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/ClangdServer.cpp b/clang-tools-extra/clangd/ClangdServer.cpp
index 035f3ee..ba9336f 100644
--- a/clang-tools-extra/clangd/ClangdServer.cpp
+++ b/clang-tools-extra/clangd/ClangdServer.cpp
@@ -15,6 +15,8 @@
#include "llvm/ADT/ArrayRef.h"
#include "llvm/Support/Errc.h"
#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/FormatProviders.h"
+#include "llvm/Support/FormatVariadic.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/raw_ostream.h"
#include <future>
@@ -98,7 +100,8 @@
Workers.reserve(AsyncThreadsCount);
for (unsigned I = 0; I < AsyncThreadsCount; ++I) {
- Workers.push_back(std::thread([this]() {
+ Workers.push_back(std::thread([this, I]() {
+ llvm::set_thread_name(llvm::formatv("scheduler/{0}", I));
while (true) {
UniqueFunction<void()> Request;