CompileThreshold，Tier2CompileThreshold，Tier3CompileThreshold和Tier4CompileThreshold控制什么？ [英] What does CompileThreshold, Tier2CompileThreshold, Tier3CompileThreshold and Tier4CompileThreshold control?
问题描述
HotSpot的分层编译使用解释器，直到调用阈值（对于方法）或迭代（对于循环）触发具有自我分析的客户端编译。使用客户端编译，直到另一个调用或迭代阈值触发服务器编译。
HotSpot's tiered compilation uses the interpreter until a threshold of invocations (for methods) or iterations (for loops) triggers a client compilation with self-profiling. The client compilation is used until another threshold of invocations or iterations triggers a server compilation.
打印HotSpot的标志使用-XX显示以下标志值：+ TieredCompilation。
Printing HotSpot's flags shows the following flag values with -XX:+TieredCompilation.
intx CompileThreshold = 10000 {pd product}
intx Tier2CompileThreshold = 0 {product}
intx Tier3CompileThreshold = 2000 {product}
intx Tier4CompileThreshold = 15000 {product}
只有客户端和服务器编译器有太多标志。这些标志控制了哪些编译器？如果不是客户端和服务器，那么附加编译器的目的是什么？
There are too many flags for just a client and server compiler. What compilers are controlled by these flags? If not client and server, what is the purpose of the additional compilers?
在这种情况下是否忽略了CompileThreshold和Tier2CompileThreshold？触发客户端编译时Tier3CompileThreshold控制什么？触发服务器编译时Tier4CompileThreshold控制什么？
Are CompileThreshold and Tier2CompileThreshold ignored in this case? What does Tier3CompileThreshold control when a client compilation is triggered? What does Tier4CompileThreshold control when a server compilation is triggered?
推荐答案
advancedThresholdPolicy.hpp 讨论了不同的编译器层和阈值。请参阅该文件以进行更深入的讨论。
The comments in advancedThresholdPolicy.hpp discuss the different compiler tiers and the thresholds. See that file for a deeper discussion.
系统支持5个执行级别：
The system supports 5 execution levels:
- 第0层 - 解释器
- 第1层 - 完全优化的C1（无分析）
- 第2层 - 带调用和备份计数器的C1
- 第3层 - 具有完整性能分析的C1（2级+ MDO）
- 第4层 - C2
- Tier 0 - interpreter
- Tier 1 - C1 with full optimization (no profiling)
- Tier 2 - C1 with invocation and backedge counters
- Tier 3 - C1 with full profiling (level 2 + MDO)
- Tier 4 - C2
C1是客户端编译器。 C2是服务器编译器。
C1 is the client compiler. C2 is the server compiler.
在常见情况下，编译为：0→3→4。根据C1和C2队列长度使用非典型情况。当C2队列长度太长时使用第2层，以便该方法可以执行约30％的速度，直到C2可以处理分析信息。如果确定该方法是微不足道的，那么它将使用第1层编译，因为它将生成与第4层相同的代码。
In the common case, the compilation goes: 0 → 3 → 4. Atypical cases are used based on C1 and C2 queue lengths. Tier 2 is used when the C2 queue length is too long so that the method can execute about 30% faster until the C2 can process the profiling information. If the method is determined to be trivial, then it is compiled with Tier 1 since it will produce the same code as Tier 4.
阈值是根据长度动态调整的C1和C2队列。
Thresholds are dynamically adjusted based on the length of the C1 and C2 queues.
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