Garbage Collection Method Research Articles

Socio-ecological predictors of dengue in high incidence area of Delhi, India

Despite the amplified vector-control measures, sporadic-epidemic outbreaks of dengue incidence occurred in Delhi, intermittently. This study aimed to identify the major individual, household, and community level predictors of dengue cases in the hot-spots of Delhi. Primary survey data was collected from the selected sample of 347 households, at the South- West district of Delhi. This survey has interviewed the head of the household to collect the information of dengue incidences within last one year and household information related to socio-economic, demographic, environmental factors, such as housing pattern, density, water storage containers, drainage and garbage collection site and method, mosquito protection measures and awareness. Among 347 households, 54 households had reported dengue cases, and 69 individuals had reported dengue cases in last one year. Garbage and water collection site and methods, drainage and household type, household monthly income, indoor bamboo plants, construction site (within 500 m), presence of tertiary care hospital, were the significant predictors of dengue incidences in Delhi. In conclusion, strategic control measures and intense social interventions such as household and community awareness, promotion of healthy practices should be promoted to control the dengue incidences.

Path Optimisation of Electric Vehicles for Collection and Delivery based on Intelligent Waste Bins

This paper proposes a dynamic electric vehicle path optimization method for intelligent garbage collection and transportation systems to address the increasing uncertainty of urban household waste and the carbon emissions caused by vehicles in traditional garbage collection and transportation processes. With the goal of minimizing total cost and maximizing garbage collection and transportation, adjust the soft time window in a timely manner based on whether the amount of garbage generated by the intelligent garbage bin reaches the collection and transportation threshold. Taking into account the position of the garbage bin to be cleared, the position of the garbage collection and transportation vehicle, the amount of electricity, and the loading capacity, dynamically adjust the vehicle path. Due to the fact that genetic algorithms require a long time to converge to an acceptable solution, this paper uses greedy genetic algorithms to comprehensively utilize their advantages in local search and global search capabilities to achieve faster convergence solutions. The research results indicate that compared with traditional static garbage collection and transportation modes, dynamic garbage collection and transportation schemes can reduce total costs and increase garbage collection and transportation volume, and reasonable planning of the path of electric collection and transportation vehicles can effectively reduce carbon emissions. Finally, the effectiveness and efficiency of the algorithm were verified through comparative analysis of numerical examples.

Lifespan-based garbage collection to improve SSD's reliability and performance

Given the “out-of-place” nature of write mode, Solid State Drive (SSD) has to execute a garbage collection (GC) to reclaim the space of invalidated data and free flash blocks for new written data. However, the GC can incur the movements of valid data inside SSD, resulting in the problems such as write latency, write amplification, etc. The GC overheads of SSD depend not only on the current write pattern but also on how data have been already placed in SSD. If data can be classified by their lifetime when written to SSD, and the data with similar lifetime are written into the same flash block, we can select the block with the shortest expected lifespan as the victim block. Ideally, the victim block contains few valid data, implying there are few valid pages that need to be migrated during the GC process with greatly reduced overhead. In this paper, we propose and implement a GC method, called Lifespan-based GC, for SSDs based on the data lifetime, together with the I/O distribution and the dynamic flash memory allocation. The results show that for those applications with the data lifetime characteristics, the lifespan-based GC can effectively reduce the amount of valid pages migrated in GC process, thereby minimizing the write latency and write amplification caused by GC.

An analysis of concurrency control protocols for in-memory databases with CCBench

This paper presents yet another concurrency control analysis platform, CCBench. CCBench supports seven protocols (Silo, TicToc, MOCC, Cicada, SI, SI with latch-free SSN, 2PL) and seven versatile optimization methods and enables the configuration of seven workload parameters. We analyzed the protocols and optimization methods using various workload parameters and a thread count of 224. Previous studies focused on thread scalability and did not explore the space analyzed here. We classified the optimization methods on the basis of three performance factors: CPU cache, delay on conflict, and version lifetime. Analyses using CCBench and 224 threads, produced six insights. The performance of optimistic concurrency control protocol for a read-only workload rapidly degrades as cardinality increases even without L3 cache misses. (I2) Silo can outperform TicToc for some write-intensive workloads by using invisible reads optimization. (I3) The effectiveness of two approaches to coping with conflict (wait and no-wait) depends on the situation. (I4) OCC reads the same record two or more times if a concurrent transaction interruption occurs, which can improve performance. (I5) Mixing different implementations is inappropriate for deep analysis. (I6) Even a state-of-the-art garbage collection method cannot improve the performance of multi-version protocols if there is a single long transaction mixed into the workload. On the basis of I4, we defined the read phase extension optimization in which an artificial delay is added to the read phase. On the basis of I6, we defined the aggressive garbage collection optimization in which even visible versions are collected. The code for CCBench and all the data in this paper are available online at GitHub.

Влияние раздельного сбора отходов на эффективность «мусорной» реформы

The article considers the current problem for our country-separate collection of waste, the main source of which is the housing stock. It is shown that the absence of marked containers near residential buildings does not allow sorting garbage «at the source», which hinders the further rational use of resources. The author offers a classification of garbage collection methods used in the regions of our country, and highlights the most accessible of them. The article indicates that due to the lack of capacity and funds, small businesses can only be involved in certain stages of waste management that do not require expensive investments

Age Aware Pre-emptive Garbage Collection for SSD RAID

Flash-based storage systems offer high performance, robustness, and reliability for embedded applications; however the physical nature of flash memory means that there are limitations to its usage in high reliability applications. In previous work, we have developed RAID architectures and associated controller hardware that increase the reliability and lifespan of these storage systems. However, flash memory needs regular garbage collection and this presents two issues in a high reliability context. The first issue concerns response times as when a garbage collector is active, the flash memory cannot be used by the application layer. This non-determinism in terms of response is problematic in high reliability systems that require real-time guarantees. The second issue concerns lifespan of flash chips. If the garbage collector is allowed free rein over erase operations while garbage collecting, this affects management of the lifespan of each SSD in the array.In this paper we present an enhanced, dynamic, real-time garbage collection method for SSD RAID that does not ignore the strict age distribution management, while offering deterministic response times for access. Real-time efficiency is further improved by dynamically coordinating garbage collection across each device in the array. Our simulation results indicate that the dynamic garbage collection technique maintains the age distribution at a level that does not affect reliability of individual devices. This is evidences using various synthetic and realistic traces dominated by random I/O loads.

A fully concurrent garbage collector for functional programs on multicore processors

This paper presents a concurrent garbage collection method for functional programs running on a multicore processor. It is a concurrent extension of our bitmap-marking non-moving collector with Yuasa's snapshot-at-the-beginning strategy. Our collector is unobtrusive in the sense of the Doligez-Leroy-Gonthier collector; the collector does not stop any mutator thread nor does it force them to synchronize globally. The only critical sections between a mutator and the collector are the code to enqueue/dequeue a 32 kB allocation segment to/from a global segment list and the write barrier code to push an object pointer onto the collector's stack. Most of these data structures can be implemented in standard lock-free data structures. This achieves both efficient allocation and unobtrusive collection in a multicore system. The proposed method has been implemented in SML#, a full-scale Standard ML compiler supporting multiple native threads on multicore CPUs. Our benchmark tests show a drastically short pause time with reasonably low overhead compared to the sequential bitmap-marking collector.

플래시 메모리 기반 인덱스 구조에서 대리블록 이용한 가비지 컬렉션 기법

낸드 플래시 메모리는 빠른 접근 시간과 저전력의 특성을 가지고 있어 저장장치로 많이 사용되고 있는 추세이다. 하지만 저사양의 임베디드 장치에서는 메모리 요구사항과 구현상의 복잡성으로 FTL을 적용하기에는 비용이 많이 든다. 이러한 이유로 FTL을 구현하기 힘든 임베디드 장치에 적용할 수 있는 B+ 트리 연구들이 다수 제안되었다. 이런 연구들은 낸드 플래시 메모리에서 제자리 업데이트가 불가하다는 단점을 고려하여 삽입과 갱신의 성능을 최적화 하였다. 하지만 B+ 트리에 기존의 가비지 컬렉션 기법들을 적용하면 낸드 플래시 메모리의 페이지 위치를 변경하게 되고 B+ 트리의 재구성을 발생시켜 전체적인 성능을 저하시킨다. 이러한 문제를 해결하고자 본 논문에서는 낸드 플래시 메모리를 기반으로 하는 B+ 트리와 이와 유사한 인덱스 트리 구조에 적용할 수 있는 가비지 컬렉션 기법을 제안한다. 제안하는 가비지 컬렉션 기법은 블록 정보 테이블과 대리 블록을 이용하여 B+ 트리의 재구성을 발생시키지 않는다. 제안된 기법의 성능평가를 위해, 낸드 플래시 메모리가 장착된 실험 장치에 B+ 트리와 <TEX>${\mu}$</TEX>-Tree를 구현하고 제안된 기법을 적용하였다. 구현 결과 B+ 트리에서 제안된 기법이 GAGC(Greedy Algorithm Garbage Collection)보다 삽입된 키의 개수가 약 73% 많았으며, <TEX>${\mu}$</TEX>-Tree에서 제안된 기법이 GAGC보다 시간 오버헤드가 약39% 적었다. Recently, NAND flash memories are used for storage devices because of fast access speed and low-power. However, applications of FTL on low power computing devices lead to heavy workloads which result in a memory requirement and an implementation overhead. Consequently, studies of B+-Tree on embedded devices without the FTL have been proposed. The studies of B+-Tree are optimized for performance of inserting and updating records, considering to disadvantages of the NAND flash memory that it can not support in-place update. However, if a general garbage collection method is applied to the previous studies of B+-Tree, a performance of the B+-Tree is reduced, because it generates a rearrangement of the B+-Tree by changing of page positions on the NAND flash memory. Therefor, we propose a novel garbage collection method which can apply to the B+-Tree based on the NAND flash memory without the FTL. The proposed garbage collection method does not generate a rearrangement of the B+-Tree by using a block information table and a proxy block. We implemented the B+-Tree and <TEX>${\mu}$</TEX>-Tree with the proposed garbage collection on physical devices with the NAND flash memory. In experiment results, the proposed garbage collection scheme compared to greedy algorithm garbage collection scheme increased the number of inserted keys by up to about 73% on B+-Tree and decreased elapsed time of garbage collection by up to about 39% on <TEX>${\mu}$</TEX>-Tree.

BLF: an efficient flash translation layer scheme for flash-based storage systems

The performance of flash memory is limited by its “erase-before-write,” and erase operations can only be performed in a much larger unit than write operations. To address these problems, we propose an efficient flash translation layer scheme called BLF: Block List Flash Translation Layer. BLF unites log blocks and physical blocks for servicing update requests. It can avoid uneven erasing and low block utilization. The address translation table of BLF can avoid storing an extra internal mapping table. BLF’s garbage collection method divides the storage zone into three levels: the active zone where hot data are stored, the inactive zone where cold data are stored, and the transitional zone where reclamation block is stored. If invalid blocks can be reclaimed properly and intensively, merging log blocks with physical blocks can be avoided and the amount of operations can be reduced. Finally, we implement an accurate flash simulator to evaluate the efficacy of BLF and compare it with other flash schemes, demonstrating that the improved performance resulting from BLF substantially outperforms other flash schemes.

Study on Ecological Footprint Calculation of Beijing's Urban Domestic Garbage

This article was based on Beijing urban garbage collection and disposal methods, namely, vehicle transport, landfill, composting and incineration, etc. According to garbage collection and processing methods and combining with the 2006 IPCC internationally cognition and greenhouse gas calculation that related scholars studied, ecological footprint calculation of Beijing's urban domestic garbage was summarized and developed, thus laid foundation for the study of Beijing urban ecological carrying capacity.

Memory Compaction Scheme with Block-Level Buffer for Large Flash Memory

In flash memory, many previous garbage collection methods only merge blocks statically and do not consider the contents of buffer. These schemes may cause more unnecessary block erase operations and page copy operations. However, since flash memory has the limitation of maximum rate and life cycle to delete each block, an efficient garbage collection method to evenly wear out the flash memory region is needed. This paper proposes a memory compaction scheme based on block-level buffer for flash memory. The proposed scheme not only merges the data blocks and the corresponding log block, but also searches for the block-level buffer to find the corresponding buffer blocks. Consequently, unnecessary potential page copying operations and block erasure operations could be reduced, thereby improving the performance of flash memory and prolonging the lifetime of flash memory.

An efficient multimedia file system for NAND flash memory storage

Since the existing NAND flash memory file systems manage file data in page units, the memory usage increases greatly as the number and size of files increase, and the area to scan at the mounting time increases linearly as well. To resolve these problems, this paper suggests data management in segment units for more efficient processing of multimedia files to reduce memory usage and to improve reading and writing performance. In addition, it suggests a new index structure and garbage collection method for multimedia files to reduce the mounting time and to improve the wear-leveling effectiveness. This approach shows better performance for multimedia files than existing file systems in terms of reading, writing, memory usage, mounting time, and garbage collection.

A novel processor architecture with exact tag-free pointers

Along with the success of Java, garbage collection advances to embedded and real-time systems. In this paper a novel RISC processor architecture that lays the foundation for efficient real-time garbage collection in hardware and guarantees pointer integrity at the machine-code level is proposed. This article summarizes the most commonly used garbage collection methods and points out problems of contemporary software-based solutions to motivate architectural support for garbage collection.

Autonomous garbage collection: resolving memory leaks in long-running server applications

We demonstrate the benefits of a garbage collection technique that requires neither programmer assistance nor rebuilding (compiling or linking) of target applications. That is, our approach effectively mitigates performance degeneration due to memory leaks in applications when the source and object code are unavailable. Our technique is an extension of the garbage collection method known as conservative garbage collection. We refer to our approach as autonomous garbage collection. Autonomous garbage collection is especially useful for long running server applications in large-scale information processing server environments. Our prototype demonstrates that this garbage collection technique is feasible. Our experimental results show that this technique is more general and easier to use than many of the previous garbage collection proposals targeted at resolving memory leaks in non-cooperative server applications.

Health hazards to the small ruminant population of the Middle East posed by the trade of sheep and goat meat.

Meat consumers in the Middle East traditionally prefer meat from freshly slaughtered animals to that from chilled or frozen carcasses. Consequently, meat trade in the Middle East is based mainly upon the importation of large quantities of live animals rather than of sheep and goat carcasses. Furthermore, as it seems that pathogens remain viable for longer periods of time in live animals than in meat, the probability of pathogens spreading in the Middle East as a result of contaminated small ruminant carcasses is lower than the probability of pathogens being imported through live animals. With suitable environmental conditions, however, there are two livestock diseases which may spread through meat, namely: foot and mouth disease (FMD) and transmissible spongiform encephalopathies (TSEs). Foot and mouth disease virus which might have survived in the bones and offal of animals slaughtered in FMD-infected areas may be transmitted to animals in other regions. This occurs if carcass waste matter is not properly disposed of and is a particular problem where scavenging animals may carry away the infective material. Due to the low standards in garbage and sewage collection methods in many regions of the Middle East, such an eventuality should never be overlooked. Transmissible spongiform encephalopathies may be introduced into sensitive animal populations if the waste matter of slaughtered sheep and goats is processed into animal feed. This would occur if animal products which have not undergone treatment to inactivate the scrapie agent are used in the rendering process. The risk of introducing TSEs into livestock populations of the Middle East in this way is very low, since the rendering technology and the use of animal waste matter as feed are not part of the local traditional husbandry practices.