Optimised Linux swap system for flash memory

Lin, Mingwei; Chen, S.; Lv, Guangzhen; Zhou, Zhen

doi:10.1049/el.2011.0621

Cited by 13 publications

(8 citation statements)

References 6 publications

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“…Ko et al proposed a new Linux swap system called LOBI [4], which adopts a block-aligned swap-in read-ahead algorithm to reduce the number of cleaned blocks and delay the execution of garbage collection operation. Lin et al proposed a Linux swap system, called SGBI [1], where Linux kernel 2.6 manages the flash memory-based swap space directly without FTL. This system focuses on exploiting a garbage collection policy and an efficient swap-in read-ahead algorithm.…”

Section: A Existing Work On Swap Space Management Schemementioning

confidence: 99%

“…Due to limited memory resource of portable consumer electronics, portable consumer electronics currently exploit efficient Linux swap systems [1]- [4] considering flash memory as swap space as a cost effective solution to extend limited memory space. The flash memory-based swap space is always used up in a short period of time due to the out-of-place update scheme used to solve the erase-before-write constraint of flash memory.…”

Section: Introductionmentioning

confidence: 99%

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Flash-aware linux swap system for portable consumer electronics

Lin

Chen

2012

IEEE Trans. Consumer Electron.

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Because of limited memory resource of portable consumer electronics, portable consumer electronics currently exploit swap space with flash memory as a cost effective solution to extend limited memory space. Original swap space management scheme used in Linux for magnetic disk is not available to flash memory-based swap space due to the distinct characteristics of flash memory.In this paper, we propose a flash-aware Linux swap system, called FLSS, which adopts Linux kernel 2.6 to manage flash memory-based swap space directly without FTL. We introduce: 1) a partial block alignment scheme to perform an efficient swap-in read-ahead algorithm, 2) a swap-aware victim block selection method and the redefined concept of hot page and cold page to design a swap-aware garbage collection policy called SACATA, and 3) the notion of overage as well as the notion of frozen applied to blocks to exploit a wear leveling-aware block management scheme. Experimental results show that the proposed FLSS greatly outperforms existing swap space management techniques and evaluate the effectiveness of proposed SACATA 1 .

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Section: A Existing Work On Swap Space Management Schemementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Flash-aware linux swap system for portable consumer electronics

Lin

Chen

2012

IEEE Trans. Consumer Electron.

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“…SAGC works well for the Linux swap system because it considers the used page replacement algorithm, but it does not consider the degree of wear-levelling during the selection of victim blocks. Lin et al also proposed a swap-aware garbage collection policy, called SG [1], which does not consider the invalidation times of invalid pages in each block during the selection of victim blocks.…”

mentioning

confidence: 99%

“…We have implemented the SCATA policy integrated into SGBI [1] and collected swap I/O traces from the Linux kernel. Trace-driven simulations show that the proposed policy outperforms existing garbage collection policies under the Linux swap system.…”

mentioning

confidence: 99%

“…The performance metrics we used are the number of erase operations, the number of copy operations, the degree of wear-levelling [1], and the number of garbage collection operations performed. Since garbage collection operation consists of lots of valid page copy operations and block erase operation, an efficient garbage collection should eliminate the number of erase operations and page copy operations.…”

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confidence: 99%

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Garbage collection policy for flash-aware Linux swap system

Lin

Chen

et al. 2011

Electron. Lett.

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Proposed is a swap-aware garbage collection policy, called SCATA, for a flash-aware Linux swap system. SCATA not only introduces an improved victim block selection method to reduce cleaning cost and improve the degree of wear-levelling, but also redefines the concept of hot page and cold page according to the least-recently-used page replacement algorithm and clusters hot pages separately from cold pages, and then redistributes them to different free blocks during the migration step of garbage collection operation to reduce cleaning cost and obtain much more free space. Swap I/O traces from the Linux kernel have been collected and trace-driven simulations performed, which show that the proposed policy greatly outperforms existing garbage collection policies.Introduction: As a result of the limited memory resource of embedded systems, embedded systems exploit an efficient Linux swap system [1 -3] considering flash memory as swap storage as a cost-effective solution to extend limited memory space. All write operations of flash-memorybased swap storage are requested during the page replacement operation. Since a page slot of which the size is 4 K bytes is always allocated to accommodate the page swapped out from main memory during the page replacement operation and out-of-place update scheme is adopted to solve the erase-before-write constraint of flash memory, the flashmemory-based swap area is always used up in a short period of time. In this case, an efficient garbage collection policy for the Linux swap system considering flash memory as swap storage is needed to reclaim garbage and obtain free blocks.The cleaning cost and the degree of wear-levelling are two primary concerns of a garbage collection policy. Namely, an efficient garbage collection policy should minimise the cleaning cost of garbage collection and wear down all blocks as evenly as possible. A number of garbage collection policies have been studied. Wu et al. proposed the greedy algorithm (GR) [4] to select victim blocks with the least utilisation for erasure, hoping to obtain free space as much as possible with the least cleaning cost. The greedy algorithm can be implemented simply, but does not consider the degree of wear-levelling. The cost-benefit algorithm (CB) [5] proposed by Kawaguchi et al. adopts the benefit-cost ratio used in the formal discipline of cost-benefit analysis to choose victim blocks with highest benefit-cost for erasure. Chiang et al. proposed the cost age time (CAT) policy [6], which extends CB by considering the erasure count of each block during the selection of victim blocks in order to improve the degree of wear-levelling. To reduce cleaning cost and reclaim the largest amount of invalid pages to obtain the largest amount of free space, the CAT policy clusters hot pages separately from cold pages and redistributes them to different free blocks during the migration step of the garbage collection operation. Han et al. proposed the cost-agetime with age-sort (CATA) algorithm [7] for which the selection method of victim bloc...

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