Performance tracing facility for clangd.
Summary:
This lets you visualize clangd's activity on different threads over time,
and understand critical paths of requests and object lifetimes.
The data produced can be visualized in Chrome (at chrome://tracing), or
in a standalone copy of catapult (http://github.com/catapult-project/catapult)
This patch consists of:
- a command line flag "-trace" that causes clangd to emit JSON trace data
- an API (in Trace.h) allowing clangd code to easily add events to the stream
- several initial uses of this API to capture JSON-RPC requests, builds, logs
Example result: https://photos.app.goo.gl/12L9swaz5REGQ1rm1
Caveats:
- JSON serialization is ad-hoc (isn't it everywhere?) so the API is
limited to naming events rather than attaching arbitrary metadata.
I'd like to fix this (I think we could use a JSON-object abstraction).
- The recording is very naive: events are written immediately by
locking a mutex. Contention on the mutex might disturb performance.
- For now it just traces instants or spans on the current thread.
There are other things that make sense to show (cross-thread flows,
non-thread resources such as ASTs). But we have to start somewhere.
Reviewers: ioeric, ilya-biryukov
Subscribers: cfe-commits, mgorny
Differential Revision: https://reviews.llvm.org/D39086
llvm-svn: 317193
diff --git a/clang-tools-extra/clangd/ClangdUnit.cpp b/clang-tools-extra/clangd/ClangdUnit.cpp
index 53170a5..82ea54d 100644
--- a/clang-tools-extra/clangd/ClangdUnit.cpp
+++ b/clang-tools-extra/clangd/ClangdUnit.cpp
@@ -10,6 +10,7 @@
#include "ClangdUnit.h"
#include "Logger.h"
+#include "Trace.h"
#include "clang/Frontend/CompilerInstance.h"
#include "clang/Frontend/CompilerInvocation.h"
#include "clang/Frontend/FrontendActions.h"
@@ -1285,6 +1286,7 @@
return OldPreamble;
}
+ trace::Span Tracer(llvm::Twine("Preamble: ") + That->FileName);
std::vector<DiagWithFixIts> PreambleDiags;
StoreDiagsConsumer PreambleDiagnosticsConsumer(/*ref*/ PreambleDiags);
IntrusiveRefCntPtr<DiagnosticsEngine> PreambleDiagsEngine =
@@ -1330,9 +1332,13 @@
}
// Compute updated AST.
- llvm::Optional<ParsedAST> NewAST =
- ParsedAST::Build(std::move(CI), PreambleForAST, SerializedPreambleDecls,
- std::move(ContentsBuffer), PCHs, VFS, That->Logger);
+ llvm::Optional<ParsedAST> NewAST;
+ {
+ trace::Span Tracer(llvm::Twine("Build: ") + That->FileName);
+ NewAST = ParsedAST::Build(
+ std::move(CI), PreambleForAST, SerializedPreambleDecls,
+ std::move(ContentsBuffer), PCHs, VFS, That->Logger);
+ }
if (NewAST) {
Diagnostics.insert(Diagnostics.end(), NewAST->getDiagnostics().begin(),