[scudo] Add ConditionVariable in SizeClassAllocator64 (#69031)

This may improve the waiting of `Region->MMLock` while trying to refill
the freelist. Instead of always waiting on the completion of
`populateFreeListAndPopBatch()` or `releaseToOSMaybe()`, `pushBlocks()`
also refills the freelist. This increases the chance of earlier return
from `popBatches()`.

The support of condition variable hasn't been done for all platforms.
Therefore, add another `popBatchWithCV()` and it can be configured in
the allocator configuration by setting `Primary::UseConditionVariable`
and the desired `ConditionVariableT`.

Reviewed By: cferris

Differential Revision: https://reviews.llvm.org/D156146

Author: ChiaHungDuan

compiler-rt/lib/scudo/standalone/CMakeLists.txt

@@ -62,6 +62,9 @@ set(SCUDO_HEADERS
   bytemap.h
   checksum.h
   chunk.h
+  condition_variable.h
+  condition_variable_base.h
+  condition_variable_linux.h
   combined.h
   common.h
   flags_parser.h
@@ -104,6 +107,7 @@ set(SCUDO_HEADERS
 set(SCUDO_SOURCES
   checksum.cpp
   common.cpp
+  condition_variable_linux.cpp
   crc32_hw.cpp
   flags_parser.cpp
   flags.cpp

compiler-rt/lib/scudo/standalone/allocator_config.h

@@ -11,6 +11,7 @@
 
 #include "combined.h"
 #include "common.h"
+#include "condition_variable.h"
 #include "flags.h"
 #include "primary32.h"
 #include "primary64.h"
@@ -82,6 +83,14 @@ namespace scudo {
 //     // Defines the minimal & maximal release interval that can be set.
 //     static const s32 MinReleaseToOsIntervalMs = INT32_MIN;
 //     static const s32 MaxReleaseToOsIntervalMs = INT32_MAX;
+//
+//     // Use condition variable to shorten the waiting time of refillment of
+//     // freelist. Note that this depends on the implementation of condition
+//     // variable on each platform and the performance may vary so that it
+//     // doesn't guarantee a performance benefit.
+//     // Note that both variables have to be defined to enable it.
+//     static const bool UseConditionVariable = true;
+//     using ConditionVariableT = ConditionVariableLinux;
 //   };
 //   // Defines the type of Primary allocator to use.
 //   template <typename Config> using PrimaryT = SizeClassAllocator64<Config>;

compiler-rt/lib/scudo/standalone/condition_variable.h

@@ -0,0 +1,60 @@
+//===-- condition_variable.h ------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SCUDO_CONDITION_VARIABLE_H_
+#define SCUDO_CONDITION_VARIABLE_H_
+
+#include "condition_variable_base.h"
+
+#include "common.h"
+#include "platform.h"
+
+#include "condition_variable_linux.h"
+
+namespace scudo {
+
+// A default implementation of default condition variable. It doesn't do a real
+// `wait`, instead it spins a short amount of time only.
+class ConditionVariableDummy
+    : public ConditionVariableBase<ConditionVariableDummy> {
+public:
+  void notifyAllImpl(UNUSED HybridMutex &M) REQUIRES(M) {}
+
+  void waitImpl(UNUSED HybridMutex &M) REQUIRES(M) {
+    M.unlock();
+
+    constexpr u32 SpinTimes = 64;
+    volatile u32 V = 0;
+    for (u32 I = 0; I < SpinTimes; ++I) {
+      u32 Tmp = V + 1;
+      V = Tmp;
+    }
+
+    M.lock();
+  }
+};
+
+template <typename Config, typename = const bool>
+struct ConditionVariableState {
+  static constexpr bool enabled() { return false; }
+  // This is only used for compilation purpose so that we won't end up having
+  // many conditional compilations. If you want to use `ConditionVariableDummy`,
+  // define `ConditionVariableT` in your allocator configuration. See
+  // allocator_config.h for more details.
+  using ConditionVariableT = ConditionVariableDummy;
+};
+
+template <typename Config>
+struct ConditionVariableState<Config, decltype(Config::UseConditionVariable)> {
+  static constexpr bool enabled() { return true; }
+  using ConditionVariableT = typename Config::ConditionVariableT;
+};
+
+} // namespace scudo
+
+#endif // SCUDO_CONDITION_VARIABLE_H_

compiler-rt/lib/scudo/standalone/condition_variable_base.h

@@ -0,0 +1,56 @@
+//===-- condition_variable_base.h -------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SCUDO_CONDITION_VARIABLE_BASE_H_
+#define SCUDO_CONDITION_VARIABLE_BASE_H_
+
+#include "mutex.h"
+#include "thread_annotations.h"
+
+namespace scudo {
+
+template <typename Derived> class ConditionVariableBase {
+public:
+  constexpr ConditionVariableBase() = default;
+
+  void bindTestOnly(HybridMutex &Mutex) {
+#if SCUDO_DEBUG
+    boundMutex = &Mutex;
+#else
+    (void)Mutex;
+#endif
+  }
+
+  void notifyAll(HybridMutex &M) REQUIRES(M) {
+#if SCUDO_DEBUG
+    CHECK_EQ(&M, boundMutex);
+#endif
+    getDerived()->notifyAllImpl(M);
+  }
+
+  void wait(HybridMutex &M) REQUIRES(M) {
+#if SCUDO_DEBUG
+    CHECK_EQ(&M, boundMutex);
+#endif
+    getDerived()->waitImpl(M);
+  }
+
+protected:
+  Derived *getDerived() { return static_cast<Derived *>(this); }
+
+#if SCUDO_DEBUG
+  // Because thread-safety analysis doesn't support pointer aliasing, we are not
+  // able to mark the proper annotations without false positive. Instead, we
+  // pass the lock and do the same-lock check separately.
+  HybridMutex *boundMutex = nullptr;
+#endif
+};
+
+} // namespace scudo
+
+#endif // SCUDO_CONDITION_VARIABLE_BASE_H_

compiler-rt/lib/scudo/standalone/condition_variable_linux.cpp

@@ -0,0 +1,52 @@
+//===-- condition_variable_linux.cpp ----------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "platform.h"
+
+#if SCUDO_LINUX
+
+#include "condition_variable_linux.h"
+
+#include "atomic_helpers.h"
+
+#include <limits.h>
+#include <linux/futex.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+namespace scudo {
+
+void ConditionVariableLinux::notifyAllImpl(UNUSED HybridMutex &M) {
+  const u32 V = atomic_load_relaxed(&Counter);
+  atomic_store_relaxed(&Counter, V + 1);
+
+  // TODO(chiahungduan): Move the waiters from the futex waiting queue
+  // `Counter` to futex waiting queue `M` so that the awoken threads won't be
+  // blocked again due to locked `M` by current thread.
+  if (LastNotifyAll != V) {
+    syscall(SYS_futex, reinterpret_cast<uptr>(&Counter), FUTEX_WAKE_PRIVATE,
+            INT_MAX, nullptr, nullptr, 0);
+  }
+
+  LastNotifyAll = V + 1;
+}
+
+void ConditionVariableLinux::waitImpl(HybridMutex &M) {
+  const u32 V = atomic_load_relaxed(&Counter) + 1;
+  atomic_store_relaxed(&Counter, V);
+
+  // TODO: Use ScopedUnlock when it's supported.
+  M.unlock();
+  syscall(SYS_futex, reinterpret_cast<uptr>(&Counter), FUTEX_WAIT_PRIVATE, V,
+          nullptr, nullptr, 0);
+  M.lock();
+}
+
+} // namespace scudo
+
+#endif // SCUDO_LINUX

compiler-rt/lib/scudo/standalone/condition_variable_linux.h

@@ -0,0 +1,38 @@
+//===-- condition_variable_linux.h ------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SCUDO_CONDITION_VARIABLE_LINUX_H_
+#define SCUDO_CONDITION_VARIABLE_LINUX_H_
+
+#include "platform.h"
+
+#if SCUDO_LINUX
+
+#include "atomic_helpers.h"
+#include "condition_variable_base.h"
+#include "thread_annotations.h"
+
+namespace scudo {
+
+class ConditionVariableLinux
+    : public ConditionVariableBase<ConditionVariableLinux> {
+public:
+  void notifyAllImpl(HybridMutex &M) REQUIRES(M);
+
+  void waitImpl(HybridMutex &M) REQUIRES(M);
+
+private:
+  u32 LastNotifyAll = 0;
+  atomic_u32 Counter = {};
+};
+
+} // namespace scudo
+
+#endif // SCUDO_LINUX
+
+#endif // SCUDO_CONDITION_VARIABLE_LINUX_H_