Preemptible I/O Scheduling of Garbage Collection for Solid State Drives

Journal Article · Thu Feb 21 00:00:00 EST 2013 · IEEE Transations on Computer-Aided Design of Integrated Circuits and Systems

DOI:https://doi.org/10.1109/tcad.2012.2227479· OSTI ID:1565074

Lee, Junghee ^[1]; Kim, Youngjae ^[2]; Shipman, Galen M. ^[2]; Oral, Sarp ^[2]; Kim, Jongman ^[1]

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1. Georgia Inst. of Technology, Atlanta, GA (United States). School of Electrical and Computer Engineering
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Unlike hard disks, flash devices use out-of-place updates operations and require a garbage collection (GC) process to reclaim invalid pages to create free blocks. This GC process is a major cause of performance degradation when running concurrently with other I/O operations as internal bandwidth is consumed to reclaim these invalid pages. The invocation of the GC process is generally governed by a low watermark on free blocks and other internal device metrics that different workloads meet at different intervals. This results in an I/O performance that is highly dependent on workload characteristics. In this paper, we examine the GC process and propose a semipreemptible GC (PGC) scheme that allows GC processing to be preempted while pending I/O requests in the queue are serviced. Moreover, we further enhance flash performance by pipelining internal GC operations and merge them with pending I/O requests whenever possible. Our experimental evaluation of this semi-PGC scheme with realistic workloads demonstrates both improved performance and reduced performance variability. Write-dominant workloads show up to a 66.56% improvement in average response time with a 83.30% reduced variance in response time compared to the non-PGC scheme. In addition, we explore opportunities of a new NAND flash device that supports suspend/resume commands for read, write, and erase operations for fully PGC (F-PGC). Our experiments with an F-PGC enabled flash device show that request response time can be improved by up to 14.57% compared to semi-PGC.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1565074
• Journal Information: IEEE Transations on Computer-Aided Design of Integrated Circuits and Systems, Journal Name: IEEE Transations on Computer-Aided Design of Integrated Circuits and Systems Journal Issue: 2 Vol. 32; ISSN 0278-0070
• Publisher: IEEE
• Country of Publication: United States
• Language: English

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