Prestanda har historiskt sett alltid varit av betydelse för nyttjandet av datorer, vilket lett till att processorutvecklare har tagit fram flera olika metoder för att klämma ut mer processorkraft från processorn. Ett av dessa koncept är processorns cacheminne, som ansvarar för att lagra data processorn förväntar sig att behöva inom en snar framtid. Om cacheminnet nyttjats väl så innebär detta att processorn can behandla data i en mycket snabbare takt, vilket direkt påverkar prestanda. På grund av detta vill utvecklare gärna skriva kod som nyttjar cacheminnet till fullo. Detta är inte alltid en enkel uppgift, då de programmeringsmönster och beteenden utvecklaren måste anpassa sig till går att anse vara klumpiga för utvecklaren. Den här studioen kommer utforska möjligheterna att sammanfoga cachevänliga programmeringskoncept med utvecklarvänlig syntax, vilket resulterar i ett programmeringsspråk som är både läsbart, skrivbart samt effektivt med hänsyn till processorns cacheminne. För att lyckas med denna uppgift har studier på mönster inom minnesåtkomst, befintliga programmeringsspråk och kompilatordesign genomförts. Slutprodukten är ett språl vid namn Ghoul som implementerar cachevänliga koncept på en syntaktisk nivå, komplett med en fungerande kompilator. Utdata från denna kompilator blev senare prestandatestad för att avgöra huruvida de koncept språket introducerar har en märkbar påverkan på prestandan av program skrivna i detta språk. Testen visade att de tidigare nämnda konceptet direkt visar ett inflytande på hastigheten data kan behandlas i språket. / Performance has historically always been of importance to computing, and as such, processor developers have brought up several different methods to squeeze out more processing power from the processor. One of these concepts is the presence of a CPU cache memory, whose responsibility is to hold data the processor expects it might use soon. To utilize the cache well means that the processor can compute data at a much higher rate, resulting in a direct impact on performance. Therefore, it follows that it is in the developer’s best interest to write code capable of utilizing the cache memory to its full extent. This is not always an easy task however, as the patterns and style of programming the developer may need to adapt to can come of as cumbersome. This study will explore the possibilities of merging cache-friendly programming concepts with a developer-friendly syntax, resulting in a language that is both readable, writeable as well as efficient in regards to the processor cache. In order to accomplish this task, studies of memory access patterns, existing programming languages and compiler design has been performed. The end product is a language called Ghoul which successfully implements cache-friendly concepts on a syntactic level, complete with a working compiler. Outputs from this compiler were later benchmarked to assert that the concepts introduced had a measurable impact on the performance of programs written in Ghoul, showing that the aforementioned syntactical concepts indeed directly influence the speed at which data can be processed.

As Cloud services become more commonplace, recent works have uncovered vulnerabilities unique to such systems. Specifi cally, the paradigm promotes a risk of information leakage across virtual machine isolation via side-channels. Unlike conventional computing, the infrastructure supporting a Cloud environment allows mutually dis- trusting clients simultaneous access to the underlying hardware, a seldom met requirement for a side-channel attack. This thesis investigates the current state of side-channel vulnerabilities involving the CPU cache, and identifi es the shortcomings of traditional defenses in a Cloud environment. It explores why solutions to non-Cloud cache-based side-channels cease to work in Cloud environments, and describes new mitigation techniques applicable for Cloud security. Speci cally, it separates canonical cache-based side-channel attacks into two categories, Sequential and Parallel attacks, based on their implementation and devises a unique mitigation technique for each. Applying these solutions to a canonical Cloud environment, this thesis demonstrates the validity of these Cloud-specifi c, cache-based side-channel mitigation techniques. Furthermore, it shows that they can be implemented, together, as a server-side approach to improve security without inconveniencing the client. Finally, it conducts a comparison of our solutions to the current state-of-the-art. / Thesis (Master, Computing) -- Queen's University, 2013-09-25 18:03:47.737

Background. The frame rate of a game is important for both the end-user and the developer. Maintaining at least 60 FPS in a PC game is the current standard, and demands for efficient game applications rise. Currently, the industry standard within programming is to use Object-Oriented Design (OOD). But with the trend of larger sized games, this frame rate might not be maintainable using OOD. A design pattern that mitigates this is the Data-Oriented Design (DOD) which focuses on utilizing the CPU and memory efficiently. These design patterns differ in how they handle the data associated with them. Objectives. In this thesis, two games were created with two versions that used either OOD or DOD. The first game had multithreading included. New hardware utilizes several CPU cores, therefore, this thesis compares both singlethreaded and multithreaded versions of these design patterns.Methods. Experiments were made to measure the execution time and cache misses on the CPU. Each experiment started with a baseline that was gradually increased to stress the systems under test.Results. The results gathered from the experiments showed that the sections of the code that used DOD were significantly faster than OOD. DOD also had a better affinity with multithreading and was able to achieve at certain parts up to 13 times the speed of equivalent conditioned OOD. In the special case comparison DOD, even though it had larger objects, proved to be faster than OOD.Conclusions. DOD has shown to be significantly faster in execution time with fewer cache misses compared to OOD. Using multithreading for DOD presented to be the most efficient.

CPU cache hierarchies are the central solution in bridging the memory wall. A proper understanding of how to trade-off their high cost against performance can lead to cost-savings without sacrificing performance.Due to the combinatorial nature of the problem, there exist a large number of configurations to investigate, making design space exploration slow and cumbersome. To improve this process, this Thesis develops and evaluates a model for optimally trading-off cost and performance of CPU cache hierarchies, named the Optimal Cache Problem (OCP), in the form of a Non-linear Integer Problem. A second goal of this work is the development of an efficient solver for the OCP, which was found to be a branch & bound algorithm and proven to function correctly. Experiments were conducted to empirically analyse and validate the model and to showcase possible use-cases. There, it was possible to ascribe the model outputs on measurable performance metrics. The model succeeded in formalising the inherent trade-off between cost and performance in a way that allows for an efficient and complete search of the configuration space of possible cache hierarchies. In future work, the model needs to be refined and extended to allow for the simultaneous analysis of multiple programs.

Game engines process a lot of data under strict deadlines. Therefore, measures to increase performance are important in this area. Data-Oriented Design (DOD) promotes principles that are meant to increase performance by better cache utilization. The purpose of this thesis is to examine a selection of these principles to give a better understanding of how DOD affects CPU time and the rate of cache misses, with focus on the area of game development. More specifically, the principles examined are removal of run-time polymorphism, iteration over contiguous data, and lowering the amount of data in hot loops. Also, the Entity-Component-System pattern is examined, which is based upon DOD principles. The approach was to first present a theoretical background on the subject, and then to conduct tests by implementing a simulation of movement and collision detection utilizing said principles. The tests were written in C++ and executed on an Intel Core i7 4770k with no rendering. CPU time was measured in updated entities per μs, and cache utilization was measured in the form of cache miss rate. The results showed that the DOD principles did increase performance. Cache miss rate was also lower, with the exception of when removing run-time polymorphism. The conclusion is that Data-Oriented Design, used in game development, is likely to result in better performance, mostly as a result of better cache utilization.

Práce se zaměřuje na efektivní výpočet dvourozměrné diskrétní vlnkové transformace. Současné metody jsou v práci rozšířeny v několika směrech a to tak, aby spočetly tuto transformaci v jediném průchodu, a to případně víceúrovňově, použitím kompaktního jádra. Tohle jádro dále může být vhodně přeorganizováno za účelem minimalizace užití některých prostředků. Představený přístup krásně zapadá do běžně používaných rozšíření SIMD, využívá hierarchii cache pamětí moderních procesorů a je vhodný k paralelnímu výpočtu. Prezentovaný přístup je nakonec začleněn do kompresního řetězce formátu JPEG 2000, ve kterém se ukázal být zásadně rychlejší než široce používané implementace.