QA/Automation/Projects/Addons/MemChaser/Future Features

Circular Buffer

Usage/Overview

• Main data structure for graphs
• Stores temporary GC (and CC,etc.) values
• Conceptually is a linked list with a cycle from the tail to head, but it would be implemented using an array in JavaScript

Requirements

• Have as little impact on garbage collection as possible
• Have read/write capabilities with events emitted from writes
• Read operations should not post-increment head index and should not delete the element being read

Current Proposal

Source

https://github.com/dglol/memchaser/blob/circular-buffer/extension/lib/circular-buffer.js

Fields

• head
  • index for the head/front of the buffer

• tail
  • index for the tail/back of the buffer

• buffer
  • array building block for this data structure

Methods

• CircularBuffer(length) (Constructor)
  • only required a length to initialize
  • length defaults to 1 if a undefined value or negative number is given

• size() (Necessary)
  • returns the size of the buffer

• read([index]) (Necessary)
  • returns data from [head + index] if index is given
  • else it returns the data at [head] (i.e. index = 0)

• write(data) (Necessary)
  • writes data at the [tail] then increments tail index by one
  • emits an event 'bufferWrite'

• clear() (Optional)
  • resets the buffer, head index and tail index

• dequeue() (Optional)
  • reads from [head], removes the data at [head] and increments head by one

• back() (Optional)
  • reads from [tail]

Discussion items

JSON Blob vs Separate Buffers

• A JSON Blob of all the data ({gc: , cc:, etc}) has less overhead but writes would have to be synchronous
• GC and related data occur at different times, so separate buffers allows asynchronous writing

Memory Report per Compartment

Blocked by https://bugzilla.mozilla.org/show_bug.cgi?id=687724