orca/src/shared/renderer-heap-statistics.ts

/**
 * V8 heap statistics read from the renderer's own process.
 *
 * Why this exists rather than `window.performance.memory`: Blink quantizes that
 * API onto ~100 logarithmic buckets and caches each reading for ~20 minutes as a
 * Spectre mitigation. Measured here: a renderer climbing 1MB -> 93MB reported an
 * identical `usedJSHeapSize` on all 7 samples, so heap growth is invisible to it
 * at any sampling rate. `process.getHeapStatistics()` is exact and uncached, and
 * works in a sandboxed, context-isolated preload.
 *
 * Electron reports these in kilobytes; we keep that unit unconverted here.
 */
export type RendererHeapStatistics = {
  usedHeapKB: number
  totalHeapKB: number
  heapLimitKB: number
  /** Off-heap V8 allocations, which `usedJSHeapSize` never included. */
  mallocedKB: number
  /**
   * Blink's own allocator (DOM, layout), invisible to the V8 heap counters.
   * Optional: supplementary, so its absence must never discard the V8 numbers.
   */
  blinkAllocatedKB?: number
}