https://github.com/jansvoboda11 created
https://github.com/llvm/llvm-project/pull/108056
Clang's `-cc1 -print-stats` shows lots of useful internal data including basic
`FileManager` stats. Since this layer caches some results, it is unclear how
that information translates to actual filesystem accesses. This PR uses
`llvm::vfs::TracingFileSystem` to provide that missing information.
Similar mechanism is implemented for `clang-scan-deps`'s verbose mode (`-v`).
IO contention proved to be a real bottleneck a couple of times already and this
new feature should make those easier to detect in the future. The tracing VFS
is inserted below the caching FS and above the real FS.
>From 9b9d8f02e26839758c51c7e48c1ba43dc3c24146 Mon Sep 17 00:00:00 2001
From: Jan Svoboda <jan_svob...@apple.com>
Date: Tue, 10 Sep 2024 09:55:07 -0700
Subject: [PATCH] [clang][deps] Print tracing VFS data
---
.../DependencyScanningService.h | 6 +++-
.../DependencyScanningTool.h | 2 ++
.../DependencyScanningWorker.h | 2 ++
clang/lib/Basic/FileManager.cpp | 11 +++++++
clang/lib/Frontend/CompilerInstance.cpp | 3 ++
.../DependencyScanningService.cpp | 4 +--
.../DependencyScanningWorker.cpp | 3 ++
clang/test/ClangScanDeps/verbose.test | 28 +++++++++++++++++
clang/test/Misc/print-stats-vfs.test | 17 +++++++++++
clang/tools/clang-scan-deps/ClangScanDeps.cpp | 30 ++++++++++++++++++-
10 files changed, 102 insertions(+), 4 deletions(-)
create mode 100644 clang/test/ClangScanDeps/verbose.test
create mode 100644 clang/test/Misc/print-stats-vfs.test
diff --git
a/clang/include/clang/Tooling/DependencyScanning/DependencyScanningService.h
b/clang/include/clang/Tooling/DependencyScanning/DependencyScanningService.h
index 557f0e547ab4a8..4a343f2872d8d9 100644
--- a/clang/include/clang/Tooling/DependencyScanning/DependencyScanningService.h
+++ b/clang/include/clang/Tooling/DependencyScanning/DependencyScanningService.h
@@ -76,7 +76,7 @@ class DependencyScanningService {
DependencyScanningService(
ScanningMode Mode, ScanningOutputFormat Format,
ScanningOptimizations OptimizeArgs = ScanningOptimizations::Default,
- bool EagerLoadModules = false);
+ bool EagerLoadModules = false, bool TraceVFS = false);
ScanningMode getMode() const { return Mode; }
@@ -86,6 +86,8 @@ class DependencyScanningService {
bool shouldEagerLoadModules() const { return EagerLoadModules; }
+ bool shouldTraceVFS() const { return TraceVFS; }
+
DependencyScanningFilesystemSharedCache &getSharedCache() {
return SharedCache;
}
@@ -97,6 +99,8 @@ class DependencyScanningService {
const ScanningOptimizations OptimizeArgs;
/// Whether to set up command-lines to load PCM files eagerly.
const bool EagerLoadModules;
+ /// Whether to trace VFS accesses.
+ const bool TraceVFS;
/// The global file system cache.
DependencyScanningFilesystemSharedCache SharedCache;
};
diff --git
a/clang/include/clang/Tooling/DependencyScanning/DependencyScanningTool.h
b/clang/include/clang/Tooling/DependencyScanning/DependencyScanningTool.h
index cb9476d1550df3..012237e0278f4a 100644
--- a/clang/include/clang/Tooling/DependencyScanning/DependencyScanningTool.h
+++ b/clang/include/clang/Tooling/DependencyScanning/DependencyScanningTool.h
@@ -144,6 +144,8 @@ class DependencyScanningTool {
StringRef CWD, const llvm::DenseSet<ModuleID> &AlreadySeen,
LookupModuleOutputCallback LookupModuleOutput);
+ llvm::vfs::FileSystem &getWorkerVFS() const { return Worker.getVFS(); }
+
private:
DependencyScanningWorker Worker;
};
diff --git
a/clang/include/clang/Tooling/DependencyScanning/DependencyScanningWorker.h
b/clang/include/clang/Tooling/DependencyScanning/DependencyScanningWorker.h
index 0f607862194b31..da6e0401411a34 100644
--- a/clang/include/clang/Tooling/DependencyScanning/DependencyScanningWorker.h
+++ b/clang/include/clang/Tooling/DependencyScanning/DependencyScanningWorker.h
@@ -104,6 +104,8 @@ class DependencyScanningWorker {
bool shouldEagerLoadModules() const { return EagerLoadModules; }
+ llvm::vfs::FileSystem &getVFS() const { return *BaseFS; }
+
private:
std::shared_ptr<PCHContainerOperations> PCHContainerOps;
/// The file system to be used during the scan.
diff --git a/clang/lib/Basic/FileManager.cpp b/clang/lib/Basic/FileManager.cpp
index 4509cee1ca0fed..6097b85a03064b 100644
--- a/clang/lib/Basic/FileManager.cpp
+++ b/clang/lib/Basic/FileManager.cpp
@@ -692,5 +692,16 @@ void FileManager::PrintStats() const {
llvm::errs() << NumFileLookups << " file lookups, "
<< NumFileCacheMisses << " file cache misses.\n";
+ getVirtualFileSystem().visit([](llvm::vfs::FileSystem &VFS) {
+ if (auto *T = dyn_cast_or_null<llvm::vfs::TracingFileSystem>(&VFS))
+ llvm::errs() << "\n*** Virtual File System Stats:\n"
+ << T->NumStatusCalls << " status() calls\n"
+ << T->NumOpenFileForReadCalls << " openFileForRead()
calls\n"
+ << T->NumDirBeginCalls << " dir_begin() calls\n"
+ << T->NumGetRealPathCalls << " getRealPath() calls\n"
+ << T->NumExistsCalls << " exists() calls\n"
+ << T->NumIsLocalCalls << " isLocal() calls\n";
+ });
+
//llvm::errs() << PagesMapped << BytesOfPagesMapped << FSLookups;
}
diff --git a/clang/lib/Frontend/CompilerInstance.cpp
b/clang/lib/Frontend/CompilerInstance.cpp
index 1364641a9b71e1..5a273474f1d6b6 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -381,6 +381,9 @@ FileManager *CompilerInstance::createFileManager(
: createVFSFromCompilerInvocation(getInvocation(),
getDiagnostics());
assert(VFS && "FileManager has no VFS?");
+ if (getFrontendOpts().ShowStats)
+ VFS =
+
llvm::makeIntrusiveRefCnt<llvm::vfs::TracingFileSystem>(std::move(VFS));
FileMgr = new FileManager(getFileSystemOpts(), std::move(VFS));
return FileMgr.get();
}
diff --git a/clang/lib/Tooling/DependencyScanning/DependencyScanningService.cpp
b/clang/lib/Tooling/DependencyScanning/DependencyScanningService.cpp
index 7458ef484b16c4..4fb5977580497c 100644
--- a/clang/lib/Tooling/DependencyScanning/DependencyScanningService.cpp
+++ b/clang/lib/Tooling/DependencyScanning/DependencyScanningService.cpp
@@ -15,9 +15,9 @@ using namespace dependencies;
DependencyScanningService::DependencyScanningService(
ScanningMode Mode, ScanningOutputFormat Format,
- ScanningOptimizations OptimizeArgs, bool EagerLoadModules)
+ ScanningOptimizations OptimizeArgs, bool EagerLoadModules, bool TraceVFS)
: Mode(Mode), Format(Format), OptimizeArgs(OptimizeArgs),
- EagerLoadModules(EagerLoadModules) {
+ EagerLoadModules(EagerLoadModules), TraceVFS(TraceVFS) {
// Initialize targets for object file support.
llvm::InitializeAllTargets();
llvm::InitializeAllTargetMCs();
diff --git a/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
b/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
index 09ad5ebc7954cf..d77187bfb1f2b8 100644
--- a/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
+++ b/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
@@ -501,6 +501,9 @@ DependencyScanningWorker::DependencyScanningWorker(
// The scanner itself writes only raw ast files.
PCHContainerOps->registerWriter(std::make_unique<RawPCHContainerWriter>());
+ if (Service.shouldTraceVFS())
+ FS =
llvm::makeIntrusiveRefCnt<llvm::vfs::TracingFileSystem>(std::move(FS));
+
switch (Service.getMode()) {
case ScanningMode::DependencyDirectivesScan:
DepFS =
diff --git a/clang/test/ClangScanDeps/verbose.test
b/clang/test/ClangScanDeps/verbose.test
new file mode 100644
index 00000000000000..99c5214c762018
--- /dev/null
+++ b/clang/test/ClangScanDeps/verbose.test
@@ -0,0 +1,28 @@
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+// RUN: sed -e "s|DIR|%/t|g" %t/cdb.json.in > %t/cdb.json
+
+// RUN: clang-scan-deps -compilation-database %t/cdb.json -v -o %t/result.json
2>&1 | FileCheck %s
+// CHECK: *** Virtual File System Stats:
+// CHECK-NEXT: {{[[:digit:]]+}} status() calls
+// CHECK-NEXT: {{[[:digit:]]+}} openFileForRead() calls
+// CHECK-NEXT: {{[[:digit:]]+}} dir_begin() calls
+// CHECK-NEXT: {{[[:digit:]]+}} getRealPath() calls
+// CHECK-NEXT: {{[[:digit:]]+}} exists() calls
+// CHECK-NEXT: {{[[:digit:]]+}} isLocal() calls
+
+//--- tu.c
+
+//--- cdb.json.in
+[
+ {
+ "file": "DIR/tu.c"
+ "directory": "DIR",
+ "command": "clang -c DIR/tu.c -o DIR/tu.o"
+ },
+ {
+ "file": "DIR/tu.c"
+ "directory": "DIR",
+ "command": "clang -c DIR/tu.c -o DIR/tu.o"
+ }
+]
diff --git a/clang/test/Misc/print-stats-vfs.test
b/clang/test/Misc/print-stats-vfs.test
new file mode 100644
index 00000000000000..65446cb7a5077d
--- /dev/null
+++ b/clang/test/Misc/print-stats-vfs.test
@@ -0,0 +1,17 @@
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+
+// RUN: %clang_cc1 -fsyntax-only %t/tu.c -I %t/dir1 -I %t/dir2 -print-stats
2>&1 | FileCheck %s
+
+//--- tu.c
+#include "header.h"
+//--- dir1/other.h
+//--- dir2/header.h
+
+// CHECK: *** Virtual File System Stats:
+// CHECK-NEXT: {{[[:digit:]]+}} status() calls
+// CHECK-NEXT: {{[[:digit:]]+}} openFileForRead() calls
+// CHECK-NEXT: {{[[:digit:]]+}} dir_begin() calls
+// CHECK-NEXT: {{[[:digit:]]+}} getRealPath() calls
+// CHECK-NEXT: {{[[:digit:]]+}} exists() calls
+// CHECK-NEXT: {{[[:digit:]]+}} isLocal() calls
diff --git a/clang/tools/clang-scan-deps/ClangScanDeps.cpp
b/clang/tools/clang-scan-deps/ClangScanDeps.cpp
index a8f6150dd3493d..bf1621c91c2c92 100644
--- a/clang/tools/clang-scan-deps/ClangScanDeps.cpp
+++ b/clang/tools/clang-scan-deps/ClangScanDeps.cpp
@@ -915,6 +915,13 @@ int clang_scan_deps_main(int argc, char **argv, const
llvm::ToolContext &) {
if (Format == ScanningOutputFormat::Full)
FD.emplace(ModuleName.empty() ? Inputs.size() : 0);
+ std::atomic<size_t> NumStatusCalls = 0;
+ std::atomic<size_t> NumOpenFileForReadCalls = 0;
+ std::atomic<size_t> NumDirBeginCalls = 0;
+ std::atomic<size_t> NumGetRealPathCalls = 0;
+ std::atomic<size_t> NumExistsCalls = 0;
+ std::atomic<size_t> NumIsLocalCalls = 0;
+
auto ScanningTask = [&](DependencyScanningService &Service) {
DependencyScanningTool WorkerTool(Service);
@@ -999,10 +1006,21 @@ int clang_scan_deps_main(int argc, char **argv, const
llvm::ToolContext &) {
HadErrors = true;
}
}
+
+ WorkerTool.getWorkerVFS().visit([&](llvm::vfs::FileSystem &VFS) {
+ if (auto *T = dyn_cast_or_null<llvm::vfs::TracingFileSystem>(&VFS)) {
+ NumStatusCalls += T->NumStatusCalls;
+ NumOpenFileForReadCalls += T->NumOpenFileForReadCalls;
+ NumDirBeginCalls += T->NumDirBeginCalls;
+ NumGetRealPathCalls += T->NumGetRealPathCalls;
+ NumExistsCalls += T->NumExistsCalls;
+ NumIsLocalCalls += T->NumIsLocalCalls;
+ }
+ });
};
DependencyScanningService Service(ScanMode, Format, OptimizeArgs,
- EagerLoadModules);
+ EagerLoadModules, /*TraceVFS=*/Verbose);
llvm::Timer T;
T.startTimer();
@@ -1024,6 +1042,16 @@ int clang_scan_deps_main(int argc, char **argv, const
llvm::ToolContext &) {
Pool.wait();
}
+ if (Verbose) {
+ llvm::errs() << "\n*** Virtual File System Stats:\n"
+ << NumStatusCalls << " status() calls\n"
+ << NumOpenFileForReadCalls << " openFileForRead() calls\n"
+ << NumDirBeginCalls << " dir_begin() calls\n"
+ << NumGetRealPathCalls << " getRealPath() calls\n"
+ << NumExistsCalls << " exists() calls\n"
+ << NumIsLocalCalls << " isLocal() calls\n";
+ }
+
T.stopTimer();
if (PrintTiming)
llvm::errs() << llvm::format(
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