(0.46.0) Changes to the code cache repository allocation code #19575
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In order to eliminate helper trampolines, OpenJ9 tries to allocate the code cache in the vicinity of the JIT dll. This intention is signalled by using a `preferredStartAddress` when calling `allocateCodeCacheSegment()`. Currently, only x86-64 uses this approach. This commit implements the following changes: - For Linux, we increase the search space to almost 2GB. Also, we prefer to start with an approach that uses the `smaps` pseudofile to find memory ranges where the code cache could be allocated. - For Windows, we keep a smaller memory search space because smaps are not available to speed up the search process. - We compute a preferred alignment and pass that to the VM. For x86-64 this alignment is 2 MB, i.e. the size of large pages used by the Transparent Huge Page (THP) mechanism. The alignment is relevant only when preferredStartAddress is provided. - For Linux we provide a hint to the OS (with madvise) that we prefer the usage of THP for the span of the code cache repository. Signed-off-by: Marius Pirvu <[email protected]>
Signed-off-by: Marius Pirvu <[email protected]>
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In order to eliminate helper trampolines, OpenJ9 tries to allocate the code cache in the vicinity of the JIT dll. This intention is signalled by using a preferredStartAddress when calling allocateCodeCacheSegment(). Currently, only x86-64 uses this approach.
This commit implements the following changes: