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[clangd] Run PreambleThread in async mode behind a flag 

Summary: Depends on D80198.

This patch implies ASTs might be built with stale preambles without
blocking for a fresh one. It also drops any guarantees on every preamble
version being built. In case of multiple preamble build requests, in
addition to being debounced.

Any preamble requested with a WantDiags::Yes will always be built, this
is ensured by blocking enqueueing of any subsequent reqest.

AST worker will still block for initial preamble to reduce duplicate
work.

Subscribers: ilya-biryukov, javed.absar, MaskRay, jkorous, arphaman, jfb, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D80293
This commit is contained in:
Kadir Cetinkaya 2020-04-07 21:18:00 +02:00
parent 92f3d29af0
commit 1f4ba66ecc
No known key found for this signature in database
GPG Key ID: E39E36B8D2057ED6
9 changed files with 174 additions and 48 deletions
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2
clang-tools-extra/clangd/ClangdServer.cpp
View File

@ -114,6 +114,7 @@ ClangdServer::Options ClangdServer::optsForTest() {
Opts.StorePreamblesInMemory = true;
Opts.AsyncThreadsCount = 4; // Consistent!
Opts.TheiaSemanticHighlighting = true;
Opts.AsyncPreambleBuilds = true;
return Opts;
}
@ -123,6 +124,7 @@ ClangdServer::Options::operator TUScheduler::Options() const {
Opts.RetentionPolicy = RetentionPolicy;
Opts.StorePreamblesInMemory = StorePreamblesInMemory;
Opts.UpdateDebounce = UpdateDebounce;
Opts.AsyncPreambleBuilds = AsyncPreambleBuilds;
return Opts;
}

3
clang-tools-extra/clangd/ClangdServer.h
View File

@ -97,6 +97,9 @@ public:
/// Cached preambles are potentially large. If false, store them on disk.
bool StorePreamblesInMemory = true;
/// Reuse even stale preambles, and rebuild them in the background.
/// This improves latency at the cost of accuracy.
bool AsyncPreambleBuilds = false;
/// If true, ClangdServer builds a dynamic in-memory index for symbols in
/// opened files and uses the index to augment code completion results.

5
clang-tools-extra/clangd/ParsedAST.cpp
View File

@ -551,5 +551,10 @@ ParsedAST::ParsedAST(llvm::StringRef Version,
assert(this->Action);
}
llvm::Optional<llvm::StringRef> ParsedAST::preambleVersion() const {
if (!Preamble)
return llvm::None;
return llvm::StringRef(Preamble->Version);
}
} // namespace clangd
} // namespace clang

7
clang-tools-extra/clangd/ParsedAST.h
View File

@ -33,6 +33,9 @@
#include "clang/Tooling/CompilationDatabase.h"
#include "clang/Tooling/Syntax/Tokens.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/StringRef.h"
#include <memory>
#include <string>
#include <vector>
@ -102,6 +105,10 @@ public:
/// Returns the version of the ParseInputs this AST was built from.
llvm::StringRef version() const { return Version; }
/// Returns the version of the ParseInputs used to build Preamble part of this
/// AST. Might be None if no Preamble is used.
llvm::Optional<llvm::StringRef> preambleVersion() const;
private:
ParsedAST(llvm::StringRef Version,
std::shared_ptr<const PreambleData> Preamble,

99
clang-tools-extra/clangd/TUScheduler.cpp
View File

@ -239,10 +239,14 @@ public:
return;
}
{
std::lock_guard<std::mutex> Lock(Mutex);
// If shutdown is issued, don't bother building.
if (Done)
return;
std::unique_lock<std::mutex> Lock(Mutex);
// If NextReq was requested with WantDiagnostics::Yes we cannot just drop
// that on the floor. Block until we start building it. This won't
// dead-lock as we are blocking the caller thread, while builds continue
// on preamble thread.
ReqCV.wait(Lock, [this] {
return !NextReq || NextReq->WantDiags != WantDiagnostics::Yes;
});
NextReq = std::move(Req);
}
// Let the worker thread know there's a request, notify_one is safe as there
@ -359,8 +363,7 @@ class ASTWorker {
friend class ASTWorkerHandle;
ASTWorker(PathRef FileName, const GlobalCompilationDatabase &CDB,
TUScheduler::ASTCache &LRUCache, Semaphore &Barrier, bool RunSync,
DebouncePolicy UpdateDebounce, bool StorePreamblesInMemory,
ParsingCallbacks &Callbacks);
const TUScheduler::Options &Opts, ParsingCallbacks &Callbacks);
public:
/// Create a new ASTWorker and return a handle to it.
@ -368,11 +371,12 @@ public:
/// is null, all requests will be processed on the calling thread
/// synchronously instead. \p Barrier is acquired when processing each
/// request, it is used to limit the number of actively running threads.
static ASTWorkerHandle
create(PathRef FileName, const GlobalCompilationDatabase &CDB,
TUScheduler::ASTCache &IdleASTs, AsyncTaskRunner *Tasks,
Semaphore &Barrier, DebouncePolicy UpdateDebounce,
bool StorePreamblesInMemory, ParsingCallbacks &Callbacks);
static ASTWorkerHandle create(PathRef FileName,
const GlobalCompilationDatabase &CDB,
TUScheduler::ASTCache &IdleASTs,
AsyncTaskRunner *Tasks, Semaphore &Barrier,
const TUScheduler::Options &Opts,
ParsingCallbacks &Callbacks);
~ASTWorker();
void update(ParseInputs Inputs, WantDiagnostics);
@ -476,6 +480,7 @@ private:
std::queue<Request> PreambleRequests; /* GUARDED_BY(Mutex) */
llvm::Optional<Request> CurrentRequest; /* GUARDED_BY(Mutex) */
mutable std::condition_variable RequestsCV;
Notification ReceivedPreamble;
/// Guards the callback that publishes results of AST-related computations
/// (diagnostics, highlightings) and file statuses.
std::mutex PublishMu;
@ -535,14 +540,14 @@ private:
std::shared_ptr<ASTWorker> Worker;
};
ASTWorkerHandle
ASTWorker::create(PathRef FileName, const GlobalCompilationDatabase &CDB,
TUScheduler::ASTCache &IdleASTs, AsyncTaskRunner *Tasks,
Semaphore &Barrier, DebouncePolicy UpdateDebounce,
bool StorePreamblesInMemory, ParsingCallbacks &Callbacks) {
std::shared_ptr<ASTWorker> Worker(
new ASTWorker(FileName, CDB, IdleASTs, Barrier, /*RunSync=*/!Tasks,
UpdateDebounce, StorePreamblesInMemory, Callbacks));
ASTWorkerHandle ASTWorker::create(PathRef FileName,
const GlobalCompilationDatabase &CDB,
TUScheduler::ASTCache &IdleASTs,
AsyncTaskRunner *Tasks, Semaphore &Barrier,
const TUScheduler::Options &Opts,
ParsingCallbacks &Callbacks) {
std::shared_ptr<ASTWorker> Worker(new ASTWorker(
FileName, CDB, IdleASTs, Barrier, /*RunSync=*/!Tasks, Opts, Callbacks));
if (Tasks) {
Tasks->runAsync("ASTWorker:" + llvm::sys::path::filename(FileName),
[Worker]() { Worker->run(); });
@ -555,15 +560,13 @@ ASTWorker::create(PathRef FileName, const GlobalCompilationDatabase &CDB,
ASTWorker::ASTWorker(PathRef FileName, const GlobalCompilationDatabase &CDB,
TUScheduler::ASTCache &LRUCache, Semaphore &Barrier,
bool RunSync, DebouncePolicy UpdateDebounce,
bool StorePreamblesInMemory, ParsingCallbacks &Callbacks)
: IdleASTs(LRUCache), RunSync(RunSync), UpdateDebounce(UpdateDebounce),
bool RunSync, const TUScheduler::Options &Opts,
ParsingCallbacks &Callbacks)
: IdleASTs(LRUCache), RunSync(RunSync), UpdateDebounce(Opts.UpdateDebounce),
FileName(FileName), CDB(CDB), Callbacks(Callbacks), Barrier(Barrier),
Done(false), Status(FileName, Callbacks),
PreamblePeer(FileName, Callbacks, StorePreamblesInMemory,
// FIXME: Run PreamblePeer asynchronously once ast patching
// is available.
/*RunSync=*/true, Status, *this) {
PreamblePeer(FileName, Callbacks, Opts.StorePreamblesInMemory,
RunSync || !Opts.AsyncPreambleBuilds, Status, *this) {
// Set a fallback command because compile command can be accessed before
// `Inputs` is initialized. Other fields are only used after initialization
// from client inputs.
@ -648,6 +651,12 @@ void ASTWorker::update(ParseInputs Inputs, WantDiagnostics WantDiags) {
PreamblePeer.update(std::move(Invocation), std::move(Inputs),
std::move(CompilerInvocationDiags), WantDiags);
// Block until first preamble is ready, as patching an empty preamble would
// imply rebuilding it from scratch.
// This isn't the natural place to block, rather where the preamble would be
// consumed. But that's too late, we'd be running on the worker thread with
// the PreambleTask scheduled and so we'd deadlock.
ReceivedPreamble.wait();
return;
};
startTask(TaskName, std::move(Task), WantDiags, TUScheduler::NoInvalidation);
@ -771,6 +780,7 @@ void ASTWorker::updatePreamble(std::unique_ptr<CompilerInvocation> CI,
};
if (RunSync) {
Task();
ReceivedPreamble.notify();
return;
}
{
@ -779,6 +789,7 @@ void ASTWorker::updatePreamble(std::unique_ptr<CompilerInvocation> CI,
steady_clock::now(), Context::current().clone(),
llvm::None, TUScheduler::NoInvalidation, nullptr});
}
ReceivedPreamble.notify();
RequestsCV.notify_all();
}
@ -915,6 +926,7 @@ void ASTWorker::stop() {
Done = true;
}
// We are no longer going to build any preambles, let the waiters know that.
ReceivedPreamble.notify();
BuiltFirstPreamble.notify();
PreamblePeer.stop();
Status.stop();
@ -1117,10 +1129,24 @@ bool ASTWorker::shouldSkipHeadLocked() const {
}
bool ASTWorker::blockUntilIdle(Deadline Timeout) const {
std::unique_lock<std::mutex> Lock(Mutex);
return wait(Lock, RequestsCV, Timeout, [&] {
return PreambleRequests.empty() && Requests.empty() && !CurrentRequest;
});
auto WaitUntilASTWorkerIsIdle = [&] {
std::unique_lock<std::mutex> Lock(Mutex);
return wait(Lock, RequestsCV, Timeout, [&] {
return PreambleRequests.empty() && Requests.empty() && !CurrentRequest;
});
};
// Make sure ASTWorker has processed all requests, which might issue new
// updates to PreamblePeer.
WaitUntilASTWorkerIsIdle();
// Now that ASTWorker processed all requests, ensure PreamblePeer has served
// all update requests. This might create new PreambleRequests for the
// ASTWorker.
PreamblePeer.blockUntilIdle(Timeout);
assert(Requests.empty() &&
"No new normal tasks can be scheduled concurrently with "
"blockUntilIdle(): ASTWorker isn't threadsafe");
// Finally make sure ASTWorker has processed all of the preamble updates.
return WaitUntilASTWorkerIsIdle();
}
// Render a TUAction to a user-facing string representation.
@ -1178,13 +1204,12 @@ struct TUScheduler::FileData {
TUScheduler::TUScheduler(const GlobalCompilationDatabase &CDB,
const Options &Opts,
std::unique_ptr<ParsingCallbacks> Callbacks)
: CDB(CDB), StorePreamblesInMemory(Opts.StorePreamblesInMemory),
: CDB(CDB), Opts(Opts),
Callbacks(Callbacks ? move(Callbacks)
: std::make_unique<ParsingCallbacks>()),
Barrier(Opts.AsyncThreadsCount),
IdleASTs(
std::make_unique<ASTCache>(Opts.RetentionPolicy.MaxRetainedASTs)),
UpdateDebounce(Opts.UpdateDebounce) {
std::make_unique<ASTCache>(Opts.RetentionPolicy.MaxRetainedASTs)) {
if (0 < Opts.AsyncThreadsCount) {
PreambleTasks.emplace();
WorkerThreads.emplace();
@ -1218,10 +1243,10 @@ bool TUScheduler::update(PathRef File, ParseInputs Inputs,
bool NewFile = FD == nullptr;
if (!FD) {
// Create a new worker to process the AST-related tasks.
ASTWorkerHandle Worker = ASTWorker::create(
File, CDB, *IdleASTs,
WorkerThreads ? WorkerThreads.getPointer() : nullptr, Barrier,
UpdateDebounce, StorePreamblesInMemory, *Callbacks);
ASTWorkerHandle Worker =
ASTWorker::create(File, CDB, *IdleASTs,
WorkerThreads ? WorkerThreads.getPointer() : nullptr,
Barrier, Opts, *Callbacks);
FD = std::unique_ptr<FileData>(
new FileData{Inputs.Contents, std::move(Worker)});
} else {

7
clang-tools-extra/clangd/TUScheduler.h
View File

@ -191,6 +191,10 @@ public:
/// Determines when to keep idle ASTs in memory for future use.
ASTRetentionPolicy RetentionPolicy;
/// Whether to run PreamblePeer asynchronously.
/// No-op if AsyncThreadsCount is 0.
bool AsyncPreambleBuilds = false;
};
TUScheduler(const GlobalCompilationDatabase &CDB, const Options &Opts,
@ -301,7 +305,7 @@ public:
private:
const GlobalCompilationDatabase &CDB;
const bool StorePreamblesInMemory;
const Options Opts;
std::unique_ptr<ParsingCallbacks> Callbacks; // not nullptr
Semaphore Barrier;
llvm::StringMap<std::unique_ptr<FileData>> Files;
@ -310,7 +314,6 @@ private:
// asynchronously.
llvm::Optional<AsyncTaskRunner> PreambleTasks;
llvm::Optional<AsyncTaskRunner> WorkerThreads;
DebouncePolicy UpdateDebounce;
};
} // namespace clangd

9
clang-tools-extra/clangd/tool/ClangdMain.cpp
View File

@ -417,6 +417,15 @@ opt<bool> PrettyPrint{
init(false),
};
opt<bool> AsyncPreamble{
"async-preamble",
cat(Misc),
desc("Reuse even stale preambles, and rebuild them in the background. This "
"improves latency at the cost of accuracy."),
init(ClangdServer::Options().AsyncPreambleBuilds),
Hidden,
};
/// Supports a test URI scheme with relaxed constraints for lit tests.
/// The path in a test URI will be combined with a platform-specific fake
/// directory to form an absolute path. For example, test:///a.cpp is resolved

12
clang-tools-extra/clangd/unittests/ClangdTests.cpp
View File

@ -211,18 +211,18 @@ int b = a;
FS.Files[FooCpp] = SourceContents;
Server.addDocument(FooCpp, SourceContents);
auto DumpParse1 = dumpASTWithoutMemoryLocs(Server, FooCpp);
ASSERT_TRUE(Server.blockUntilIdleForTest()) << "Waiting for diagnostics";
auto DumpParse1 = dumpASTWithoutMemoryLocs(Server, FooCpp);
EXPECT_FALSE(DiagConsumer.hadErrorInLastDiags());
Server.addDocument(FooCpp, "");
auto DumpParseEmpty = dumpASTWithoutMemoryLocs(Server, FooCpp);
ASSERT_TRUE(Server.blockUntilIdleForTest()) << "Waiting for diagnostics";
auto DumpParseEmpty = dumpASTWithoutMemoryLocs(Server, FooCpp);
EXPECT_FALSE(DiagConsumer.hadErrorInLastDiags());
Server.addDocument(FooCpp, SourceContents);
auto DumpParse2 = dumpASTWithoutMemoryLocs(Server, FooCpp);
ASSERT_TRUE(Server.blockUntilIdleForTest()) << "Waiting for diagnostics";
auto DumpParse2 = dumpASTWithoutMemoryLocs(Server, FooCpp);
EXPECT_FALSE(DiagConsumer.hadErrorInLastDiags());
EXPECT_EQ(DumpParse1, DumpParse2);
@ -247,20 +247,20 @@ int b = a;
FS.Files[FooCpp] = SourceContents;
Server.addDocument(FooCpp, SourceContents);
auto DumpParse1 = dumpASTWithoutMemoryLocs(Server, FooCpp);
ASSERT_TRUE(Server.blockUntilIdleForTest()) << "Waiting for diagnostics";
auto DumpParse1 = dumpASTWithoutMemoryLocs(Server, FooCpp);
EXPECT_FALSE(DiagConsumer.hadErrorInLastDiags());
FS.Files[FooH] = "";
Server.addDocument(FooCpp, SourceContents);
auto DumpParseDifferent = dumpASTWithoutMemoryLocs(Server, FooCpp);
ASSERT_TRUE(Server.blockUntilIdleForTest()) << "Waiting for diagnostics";
auto DumpParseDifferent = dumpASTWithoutMemoryLocs(Server, FooCpp);
EXPECT_TRUE(DiagConsumer.hadErrorInLastDiags());
FS.Files[FooH] = "int a;";
Server.addDocument(FooCpp, SourceContents);
auto DumpParse2 = dumpASTWithoutMemoryLocs(Server, FooCpp);
ASSERT_TRUE(Server.blockUntilIdleForTest()) << "Waiting for diagnostics";
auto DumpParse2 = dumpASTWithoutMemoryLocs(Server, FooCpp);
EXPECT_FALSE(DiagConsumer.hadErrorInLastDiags());
EXPECT_EQ(DumpParse1, DumpParse2);

78
clang-tools-extra/clangd/unittests/TUSchedulerTests.cpp
View File

@ -21,14 +21,20 @@
#include "support/Threading.h"
#include "clang/Basic/DiagnosticDriver.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/FunctionExtras.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/ScopeExit.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringRef.h"
#include "gmock/gmock.h"
#include "gtest/gtest.h"
#include <algorithm>
#include <atomic>
#include <chrono>
#include <cstdint>
#include <memory>
#include <string>
#include <utility>
namespace clang {
@ -407,6 +413,7 @@ TEST_F(TUSchedulerTests, ManyUpdates) {
int TotalASTReads = 0;
int TotalPreambleReads = 0;
int TotalUpdates = 0;
llvm::StringMap<int> LatestDiagVersion;
// Run TUScheduler and collect some stats.
{
@ -441,15 +448,23 @@ TEST_F(TUSchedulerTests, ManyUpdates) {
auto Inputs = getInputs(File, Contents.str());
{
WithContextValue WithNonce(NonceKey, ++Nonce);
Inputs.Version = std::to_string(Nonce);
Inputs.Version = std::to_string(UpdateI);
updateWithDiags(
S, File, Inputs, WantDiagnostics::Auto,
[File, Nonce, &Mut, &TotalUpdates](std::vector<Diag>) {
[File, Nonce, Version(Inputs.Version), &Mut, &TotalUpdates,
&LatestDiagVersion](std::vector<Diag>) {
EXPECT_THAT(Context::current().get(NonceKey), Pointee(Nonce));
std::lock_guard<std::mutex> Lock(Mut);
++TotalUpdates;
EXPECT_EQ(File, *TUScheduler::getFileBeingProcessedInContext());
// Make sure Diags are for a newer version.
auto It = LatestDiagVersion.try_emplace(File, -1);
const int PrevVersion = It.first->second;
int CurVersion;
ASSERT_TRUE(llvm::to_integer(Version, CurVersion, 10));
EXPECT_LT(PrevVersion, CurVersion);
It.first->getValue() = CurVersion;
});
}
{
@ -494,7 +509,13 @@ TEST_F(TUSchedulerTests, ManyUpdates) {
} // TUScheduler destructor waits for all operations to finish.
std::lock_guard<std::mutex> Lock(Mut);
EXPECT_EQ(TotalUpdates, FilesCount * UpdatesPerFile);
// Updates might get coalesced in preamble thread and result in dropping
// diagnostics for intermediate snapshots.
EXPECT_GE(TotalUpdates, FilesCount);
EXPECT_LE(TotalUpdates, FilesCount * UpdatesPerFile);
// We should receive diags for last update.
for (const auto &Entry : LatestDiagVersion)
EXPECT_EQ(Entry.second, UpdatesPerFile - 1);
EXPECT_EQ(TotalASTReads, FilesCount * UpdatesPerFile);
EXPECT_EQ(TotalPreambleReads, FilesCount * UpdatesPerFile);
}
@ -972,6 +993,57 @@ TEST(DebouncePolicy, Compute) {
EXPECT_NEAR(25, Compute({}), 0.01) << "no history -> max";
}
TEST_F(TUSchedulerTests, AsyncPreambleThread) {
// Blocks preamble thread while building preamble with \p BlockVersion until
// \p N is notified.
class BlockPreambleThread : public ParsingCallbacks {
public:
BlockPreambleThread(llvm::StringRef BlockVersion, Notification &N)
: BlockVersion(BlockVersion), N(N) {}
void onPreambleAST(PathRef Path, llvm::StringRef Version, ASTContext &Ctx,
std::shared_ptr<clang::Preprocessor> PP,
const CanonicalIncludes &) override {
if (Version == BlockVersion)
N.wait();
}
private:
llvm::StringRef BlockVersion;
Notification &N;
};
static constexpr llvm::StringLiteral InputsV0 = "v0";
static constexpr llvm::StringLiteral InputsV1 = "v1";
Notification Ready;
TUScheduler S(CDB, optsForTest(),
std::make_unique<BlockPreambleThread>(InputsV1, Ready));
Path File = testPath("foo.cpp");
auto PI = getInputs(File, "");
PI.Version = InputsV0.str();
S.update(File, PI, WantDiagnostics::Auto);
S.blockUntilIdle(timeoutSeconds(10));
// Block preamble builds.
PI.Version = InputsV1.str();
// Issue second update which will block preamble thread.
S.update(File, PI, WantDiagnostics::Auto);
Notification RunASTAction;
// Issue an AST read, which shouldn't be blocked and see latest version of the
// file.
S.runWithAST("test", File, [&](Expected<InputsAndAST> AST) {
ASSERT_TRUE(bool(AST));
// Make sure preamble is built with stale inputs, but AST was built using
// new ones.
EXPECT_THAT(AST->AST.preambleVersion(), InputsV0);
EXPECT_THAT(AST->Inputs.Version, InputsV1.str());
RunASTAction.notify();
});
RunASTAction.wait();
Ready.notify();
}
} // namespace
} // namespace clangd
} // namespace clang