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/ProtocolHandlers.cpp b/clang-tools-extra/clangd/ProtocolHandlers.cpp
index 6dcc3f5..507fc42 100644
--- a/clang-tools-extra/clangd/ProtocolHandlers.cpp
+++ b/clang-tools-extra/clangd/ProtocolHandlers.cpp
@@ -11,6 +11,7 @@
#include "ClangdLSPServer.h"
#include "ClangdServer.h"
#include "DraftStore.h"
+#include "Trace.h"
using namespace clang;
using namespace clang::clangd;
@@ -30,7 +31,10 @@
auto *Callbacks = this->Callbacks;
Dispatcher.registerHandler(
Method, [=](RequestContext C, llvm::yaml::MappingNode *RawParams) {
- if (auto P = std::decay<Param>::type::parse(RawParams, *Out)) {
+ if (auto P = [&] {
+ trace::Span Tracer("Parse");
+ return std::decay<Param>::type::parse(RawParams, *Out);
+ }()) {
(Callbacks->*Handler)(std::move(C), *P);
} else {
Out->log("Failed to decode " + Method + " request.\n");