LDF-CLOCK: The least-dirty-first CLOCK replacement policy for PCM-based swap devices

Seunghoon Yoo, Eunji Lee, Hyokyung Bahn

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Phase-change memory (PCM) is a promising technology that is anticipated to be used in the memory hierarchy of future computer systems. However, its access time is relatively slower than DRAM and it has limited endurance cycle. Due to this reason, PCM is being considered as a high-speed storage medium (like swap device) or long-latency memory. In this paper, we adopt PCM as a virtual memory swap device and present a new page replacement policy that considers the characteristics of PCM. Specifically, we aim to reduce the write traffic to PCM by considering the dirtiness of pages when making a replacement decision. The proposed replacement policy tracks the dirtiness of a page at the granularity of a sub-page and replaces the least dirty page among pages not recently used. Experimental results with various workloads show that the proposed policy reduces the amount of data written to PCM by 22.9% on average and up to 73.7% compared to CLOCK. It also extends the lifespan of PCM by 49.0% and reduces the energy consumption of PCM by 3.0% on average.

Original languageEnglish
Pages (from-to)68-76
Number of pages9
JournalJournal of Semiconductor Technology and Science
Issue number1
StatePublished - Feb 2015

Bibliographical note

Funding Information:
This work wasupportedby the National Research Foundation (NRF) grant funded by the Korea government (MEST) (No. 2011-0028825).

Publisher Copyright:
© 2015, Institute of Electronics Engineers of Korea. All rights reserved.


  • Phase-change memory
  • Replacement policy
  • Swap device
  • Virtual memory


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