81 lines
3.0 KiB
Markdown
81 lines
3.0 KiB
Markdown
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# Linux Profiling
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Profiling code is enabled when the `use_allocator` variable in gyp is set to
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`tcmalloc` (currently the default) and `profiling` variable in gyp is set to
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`1`. That will build the tcmalloc library, including the cpu profiling and heap
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profiling code into edash-packager, e.g.
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GYP_DEFINES='profiling=1 use_allocator="tcmalloc"' gclient runhooks
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If the stack traces in your profiles are incomplete, this may be due to missing
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frame pointers in some of the libraries. A workaround is to use the
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`linux_keep_shadow_stacks=1` gyp option. This will keep a shadow stack using the
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`-finstrument-functions` option of gcc and consult the stack when unwinding.
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## CPU Profiling
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In order to enable cpu profiling, run edash-packager with the environment
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variable `CPUPROFILE` set to a filename. For example:
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CPUPROFILE=/tmp/cpuprofile out/Release/packager
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The cpu profile will be dumped periodically to the filename specified in the
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CPUPROFILE environment variable. You can then analyze the dumps using the pprof
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script (packager/third_party/tcmalloc/chromium/src/pprof). For example,
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pprof --gv out/Release/packager /tmp/cpuprofile
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This will generate a visual representation of the cpu profile as a postscript
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file and load it up using `gv`. For more powerful commands, please refer to the
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pprof help output and the google-perftools documentation.
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For further information, please refer to
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http://google-perftools.googlecode.com/svn/trunk/doc/cpuprofile.html.
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## Heap Profiling
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To turn on the heap profiler on edash-packager, use the `HEAPPROFILE`
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environment variable to specify a filename for the heap profile. For example:
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HEAPPROFILE=/tmp/heapprofile out/Release/packager
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The heap profile will be dumped periodically to the filename specified in the
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`HEAPPROFILE` environment variable. The dumps can be analyzed using the same
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command as cpu profiling above.
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For further information, please refer to
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http://google-perftools.googlecode.com/svn/trunk/doc/heapprofile.html.
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Some tests fork short-living processes which have a small memory footprint. To
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catch those, use the `HEAP_PROFILE_ALLOCATION_INTERVAL` environment variable.
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#### Dumping a profile of a running process
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To programmatically generate a heap profile before exit, use code like:
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#include "packager/third_party/tcmalloc/chromium/src/gperftools/heap-profiler.h"
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// "foobar" will be included in the message printed to the console
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HeapProfilerDump("foobar");
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Then add allocator.gyp dependency to the target with the above change:
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'conditions': [
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['profiling==1', {
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'dependencies': [
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'base/allocator/allocator.gyp:allocator',
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],
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}],
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],
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Or you can use gdb to attach at any point:
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1. Attach gdb to the process: `$ gdb -p 12345`
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2. Cause it to dump a profile: `(gdb) p HeapProfilerDump("foobar")`
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3. The filename will be printed on the console, e.g.
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"`Dumping heap profile to heap.0001.heap (foobar)`"
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## Reference
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[Linux Profiling in Chromium](https://chromium.googlesource.com/chromium/src/+/master/docs/linux_profiling.md)
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