Android ASHMEM

1 Anonymous Shared Memory

  1. IPC mechanism of Android.
  2. ashmem allows processes which are not related by ancestry to share memory areas by name. sharing via file descriptors. Released automatically.
  3. Android discarded SysV IPC mechanisms, which can lead to resource leakage in the kernel.
  4. Similar to POSIX SHM, differences:
  5. Uses reference counting to destroy the memory regions
  6. Shrink mapped regions when the system needs memory
  7. To shrink a region it must be unpinned
  8. First process creates region, uses Binder to share descriptor with other processes
  9. System services rely on ashmem
  10. Surface Flinger, Audio Flinger
  11. Driver included in the staging tree
  12. source code mm/ashmem.c

2 Reading beyond the Lectures

3 End

Copyright © 2019 www.wright.edu/~pmateti • 2019-03-05