Idle time garbage collection scheduling

Abstract

Efficient garbage collection is increasingly important in today's managed language runtime systems that demand low latency, low memory consumption, and high throughput. Garbage collection may pause the application for many milliseconds to identify live memory, free unused memory, and compact fragmented regions of memory, even when employing concurrent garbage collection. In animation-based applications that require 60 frames per second, these pause times may be observable, degrading user experience. This paper introduces idle time garbage collection scheduling to increase the responsiveness of applications by hiding expensive garbage collection operations inside of small, otherwise unused idle portions of the application's execution, resulting in smoother animations. Additionally we take advantage of idleness to reduce memory consumption while allowing higher memory use when high throughput is required. We implemented idle time garbage collection scheduling in V8, an open-source, production JavaScript virtual machine running within Chrome. We present performance results on various benchmarks running popular webpages and show that idle time garbage collection scheduling can significantly improve latency and memory consumption. Furthermore, we introduce a new metric called frame time discrepancy to quantify the quality of the user experience and precisely measure the improvements that idle time garbage collection scheduling provides for a WebGL-based game benchmark. Idle time garbage collection scheduling is shipped and enabled by default in Chrome.

Learned garbage collection

“…Garbage collection is an active area of research [2,3,23,34]. [26] proposes new user-facing APIs to more easily (manually) customize garbage collectors.…”

Phase-Aware Web Browser Power Management on HMP Platforms

“…A number of recent publications have targeted the performance of browsers [2,7,10,22,26] with the aim of improving the user experience. However, very few studies have addressed the issue of web browser power consumption, although battery lifetime is an important metric when measuring the usability of mobile devices.…”

Cross-component garbage collection

“…Compaction is used to reduce memory fragmentation in the old generation and is done in parallel to reduce the time spent where the main thread is stopped. V8 takes advantage of idle time garbage collection scheduling [Degenbaev et al 2016] to perform as much garbage collection work during idle time as possible.…”

“…V8 serves as master tracer initiating the garbage collection based on heap-sizing heuristics[Degenbaev et al 2016;White et al 2013] that consider the current size of the V8 and Blink managed heaps. The generic methods advance_marking and incremental_step(deadline) directly map to the existing incremental marking code in V8.…”