未加星标

How Facebook Redesigned the HHVM JIT Compiler for Performance

字体大小 | |
[开发(php) 所属分类 开发(php) | 发布者 店小二04 | 时间 2016 | 作者 红领巾 ] 0人收藏点击收藏

In the Summer of 2013, Facebook engineers started a major redesign of theHHVM JIT compiler that brought an overall 15% reduction of CPU usage on Facebook’s web servers. Facebook engineer Guilherme Ottoni has recently described how Facebook achieved that result by backing profile-guided optimizations (PGO) into their JIT compiler.

Profile-guided optimization is a technique that aims to use runtime profiling, such as identifying parts of the code that are executed more frequently, to improve code generation. PGO is particularly well-suited for integration in dynamic and JIT compilers given the integrated nature of the compiler and the runtime environment.

Facebook engineers focused on two main goals: using profile information to optimize decisions that are made at compilation time and to help the compiler identify larger type-specialized compilation regions, i.e., regions where generated code can be optimized for a given known type, thus avoiding the cost of type checks. To make this possible, the HHVM JIT compiler had to learn how to translate arbitrary code regions instead of just tracelets , which are very basic type-specialized blocks that are independently translated to machine code. Tracelets do not grow arbitrarily, since by their definition tracelets end whenever the type for an input to the block cannot be determined, or when the JIT compiler cannot determine the direction of a branch.

The first step taken by Facebook engineers to generalize tracelets was to assemble several of them together based on profiling information. By doing this, they could reduce the overhead of entering and exiting different tracelets, and additionally implement more advanced cross-tracelet optimizations, such as hoisting loop-invariant computations out of loops.


How Facebook Redesigned the HHVM JIT Compiler for Performance

Building larger regions out of basic tracelets had the advantage of not violating any assumptions in the existing JIT optimizer and backend, which were tightly designed around that concept. In a second phase, though, Facebook engineers started a major redesign of those components to be able to handle regions with arbitrary control flow. This effort, completed by the spring of 2015, significantly improved JIT compilation performance by reducing CPU usage by 15%, thus trebling the improvement gained in the first phase.

本文开发(php)相关术语:php代码审计工具 php开发工程师 移动开发者大会 移动互联网开发 web开发工程师 软件开发流程 软件开发工程师

主题: FacebookCPUJIT
分页:12
转载请注明
本文标题:How Facebook Redesigned the HHVM JIT Compiler for Performance
本站链接:http://www.codesec.net/view/480127.html
分享请点击:


1.凡CodeSecTeam转载的文章,均出自其它媒体或其他官网介绍,目的在于传递更多的信息,并不代表本站赞同其观点和其真实性负责;
2.转载的文章仅代表原创作者观点,与本站无关。其原创性以及文中陈述文字和内容未经本站证实,本站对该文以及其中全部或者部分内容、文字的真实性、完整性、及时性,不作出任何保证或承若;
3.如本站转载稿涉及版权等问题,请作者及时联系本站,我们会及时处理。
登录后可拥有收藏文章、关注作者等权限...
技术大类 技术大类 | 开发(php) | 评论(0) | 阅读(42)