Flash-based Solid State Drives Research Articles

A High-Performance and Scalable NVMe Controller Featuring Hardware Acceleration

Nonvolatile memory express (NVMe) is a high-performance and scalable PCI express (PCIe)-based interface for the host software communicating with NVMs, including NAND Flash and the storage class memories (SCMs). NVMe solid-state drives (SSDs) have been deployed in cloud platforms and data-centers for a variety of I/O intensive applications due to their performance benefits compared to SATA/SAS SSDs. Considering the design flexibility, firmware-based NVMe controllers are typically used in Flash-based NVMe SSDs but may occupy a significant portion of processor resources and power consumption to achieve high performance. Moreover, the firmware component can be a critical performance bottleneck for SCMs that are an order-of-magnitude faster than Flash. To address these challenges, hardware-accelerated NVMe controllers have emerged in both industry and academia. The commercial hardware controllers are confidential, whereas current academic studies still spare much room for architecture innovations. In this article, we propose an opensource ultralow-latency and high-throughput NVMe controller with a highly parallel, pipelined, and scalable architecture that accommodates one admin controller and multiple fully hardware-automated I/O controllers. We perform extensive empirical performance evaluations concerning the NVMe I/O size, queue depth, queue number, read-to-write ratio, and access pattern. The maximum read/write bandwidth can achieve 7.0 GB/s, accounting for 89&#x0025; of the PCIe bandwidth. The 4-KB-sized read/write throughput can attain 1.7 million I/O operations per second (MIOPS), whereas the average latency is merely 2.4 <inline-formula> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula>/3.2 <inline-formula> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula>. Compared to state-of-the-art NVMe controllers in academia, the 4-KB-sized read/write bandwidth of our controller reaches <inline-formula> <tex-math notation="LaTeX">$2.2 \times /2.3\times $ </tex-math></inline-formula> as high and the latency is <inline-formula> <tex-math notation="LaTeX">$5.1 \times /4.9\times $ </tex-math></inline-formula> lower.

Design and Implementation of Virtual Stream Management for NAND Flash-Based Storage

NAND flash memory is being widely used as data storage in consumer electronics devices such as tablet computers and smartphones. However, due to the inherent nature of NAND flash memory where in-place update is not supported, NAND flash-based SSDs (Solid-State Drives) suffer from severe performance degradation as they need to move valid data during garbage collection (GC). Recently, multi-streamed SSDs have been proposed to reduce the cost of GC in the SSDs. However, commercial SSDs used in consumer electronics devices support only a small number of streams due to the device’s limitation in hardware resources. This makes it difficult to fully utilize the benefits of the multi-streamed SSDs. In this article, we propose a new concept of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">virtual streams</i> ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">vStreams</i> ) that are independent of the number of available streams within the multi-streamed SSDs. We present the design and implementation of virtual stream management architecture, called vStream-FTL, for efficient stream management in the SSD. Specifically, we present novel mechanisms to monitor the lifetime of each stream with a negligible memory overhead and map one or more vStreams into a physical stream at run time according to the lifetime of vStream. In addition, we implement the enhanced garbage collection scheme, called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">vStream-aware GC</i> that increases the benefits of multi-streamed SSDs further. Our vStream-FTL allows embedded system developers to manage a sufficient number of streams regardless of the physical streams supported by the device. The evaluation results with smartphone workload show that the proposed vStream-FTL improves throughput by 48% compared to the Legacy-FTL with no stream support.

Garbage Collection Algorithms in Flash Based Solid State Drives

Solid state drives (SSDs)have emerged as faster and more reliable data storages over the last few years. Their intrinsic characteristics prove them to be more efficient as compared to other traditional storage media such as the Hard Disk Drives (HDDs). Issues such as write amplification, however, degrade the performance and lifespan of an SSD. This issue is in turn handled by the Garbage Collection (GC) algorithms that are put in place to supply free blocks for serving the writes being made to the flash-based SSDs and thus reduce the need of extra unnecessary writes. The LRU/FIFO, Greedy, Windowed Greedy and D choices algorithms have been described to lower write amplification for incoming writes which are different in nature. The performance of the GC algorithms varies based on factors such as pre-defined hot/cold data separation, hotness of data, uniform/non-uniform nature of incoming writes, the GC window size and the number of pages in each block of the flash memory package. Finally, it can be seen that the number of write frontiers so used, can dictate the separation of hot/cold data and increase the performance of a GC algorithm.

Improving I/O performance in distributed file systems for flash-based SSDs by access pattern reshaping

Cloud computing is being widely adopted in the industry due to improve resource utilization and provide more computation power. In cloud computing systems, many numbers of users execute various types of applications that produce a large amount of data. To store large data, distributed file systems are used in many cloud computing systems. Recently, to improve the performance of distributed file systems, emerging flash-based solid-state drives (SSDs) are widely adopted since they provide high performance compared with existing hard disk drives (HDDs). However, due to the characteristics of SSDs, the performance of distributed file systems is greatly impacted by the access patterns from the applications. For example, the performance of random writes in SSDs is lower than that of sequential writes. In this article, we propose an address reshaping technique for SSDs in distributed file systems to improve the performance of random writes by transforming the access patterns. Our scheme reshapes random write requests into sequential write requests in the distributed file systems. This enables the distributed file systems to issue the sequential write requests to SSDs. The experimental results show that the proposed scheme improves performance by up to 46.26% compared with the existing scheme.

Design and Implementation of SSD-Assisted Backup and Recovery for Database Systems

As flash-based solid-state drive (SSD) becomes more prevalent because of the rapid fall in price and the significant increase in capacity, customers expect better data services than traditional disk-based systems. However, the order of magnitude performance provided and new characteristics of flash require a rethinking of data services. For example, backup and recovery is an important service in a database system since it protects data against unexpected hardware and software failures. To provide backup and recovery, backup/recovery tools or backup/recovery methods by operating systems can be used. However, the tools perform time-consuming jobs, and the methods may negatively affect run-time performance during normal operation even though high-performance SSDs are used. To handle these issues, we propose an SSD-assisted backup/recovery scheme for database systems. Our scheme is to utilize the characteristics (e.g., out-of-place update) of flash-based SSD for backup/recovery operations. To this end, we exploit the resources (e.g., flash translation layer and DRAM cache with supercapacitors) inside SSD, and we call our SSD with new backup/recovery functionality BR-SSD. We design and implement the functionality in the Samsung enterprise-class SSD (i.e., SM843Tn) for more realistic systems. Furthermore, we exploit and integrate BR-SSDs into database systems (i.e., MySQL) in replication and redundant array of independent disks (RAID) environments, as well as a database system in a single BR-SSD. The experimental result demonstrates that our scheme provides fast backup and recovery but does not negatively affect the run-time performance during normal operation.

A Preliminary Study: Towards Parallel Garbage Collection for NAND Flash-Based SSDs

NAND Flash-based solid-state drives (SSDs) have been widely used as secondary storage devices due to their faster access speed, lower power consumption, and higher reliability compared with hard disk drives. However, application I/O performance can be significantly affected by garbage collection (GC) inside SSDs. For example, a GC operation usually moves valid pages from a victim block into a clean block in a serialized manner. Thus, it increases the GC time and affects the application I/O performance. To address this issue, this article presents a preliminary study on a parallel GC scheme for flash-based SSDs. In our scheme, we parallelize valid page migrations during a GC operation to reduce the total GC time. To do this, we first propose a new flash chip architecture that enables valid page migrations in parallel. Second, we collect information such as new addresses for the migration of valid pages by considering the restriction of SSD operations. Finally, we employ multiple worker threads to migrate the valid pages using the collected information in a parallel manner. We implement and evaluate our scheme using Disksim with Microsoft SSD extension. The experimental result shows that the proposed scheme reduces the overall GC time by 70% and 57% on average compared with the existing scheme and a state-of-the-art GC scheme IPPBE, respectively.

Extending SSD Lifespan with Comprehensive Non-Volatile Memory-Based Write Buffers

New non-volatile memory (NVM) technologies are expected to replace main memory DRAM (dynamic random access memory) in the near future. NAND flash technological breakthroughs have enabled wide adoption of solid state drives (SSDs) in storage systems. However, flash-based SSDs, by nature, cannot avoid low endurance problems because each cell only allows a limited number of erasures. This can give rise to critical SSD reliability issues. Since many SSD write operations eventually cause many SSD erase operations, reducing SSD write traffic plays a crucial role in SSD reliability. This paper proposes two NVM-based buffer cache policies which can work together in different layers to maximally reduce SSD write traffic: a main memory buffer cache design named Hierarchical Adaptive Replacement Cache (H-ARC) and an internal SSD write buffer design named Write Traffic Reduction Buffer (WRB). H-ARC considers four factors (dirty, clean, recency, and frequency) to reduce write traffic and improve cache hit ratios in the host. WRB reduces block erasures and write traffic further inside an SSD by effectively exploiting temporal and spatial localities. These two comprehensive schemes significantly reduce total SSD write traffic at each different layer (i.e., host and SSD) by up to 3x. Consequently, they help extend SSD lifespan without system performance degradation.

Probabilistic Page Replacement Policy in Buffer Cache Management for Flash-Based Cloud Databases

In the fast evolution of storage systems, the newly emerged flash memory-based Solid State Drives (SSDs) are becoming an important part of the computer storage hierarchy. Amongst the several advantages of flash-based SSDs, high read performance, and low power consumption are of primary importance. Amongst its few disadvantages, its asymmetric I/O latencies for read, write and erase operations are the most crucial for overall performance. In this paper, we proposed two novel probabilistic adaptive algorithms that compute the future probability of reference based on recency, frequency, and periodicity of past page references. The page replacement is performed by considering the probability of reference of cached pages as well as asymmetric read-write-erase properties of flash devices. The experimental results show that our proposed method is successful in minimizing the performance overheads of flash-based systems as well as in maintaining the good hit ratio. The results also justify the utility of a genetic algorithm in maximizing the overall performance gains.

Modeling the Endurance Reliability of Intradisk RAID Solutions for Mid-1X TLC NAND Flash Solid-State Drives

Ensuring data protection in solid state drives (SSDs) is vital in enterprise application scenario. However, as the reliability of their storage medium, namely, the NAND Flash, is decreasing at the same pace of the technology scaling, this activity is becoming nontrivial. The evaluation of different recovery strategies that employ complex error-correction codes and second-level error correction is becoming a de facto . In this paper, we model the endurance reliability of an advanced data protection methodology like the intradisk redundant array of independent disks (RAIDs) applied on mid-1X triple level cell NAND Flash-based SSD. The performed investigations include a parametric analysis of the uncorrectable bit-error rate. By developing a dedicated discrete-time Markov-chain model of an SSD, we evidenced that intradisk RAID5 and RAID6 allow achieving an inherent reliability level compliant with the qualification target for enterprise SSD. Finally, we provide a global picture of the disk economy when intradisk RAID is implemented.

Solid-State Drives (SSDs) [Scanning the Issue

The articles in this special issue cover all the most recent advances in the solid-state drive field from both hardware and software/firmware perspectives. If we look at the DRAM history, DRAM data access speeds have increased at a faster rate than HDDs. The gap in read and write performances between DRAM and HDD has widened in the last years, leaving an opportunity for a new intermediate memory/storage technology between HDDs and DRAM: nand Flash-based SSDs can fill this performance gap, thus profoundly changing the traditional memory hierarchy below the microprocessor.

LDM

With the explosive growth in data volume, the I/O bottleneck has become an increasingly daunting challenge for big data analytics. Economic forces, driven by the desire to introduce flash-based Solid-State Drives (SSDs) into the high-end storage market, have resulted in hybrid storage systems in the cloud. However, a single flash-based SSD cannot satisfy the performance, reliability, and capacity requirements of enterprise or HPC storage systems in the cloud. While an array of SSDs organized in a RAID structure, such as RAID5, provides the potential for high storage capacity and bandwidth, reliability and performance problems will likely result from the parity update operations. In this article, we propose a Log Disk Mirroring scheme (LDM) to improve the performance and reliability of SSD-based disk arrays. LDM is a hybrid disk array architecture that consists of several SSDs and two hard disk drives (HDDs). In an LDM array, the two HDDs are mirrored as a write buffer that temporally absorbs the small write requests. The small and random write data are written on the mirroring buffer by using the logging technique that sequentially appends new data. The small write data are merged and destaged to the SSD-based disk array during the system idle periods. Our prototype implementation of the LDM array and the performance evaluations show that the LDM array significantly outperforms the pure SSD-based disk arrays by a factor of 20.4 on average, and outperforms HPDA by a factor of 5.0 on average. The reliability analysis shows that the MTTDL of the LDM array is 2.7 times and 1.7 times better than that of pure SSD-based disk arrays and HPDA disk arrays.

Exploiting Sequential and Temporal Localities to Improve Performance of NAND Flash-Based SSDs

NAND flash-based Solid-State Drives (SSDs) are becoming a viable alternative as a secondary storage solution for many computing systems. Since the physical characteristics of NAND flash memory are different from conventional Hard-Disk Drives (HDDs), flash-based SSDs usually employ an intermediate software layer, called a Flash Translation Layer (FTL). The FTL runs several firmware algorithms for logical-to-physical mapping, I/O interleaving, garbage collection, wear-leveling, and so on. These FTL algorithms not only have a great effect on storage performance and lifetime, but also determine hardware cost and data integrity. In general, a hybrid FTL scheme has been widely used in mobile devices because it exhibits high performance and high data integrity at a low hardware cost. Recently, a demand-based FTL based on page-level mapping has been rapidly adopted in high-performance SSDs. The demand-based FTL more effectively exploits the device-level parallelism than the hybrid FTL and requires a small amount of memory by keeping only popular mapping entries in DRAM. Because of this caching mechanism, however, the demand-based FTL is not robust enough for power failures and requires extra reads to fetch missing mapping entries from NAND flash. In this article, we propose a new flash translation layer called LAST++. The proposed LAST++ scheme is based on the hybrid FTL, thus it has the inherent benefits of the hybrid FTL, including low resource requirements, strong robustness for power failures, and high read performance. By effectively exploiting the locality of I/O references, LAST++ increases device-level parallelism and reduces garbage collection overheads. This leads to a great improvement of I/O performance and makes it possible to overcome the limitations of the hybrid FTL. Our experimental results show that LAST++ outperforms the demand-based FTL by 27% for writes and 7% for reads, on average, while offering higher robustness against sudden power failures. LAST++ also improves write performance by 39%, on average, over the existing hybrid FTL.

Supporting System Consistency with Differential Transactions in Flash-Based SSDs

Embedded transaction design inside solid state drives (SSDs) is an attractive way to support system consistency with low overhead due to the no-overwrite property of flash memory. Recent research proposes shadow paging variants to reduce write traffic to SSDs for longer lifetime while leveraging the random performance of SSDs. However, writes in transactions usually are small, and the page-aligned shadow paging protocols still incur high write amplification, which hurts SSD lifetime. In this paper, we propose an embedded transaction protocol, DiffTx, which differentially logs partial page updates in a write-ahead logging way and writes full page updates in a shadow paging way, aiming at low write amplification. DiffTx further improves transaction performance using two techniques. First, by clustering mapping metadata of full page updates with differential data of partial page updates in a single record, DiffTx tracks pages of each transaction at low overhead. Second, DiffTx removes the write ordering on commit by delaying the completeness check of writes, leveraging the clean-state write property of flash memory. Experiments show that DiffTx improves throughput by 25.9 percent and halves write traffic on average compared to TxFlash, a typical embedded transaction protocol for flash memory.

High-Performance and Lightweight Transaction Support in Flash-Based SSDs

Flash memory has accelerated the architectural evolution of storage systems with its unique characteristics compared to magnetic disks. The no-overwrite property of flash memory naturally supports transactions, a commonly used mechanism in systems to provide consistency. However, existing embedded transaction designs in flash-based Solid State Drives (SSDs) either limit the transaction concurrency or introduce high overhead in tracking transaction states. This leads to low or unstable SSD performance. In this paper, we propose a transactional SSD (TxSSD) architecture, LightTx, to enable better concurrency and low overhead. First, LightTx improves transaction concurrency arbitrarily by using a page-independent commit protocol. Second, LightTx tracks the recent updates by leveraging the near-log-structured update property of SSDs and periodically retires dead transactions to reduce the transaction state tracking cost. Experiments show that LightTx achieves nearly the lowest overhead in garbage collection, memory consumption and mapping persistence compared to existing embedded transaction designs. LightTx also provides up to 20.6 percent performance improvement due to improved transaction concurrency.

SSD 수명 관점에서 리눅스 I/O 스택에 대한 실험적 분석

낸드 플래시 기반의 SSD (Solid-State Drive)는 HDD (Hard Disk Drive) 대비 월등한 성능에도 불구하고 쓰기 회수 제한이라는 태생적 단점을 가지고 있다. 이로 인해 SSD의 수명은 워크로드에 의해 결정되어 SSD의 기술 변화 추세인 SLC (Single Level Cell) 에서 MLC (Multi Level Cell) 로의 전환, MLC에서 TLC (Triple Level Cell) 로의 전환에 있어 큰 도전이 될 수 있다. 기존 연구들은 주로 wear-leveling 또는 하드웨어 아키텍처 측면에서 SSD의 수명 개선을 다루었으나, 본 논문에서는 호스트가 요청한 쓰기에 대해 SSD가 낸드플래시 메모리를 통해 처리하는 수명관점의 효율성을 대변하는 WAF (Write Amplification Factor) 관점에서 Host I/O 스택 중 파일 시스템, I/O 스케줄러, 링크 전력에 대해 JEDEC 엔터프라이즈 워크로드를 이용해 I/O 스택 최적 구성에 대해 실험적 분석을 수행하였다. WAF는 SSD의 FTL의 효율성을 측정하는 지표로 수명관점에서 가장 객관적으로 사용한다. I/O 스택에 대한 수명 관점의 최적 구성은 MinPower-Dead-XFS로 최대 성능 조합인 MaxPower-Cfq-Ext4에 비해 성능은 13% 감소하였지만 수명은 2.6 배 연장됨을 확인하였다. 이는 I/O 스택의 최적화 구성에 있어, SSD 성능 관점뿐만 아니라 수명 관점의 고려에 대한 유의미를 입증한다.

H-Hash: A Hash Index Structure for Flash-Based Solid State Drives

Flash-based solid state drives (SSDs) have been widely used as storage medium because of their fast access speed, high reliability and low power consumption. In spite of these advantages, they inherit distinct characteristics such as no in-place updates, asymmetric operation speed and unit because they consist of NAND flash memories. Therefore, a disk-based hash index structure may result in severe performance degradation if it is directly deployed on a NAND flash memory-based storage system. In this paper, we propose a new hybrid hash index structure for flash-based SSDs. It delays and reduces the split operations which cause slow block erasure and additional read and write operations by exploiting overflow buckets according to the ratio of updates and deletions. Through various performance evaluations, we show the superiority of our proposed index structure by comparing it to other hash index structures for flash-based SSDs.

A Large-Scale Study of Flash Memory Failures in the Field

Servers use flash memory based solid state drives (SSDs) as a high-performance alternative to hard disk drives to store persistent data. Unfortunately, recent increases in flash density have also brought about decreases in chip-level reliability. In a data center environment, flash-based SSD failures can lead to downtime and, in the worst case, data loss. As a result, it is important to understand flash memory reliability characteristics over flash lifetime in a realistic production data center environment running modern applications and system software. This paper presents the first large-scale study of flash-based SSD reliability in the field. We analyze data collected across a majority of flash-based solid state drives at Facebook data centers over nearly four years and many millions of operational hours in order to understand failure properties and trends of flash-based SSDs. Our study considers a variety of SSD characteristics, including: the amount of data written to and read from flash chips; how data is mapped within the SSD address space; the amount of data copied, erased, and discarded by the flash controller; and flash board temperature and bus power. Based on our field analysis of how flash memory errors manifest when running modern workloads on modern SSDs, this paper is the first to make several major observations: (1) SSD failure rates do not increase monotonically with flash chip wear; instead they go through several distinct periods corresponding to how failures emerge and are subsequently detected, (2) the effects of read disturbance errors are not prevalent in the field, (3) sparse logical data layout across an SSD's physical address space (e.g., non-contiguous data), as measured by the amount of metadata required to track logical address translations stored in an SSD-internal DRAM buffer, can greatly affect SSD failure rate, (4) higher temperatures lead to higher failure rates, but techniques that throttle SSD operation appear to greatly reduce the negative reliability impact of higher temperatures, and (5) data written by the operating system to flash-based SSDs does not always accurately indicate the amount of wear induced on flash cells due to optimizations in the SSD controller and buffering employed in the system software. We hope that the findings of this first large-scale flash memory reliability study can inspire others to develop other publicly-available analyses and novel flash reliability solutions.

Effective flash-based SSD caching for high performance home cloud server

In the home cloud environment, the storage performance of home cloud servers, which govern connected devices and provide resources with virtualization features, is critical to improve the end-user experience. To improve the storage performance of virtualized home cloud servers in a cost-effective manner, caching schemes using flash-based solid state drives (SSD) have been widely studied. Although previous studies successfully narrow the speed gap between memory and hard disk drives, they only focused on how to manage the cache space, but were less interested in how to use the cache space efficiently taking into account the characteristics of flash-based SSD. Moreover, SSD caching is used as a read-only cache due to two well-known limitations of SSD: slow write and limited lifespan. Since storage access in virtual machines is performed in a more complex and costly manner, the limitations of SSD affect more significantly the storage performance. This paper proposes a novel SSD caching scheme and virtual disk image format, named sequential virtual disk (SVD), for achieving high-performance home cloud environments. The proposed techniques are based on the workload characteristics, in which synchronous random writes dominate, while taking into consideration the characteristics of flash memory and storage stack of the virtualized systems. Unlike previous studies, SSD is used as a read-write cache in the proposed caching scheme to effectively mitigate the performance degradation of synchronous random writes. The prototype was evaluated with some realistic workloads, through which the developed scheme was shown to allow improvement of the storage access performance by 21% to 112%, with reduction in the number of erasures on SSD by about 56% on average.

PASS: a simple, efficient parallelism-aware solid state drive I/O scheduler

Emerging non-volatile memory technologies, especially flash-based solid state drives (SSDs), have increasingly been adopted in the storage stack. They provide numerous advantages over traditional mechanically rotating hard disk drives (HDDs) and have a tendency to replace HDDs. Due to the long existence of HDDs as primary building blocks for storage systems, however, much of the system software has been specially designed for HDD and may not be optimal for non-volatile memory media. Therefore, in order to realistically leverage its superior raw performance to the maximum, the existing upper layer software has to be re-evaluated or re-designed. To this end, in this paper, we propose PASS, an optimized I/O scheduler at the Linux block layer to accommodate the changing trend of underlying storage devices toward flash-based SSDs. PASS takes the rich internal parallelism in SSDs into account when dispatching requests to the device driver in order to achieve high performance. Specifically, it partitions the logical storage space into fixed-size regions (preferably the component package sizes) as scheduling units. These scheduling units are serviced in a round-robin manner and for every chance that the chosen dispatching unit issues only a batch of either read or write requests to suppress the excessive mutual interference. Additionally, the requests are sorted according to their visiting addresses while waiting in the dispatching queues to exploit high sequential performance of SSD. The experimental results with a variety of workloads have shown that PASS outperforms the four Linux off-the-shelf I/O schedulers by a degree of 3% up to 41%, while at the same time it improves the lifetime significantly, due to reducing the internal write amplification.

Data-assemblage: a translation-page-aware data block allocation strategy for flash-based solid state drives

Flash-based solid state drives (SSDs) are becoming popular as the storage media in recent years. In SSDs, translation pages normally store the address mapping information for data blocks. With the increasing capacity of SSDs, the management of translation pages is becoming a critical issue. In this paper, we present Data-Assemblage, a translation-page-aware data block allocation strategy for demand-based page-level address mappings in flash-based SSDs. Data-Assemblage is motivated by two observations: First, the translation page copy operations during garbage collection may significantly degrade the system performance. Second, the allocation of data blocks will directly impact the update operations in translation pages. By assembling write requests that share the same translation page into one data block, Data-Assemblage significantly reduces the page copies of translation pages and improves the average response time while retaining its space utilization and RAM cost. We evaluate Data-Assemblage using a set of benchmarks from both real-world and synthetic traces. Experimental results show that our scheme can achieve a 90.92 % reduction in the extra translation overhead and improve system performance by 22.14 % compared with the previous work.