Skip to content

Prefetcher

Jump to bottom
H. Joe Lee edited this page Jun 8, 2022 · 19 revisions

Prefetcher

Prefetcher promotes the BLOBs in Hermes to improve the I/O performance. It predicts the next BLOBs to get and place them in a queue.

Algorithms - what to prefetch

  • Size: Determine the size of a BLOB.
  • Frequency: Count the number of times a BLOB has been read since its creation.
  • Recency: Calculate the interval between the present and the last access time of a BLOB.
  • Importance: Use the importance score set by user.

For example, smaller size BLOB will require the fewer number of target buffers and can be prefetched with higher precedence. See [https://github.com/HDFGroup/hermes/wiki/Buffer-Organizer#blob-scoring](BLOB scoring)

Alogirthms - when to prefetch

  • Get API call.
Clone this wiki locally