54 lines
1.6 KiB
Markdown
54 lines
1.6 KiB
Markdown
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# JIT symbols
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[TOC]
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## Java JIT symbols
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On Android >= P, simpleperf supports profiling Java code, no matter whether it is executed by
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the interpreter, or JITed, or compiled into native instructions. So you don't need to do anything.
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For details on Android O and N, see
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[android_application_profiling.md](./android_application_profiling.md#prepare-an-android-application).
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## Generic JIT symbols
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Simpleperf supports picking up symbols from per-pid symbol map files, somewhat similar to what
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Linux kernel perftool does. Application should create those files at specific locations.
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### Symbol map file location for application
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Application should create symbol map files in its data directory.
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For example, process `123` of application `foo.bar.baz` should create
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`/data/data/foo.bar.baz/perf-123.map`.
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### Symbol map file location for standalone program
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Standalone programs should create symbol map files in `/data/local/tmp`.
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For example, standalone program process `123` should create `/data/local/tmp/perf-123.map`.
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### Symbol map file format
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Symbol map file is a text file.
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Every line describes a new symbol. Line format is:
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```
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<symbol-absolute-address> <symbol-size> <symbol-name>
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```
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For example:
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```
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0x10000000 0x16 jit_symbol_one
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0x20000000 0x332 jit_symbol_two
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0x20002004 0x8 jit_symbol_three
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```
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### Known issues
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Current implementation gets confused if memory pages where JIT symbols reside are reused by mapping
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a file either before or after.
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For example, if memory pages were first used by `dlopen("libfoo.so")`, then freed by `dlclose`,
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then allocated for JIT symbols - simpleperf will report symbols from `libfoo.so` instead.
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