[PATCH] D96027: [clangd] Trace queue state for each TUScheduler action.

[Sam McCall via Phabricator via cfe-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rGfed995ef9020: [clangd] Trace queue state for each TUScheduler action. (authored by sammccall).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D96027/new/

https://reviews.llvm.org/D96027

Files:
  clang-tools-extra/clangd/TUScheduler.cpp


Index: clang-tools-extra/clangd/TUScheduler.cpp
===================================================================
--- clang-tools-extra/clangd/TUScheduler.cpp
+++ clang-tools-extra/clangd/TUScheduler.cpp
@@ -465,6 +465,7 @@
     std::string Name;
     steady_clock::time_point AddTime;
     Context Ctx;
+    llvm::Optional<Context> QueueCtx;
     llvm::Optional<UpdateType> Update;
     TUScheduler::ASTActionInvalidation InvalidationPolicy;
     Canceler Invalidate;
@@ -507,7 +508,7 @@
   /// None means no builds yet, null means there was an error while building.
   /// Only written by ASTWorker's thread.
   llvm::Optional<std::shared_ptr<const PreambleData>> LatestPreamble;
-  std::queue<Request> PreambleRequests; /* GUARDED_BY(Mutex) */
+  std::deque<Request> PreambleRequests; /* GUARDED_BY(Mutex) */
   /// Signaled whenever LatestPreamble changes state or there's a new
   /// PreambleRequest.
   mutable std::condition_variable PreambleCV;
@@ -826,9 +827,10 @@
   }
   {
     std::lock_guard<std::mutex> Lock(Mutex);
-    PreambleRequests.push({std::move(Task), std::move(TaskName),
-                           steady_clock::now(), Context::current().clone(),
-                           llvm::None, TUScheduler::NoInvalidation, nullptr});
+    PreambleRequests.push_back({std::move(Task), std::move(TaskName),
+                                steady_clock::now(), Context::current().clone(),
+                                llvm::None, llvm::None,
+                                TUScheduler::NoInvalidation, nullptr});
   }
   PreambleCV.notify_all();
   RequestsCV.notify_all();
@@ -1023,9 +1025,34 @@
       std::tie(Ctx, Invalidate) = cancelableTask(
           /*Reason=*/static_cast<int>(ErrorCode::ContentModified));
     }
+    // Trace the time the request spends in the queue, and the requests that
+    // it's going to wait for.
+    llvm::Optional<Context> QueueCtx;
+    if (trace::enabled()) {
+      // Tracers that follow threads and need strict nesting will see a tiny
+      // instantaneous event "we're enqueueing", and sometime later it runs.
+      WithContext WC(Ctx.clone());
+      trace::Span Tracer("Queued:" + Name);
+      if (Tracer.Args) {
+        if (CurrentRequest)
+          SPAN_ATTACH(Tracer, "CurrentRequest", CurrentRequest->Name);
+        llvm::json::Array PreambleRequestsNames;
+        for (const auto &Req : PreambleRequests)
+          PreambleRequestsNames.push_back(Req.Name);
+        SPAN_ATTACH(Tracer, "PreambleRequestsNames",
+                    std::move(PreambleRequestsNames));
+        llvm::json::Array RequestsNames;
+        for (const auto &Req : Requests)
+          RequestsNames.push_back(Req.Name);
+        SPAN_ATTACH(Tracer, "RequestsNames", std::move(RequestsNames));
+      }
+      // For tracers that follow contexts, keep the trace span's context alive
+      // until we dequeue the request, so they see the full duration.
+      QueueCtx = Context::current().clone();
+    }
     Requests.push_back({std::move(Task), std::string(Name), steady_clock::now(),
-                        std::move(Ctx), Update, Invalidation,
-                        std::move(Invalidate)});
+                        std::move(Ctx), std::move(QueueCtx), Update,
+                        Invalidation, std::move(Invalidate)});
   }
   RequestsCV.notify_all();
 }
@@ -1071,13 +1098,16 @@
       // Requests.front(), so prefer them first to preserve LSP order.
       if (!PreambleRequests.empty()) {
         CurrentRequest = std::move(PreambleRequests.front());
-        PreambleRequests.pop();
+        PreambleRequests.pop_front();
       } else {
         CurrentRequest = std::move(Requests.front());
         Requests.pop_front();
       }
     } // unlock Mutex
 
+    // Inform tracing that the request was dequeued.
+    CurrentRequest->QueueCtx.reset();
+
     // It is safe to perform reads to CurrentRequest without holding the lock as
     // only writer is also this thread.
     {


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