version av ett bullet hell spel, där flertalet kulor skapas och förstörs per sekund. Rapporten finner att användning av objektpooling drastiskt förbättrar prestanda i den givna testmiljön. Rapporten finner även att stop the world presterar något bättre i genomsnitt, men dess extremvärden är markant högre på grund av garbage collection spikar. Rapporten rekommenderar användning av pooling samt användning av det inkrementella garbage collection systemet för att minimera överskridande av spelets tidsbudget per bilduppdatering.

<p> This study determines the potential for expansion within Third Sector Employment Enterprises: the recycling operation in Hamilton-Wentworth. Although the company has been in existence since 1977, it has not yet reached the level of viability achieved by other firms established at that time . This study involves a comparison of Third Sector with Halton,s Recycled Resources: the recycling firm in the Region of Halton. The comparison attempts to determine what factors within Third Sector and Hamilton-Wentworth are retarding the growth of the company. A quantitative comparison was used to contrast the net revenues of the two companies, and descriptive data was used to explain and qualify the quantitative findings. The analysis reveals that despite the operational differences between the two companies, it is community participation that makes Halton's Recycled Resources more viable than Third Sector. The concluding remarks make some suggestions as to how community participation, and thus Third Sector's operation can be improved. </p> / Thesis / Bachelor of Arts (BA)

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Java is one of the more recent programming languages that in runtime free applications from manual memory management by using automatic Garbage collector (GC) threads. Although, at the cost of stop-the-world pauses that pauses the whole application. Since the initial GC algorithms new collectors has been developed to improve the performance of Java applications. Still, memory related errors occurs and developers struggle to pick the correct GC for each specific case. Since the concept of microservices were established the benefits of using it over a monolith system has been brought to attention but there are still problems to solve, some associated to garbage collectors. In this study the performance of garbage collectors are evaluated and compared in a microservice environment. The measurements were conducted in a Java SpringBoot application using Docker and a docker compose file to simulate a microservice environment. The application outputted log files that were parsed into reports which were used as a basis for the analysis. The tests were conducted both with and without a database connection. Final evaluations show that one GC does not fit all application environments. ZGC and Shenandoah GC was proven to perform very good regarding lowering latency, although not being able to handle the a microservice environment as good as CMS. ZGC were not able to handle the database connection tests at all while CMS performed unexpectedly well. Finally, the study enlightens the importance of balancing between memory and hardware usage when choosing what GC to use for each specific case.

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.