[Lldb-commits] [lldb] Fix dap stacktrace perf issue (PR #104874)
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lldb-commits at lists.llvm.org
Mon Aug 26 10:24:44 PDT 2024
jimingham wrote:
This is compiling the "get me extended backtrace info function". That's a ClangFunction, so we should only compile it once and then reuse it for the rest of the session. Is it possible we aren't reusing this? After all, this is a compile of a function that's pretty careful not to have a lot of external type references, so it is odd it's taking that long to compile!
Jim
> On Aug 23, 2024, at 7:09 PM, jeffreytan81 ***@***.***> wrote:
>
>
> And just for fun, here is an extreme one with 18 seconds of sampling time, 99.6% time is from this hot path. Note: they are all from linux machines because we only enable perf sampling by default for linux platform so we have no Mac data.
>
> # time of first sample : 2646936.334980
> # time of last sample : 2646954.518041
> # sample duration : 18183.061 ms
>
> 99.63% 0.00% lldb-dap lldb-dap [.] main
> |
> ---main
> lldb_dap::DAP::Loop()
> lldb_dap::DAP::HandleObject(llvm::json::Object const&)
> (anonymous namespace)::request_stackTrace(llvm::json::Object const&)
> |
> --99.60%--lldb::SBThread::GetCurrentExceptionBacktrace()
> lldb_private::Thread::GetCurrentExceptionBacktrace()
> lldb_private::Thread::GetCurrentException()
> lldb_private::ItaniumABILanguageRuntime::GetExceptionObjectForThread(std::shared_ptr<lldb_private::Thread>)
> |
> --99.60%--lldb_private::FunctionCaller::ExecuteFunction(lldb_private::ExecutionContext&, unsigned long*, lldb_private::EvaluateExpressionOptions const&, lldb_private::DiagnosticManager&, lldb_private::Value&)
> |
> |--44.33%--lldb_private::ClangFunctionCaller::CompileFunction(std::shared_ptr<lldb_private::Thread>, lldb_private::DiagnosticManager&)
> | |
> | |--39.56%--lldb_private::ClangExpressionParser::ParseInternal(lldb_private::DiagnosticManager&, clang::CodeCompleteConsumer*, unsigned int, unsigned int)
> | | |
> | | |--21.86%--clang::ParseAST(clang::Sema&, bool, bool)
> | | | |
> | | | |--17.47%--clang::Parser::ParseFirstTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&)
> | | | | clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&)
> | | | | clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*)
> | | | | clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*, clang::AccessSpecifier)
> | | | | clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec&,
> ...
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https://github.com/llvm/llvm-project/pull/104874
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