Leveraging Architectural Support of Three Page Sizes with Trident

TL;DR

This paper demonstrates that supporting multiple large page sizes, especially 1GB pages, with proper system software support can significantly improve performance for memory-intensive applications on modern processors.

Contribution

It introduces Trident, a Linux system that dynamically allocates 1GB, 2MB, and 4KB pages to optimize performance, and TridentPV, which virtualizes 1GB pages efficiently.

Findings

1GB pages can outperform 2MB pages with proper support.

Trident improves application performance by 18% on average.

Supporting multiple large page sizes is practically beneficial.

Abstract

Large pages are commonly deployed to reduce address translation overheads for big-memory workloads. Modern x86-64 processors from Intel and AMD support two large page sizes -- 1GB and 2MB. However, previous works on large pages have primarily focused on 2MB pages, partly due to lack of substantial evidence on the profitability of 1GB pages to real-world applications. We argue that in fact, inadequate system software support is responsible for a decade of underutilized hardware support for 1GB pages. Through extensive experimentation on a real system, we demonstrate that 1GB pages can improve performance over 2MB pages, and when used in tandem with 2MB pages for an important set of applications; the support for the latter is crucial but missing in current systems. Our design and implementation of \trident{} in Linux fully exploit hardware supported large pages by dynamically and transparently allocating 1GB, 2MB, and 4KB pages as deemed suitable. \trident{} speeds up eight memory-intensive applications by {$18\%$}, on average, over Linux's use of 2MB pages. We also propose \tridentpv{}, an extension to \trident{} that effectively virtualizes 1GB pages via copy-less promotion and compaction in the guest OS. Overall, this paper shows that even GB-sized pages have considerable practical significance with adequate software enablement, in turn motivating architects to continue investing/innovating in large pages.