Jordan Delong
363d1bb20f
This change is mostly for FB internal organizational reasons. Building is not effected beyond the fact that the target now lands in hphp/hhvm/hhvm rather than src/hhvm/hhvm.
63 linhas
2.0 KiB
Plaintext
63 linhas
2.0 KiB
Plaintext
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<h2>Debugging Memory Leaks</h2>
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First of all, we need unit tests to verify different classes and functions
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(esp. extension functions) don't have memory leaks by running under valgrind
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like this:
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GLIBCXX_FORCE_NEW=1 \
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valgrind --suppressions=../bin/valgrind.suppression --tool=memcheck \
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--leak-check=full --num-callers=30 --max-stackframe=3000000 \
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test/test TestExtFoo::test_ext_bar
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When it comes to server running, it becomes impossible to run valgrind or
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heap profiler that slows down request handling very much. Here's the procedure
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to run built-in memory leak detection against a live server:
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1. Turn on heap profiler
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Build the server (both HPHP and www) with modification of rules.mk:
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DEBUG=1
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#GOOGLE_CPU_PROFILER = 1
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GOOGLE_HEAP_PROFILER = 1
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This turns off CPU profiler and turns on heap profiler that gives us malloc()
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hooks for our own sampling based leak detection. We also need to turn on DEBUG
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to generate readable stacktraces.
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2. Turn off mt_allocator
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Run server with <b>GLIBCXX_FORCE_NEW=1</b>. This environment variable turns
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off STL's mt_allocator, which doesn't call free() when some STL objects are
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destructed.
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3. Initialize long-living objects
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Let the server run for a few minutes, until APC is mostly updated. Otherwise,
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APC objects may be reported as leaked items.
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4. Turn on leak detection
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Hit the server to turn on leak detection:
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GET http://[server]:8088/leak-on?sampling=500
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The higher the sampling rate, the least impact leak detection has on server
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running, but it will take longer to collect leaked items. 500 is a good rate
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in our debugging process.
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5. Report leaks
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Wait for minutes long, or even hours long, depending on how rare the leak
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happens. Then hit the server to turn off leak detection and to report leaks:
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GET http://[server]:8088/leak-off > leak_report
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6. Examine output
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The output should have all leaked items. Sometimes some stacks are not
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fully translated, and a manual translation needs to be done like this:
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./www --mode translate <hex-coded-stacktrace>
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