File Fragmentation in Mobile Devices: Measurement, Evaluation, and Treatment

Cheng Ji, Li Pin Chang, Sangwook Shane Hahn, Sungjin Lee, Riwei Pan, Liang Shi*, Jihong Kim, Chun Jason Xue

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Mobile devices, such as smartphones, have become a necessity in our daily life. However, users may notice that after being used for a long time, mobile devices begin to exhibit a sluggish response. Based on an empirical study on a collection of aged smartphones, this work identified that file fragmentation is among the key factors that contribute to the progressive degradation of response time. This study takes a three-step approach: First, this study designed a set of reproducible file-system aging processes based on User-Interface (UI) script replay. Through the aging processes, it confirmed that file fragmentation quickly emerged, and SQLite files were among the most severely fragmented files. Second, based on the workloads of a selection of popular mobile applications, this study observed that file fragmentation did have an impact on user-perceived latencies. Specifically, the launching time of Chrome on an aged file system was 79 percent slower than it was on a pristine file system. Third, this study evaluated existing treatments of file fragmentation, including space preallocation, persistent journal, and file defragmentation to understand their efficacies and limitations. This study also evaluated a state-of-the-art copyless defragmenter, janusd, to show its advantage over the existing methods.

Original languageEnglish
Pages (from-to)2062-2076
Number of pages15
JournalIEEE Transactions on Mobile Computing
Issue number9
StatePublished - 1 Sep 2019


  • file fragmentation
  • flash memory
  • I/O performance
  • Measurements


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