Write back routine for JFFS2 efficient i/o

  • Authors:

  • Seung-Ho Lim;Sung-Hoon Baek;Joo-Young Hwang;Kyu-Ho Park

  • Affiliations:

  • Computer Engineering Research Laboratory, Department of Electrical Engineering and Computer Science, Korea Advanced Institute of Science and Technology;Computer Engineering Research Laboratory, Department of Electrical Engineering and Computer Science, Korea Advanced Institute of Science and Technology;Embedded OS Lab., Samsung Electronics;Computer Engineering Research Laboratory, Department of Electrical Engineering and Computer Science, Korea Advanced Institute of Science and Technology

  • Venue:
  • EUC'06 Proceedings of the 2006 international conference on Embedded and Ubiquitous Computing
  • Year:
  • 2006

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Abstract

When flash memory is used as a storage in embedded systems, block level translation layer is required between conventional filesystem and flash memory chips due to its physical characteristics. A far more efficient use of it is the design of a filesystem itself without no extra layer of translation. However, since flash filesystem does not use block device layer, it cannot utilize deferred I/O although deferred I/O enhances write latency by delaying the flushing jobs. Linux operating system generally uses the write back routine for deferred I/O using kernel thread, which writes back dirty pages and buffers through the block device layer. In this paper, we design and implement efficient I/O for JFFS2 flash filesystem based on flash memory. For this, we first analyze the write procedure of JFFS2 filesystem in detail, and derive the drawback and overhead. Then, we design the flash write back routine for deferred I/O. We apply it to the Linux JFFS2 by implementing fflush and flash_writeback kernel thread. The designed flash write back routine can reduce average write latency when the kernel buffers are enough to get the users data