Optimize NMethod type check#1701
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apangin
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Mar 18, 2026
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| if (nm->isNMethod()) { |
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No actual changes; just swapped nm->isInterpreter() and nm->isNMethod() branches.
fandreuz
approved these changes
Mar 18, 2026
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Description
Currently,
NMethod::isInterpreter,isNMethod,isStubandisVTableStubare implemented by comparing the name usingstrcmp/strncmp. We can make the check faster by inlining string comparison.Also, for interpreted frames, instead of checking NMethod name we could check NMethod pointer itself, because Interpreter is a singleton.
On some benchmarks, improvement in average stack walking speed can reach 10% as measured by
features=stats:Related issues
#1662
Motivation and context
This change was inspired by @fandreuz's PR: #1662
However, what I'm not happy about in that implementation is that it makes
isTypemethods stateful. I found that the actual performance issue was not in the string comparison itself, but rather in an indirect call to a standard library function. I went further and replacedisInterpreterwith a single pointer comparison, since HotSpot has exactly one Code Blob with the nameInterpreter.By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.