问题描述
我听说 JIT 会自动内联小方法，例如 getter(它们大约有 5 个字节).边界是什么?有JVM标志吗?
I've heard that JIT automatically inlines small methods, like getters (they have about 5 bytes). What is the boundary? Is there any JVM flag?
推荐答案
HotSpot JIT 内联策略比较复杂.它涉及许多启发式方法，如调用方方法大小、被调用方方法大小、IR 节点数、内联深度、调用数、调用站点数、抛出数、方法签名等.
HotSpot JIT inlining policy is rather complicated. It involves many heuristics like caller method size, callee method size, IR node count, inlining depth, invocation count, call site count, throw count, method signatures etc.
访问器方法(getter/setter)和普通方法(字节码计数小于 6)会跳过一些限制.
Some limits are skipped for accessor methods (getters/setters) and for trivial methods (bytecode count less than 6).
相关源码大多在bytecodeInfo.cpp.
请参阅 InlineTree::try_to_inline、should_inline、should_not_inline 函数.
The related source code is mostly in bytecodeInfo.cpp.
See InlineTree::try_to_inline, should_inline, should_not_inline functions.
控制内联的主要 JVM 标志是
The main JVM flags to control inlining are
-XX:MaxInlineLevel (maximum number of nested calls that are inlined)
-XX:MaxInlineSize (maximum bytecode size of a method to be inlined)
-XX:FreqInlineSize (maximum bytecode size of a frequent method to be inlined)
-XX:MaxTrivialSize (maximum bytecode size of a trivial method to be inlined)
-XX:MinInliningThreshold (min. invocation count a method needs to have to be inlined)
-XX:LiveNodeCountInliningCutoff (max number of live nodes in a method)
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