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//===-- xray_allocator.h ---------------------------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file is a part of XRay, a dynamic runtime instrumentation system.
//
// Defines the allocator interface for an arena allocator, used primarily for
// the profiling runtime.
//
//===----------------------------------------------------------------------===//
#ifndef XRAY_ALLOCATOR_H
#define XRAY_ALLOCATOR_H
#include "sanitizer_common/sanitizer_common.h"
#include "sanitizer_common/sanitizer_internal_defs.h"
#include "sanitizer_common/sanitizer_mutex.h"
#include "sanitizer_common/sanitizer_posix.h"
#include "xray_defs.h"
#include "xray_utils.h"
#include <cstddef>
#include <cstdint>
#include <sys/mman.h>
namespace __xray {
// We implement our own memory allocation routine which will bypass the
// internal allocator. This allows us to manage the memory directly, using
// mmap'ed memory to back the allocators.
template <class T> T *allocate() XRAY_NEVER_INSTRUMENT {
uptr RoundedSize = RoundUpTo(sizeof(T), GetPageSizeCached());
uptr B = internal_mmap(NULL, RoundedSize, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
int ErrNo;
if (UNLIKELY(internal_iserror(B, &ErrNo))) {
if (Verbosity())
Report(
"XRay Profiling: Failed to allocate memory of size %d; Error = %d.\n",
RoundedSize, B);
return nullptr;
}
return reinterpret_cast<T *>(B);
}
template <class T> void deallocate(T *B) XRAY_NEVER_INSTRUMENT {
if (B == nullptr)
return;
uptr RoundedSize = RoundUpTo(sizeof(T), GetPageSizeCached());
internal_munmap(B, RoundedSize);
}
template <class T = uint8_t> T *allocateBuffer(size_t S) XRAY_NEVER_INSTRUMENT {
uptr RoundedSize = RoundUpTo(S * sizeof(T), GetPageSizeCached());
uptr B = internal_mmap(NULL, RoundedSize, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
int ErrNo;
if (UNLIKELY(internal_iserror(B, &ErrNo))) {
if (Verbosity())
Report(
"XRay Profiling: Failed to allocate memory of size %d; Error = %d.\n",
RoundedSize, B);
return nullptr;
}
return reinterpret_cast<T *>(B);
}
template <class T> void deallocateBuffer(T *B, size_t S) XRAY_NEVER_INSTRUMENT {
if (B == nullptr)
return;
uptr RoundedSize = RoundUpTo(S * sizeof(T), GetPageSizeCached());
internal_munmap(B, RoundedSize);
}
template <class T, class... U>
T *initArray(size_t N, U &&... Us) XRAY_NEVER_INSTRUMENT {
auto A = allocateBuffer<T>(N);
if (A != nullptr)
while (N > 0)
new (A + (--N)) T(std::forward<U>(Us)...);
return A;
}
/// The Allocator type hands out fixed-sized chunks of memory that are
/// cache-line aligned and sized. This is useful for placement of
/// performance-sensitive data in memory that's frequently accessed. The
/// allocator also self-limits the peak memory usage to a dynamically defined
/// maximum.
///
/// N is the lower-bound size of the block of memory to return from the
/// allocation function. N is used to compute the size of a block, which is
/// cache-line-size multiples worth of memory. We compute the size of a block by
/// determining how many cache lines worth of memory is required to subsume N.
///
/// The Allocator instance will manage its own memory acquired through mmap.
/// This severely constrains the platforms on which this can be used to POSIX
/// systems where mmap semantics are well-defined.
///
/// FIXME: Isolate the lower-level memory management to a different abstraction
/// that can be platform-specific.
template <size_t N> struct Allocator {
// The Allocator returns memory as Block instances.
struct Block {
/// Compute the minimum cache-line size multiple that is >= N.
static constexpr auto Size = nearest_boundary(N, kCacheLineSize);
void *Data;
};
private:
const size_t MaxMemory{0};
uint8_t *BackingStore = nullptr;
uint8_t *AlignedNextBlock = nullptr;
size_t AllocatedBlocks = 0;
SpinMutex Mutex{};
void *Alloc() XRAY_NEVER_INSTRUMENT {
SpinMutexLock Lock(&Mutex);
if (UNLIKELY(BackingStore == nullptr)) {
BackingStore = allocateBuffer(MaxMemory);
if (BackingStore == nullptr) {
if (Verbosity())
Report("XRay Profiling: Failed to allocate memory for allocator.\n");
return nullptr;
}
AlignedNextBlock = BackingStore;
// Ensure that NextBlock is aligned appropriately.
auto BackingStoreNum = reinterpret_cast<uintptr_t>(BackingStore);
auto AlignedNextBlockNum = nearest_boundary(
reinterpret_cast<uintptr_t>(AlignedNextBlock), kCacheLineSize);
if (diff(AlignedNextBlockNum, BackingStoreNum) > ptrdiff_t(MaxMemory)) {
deallocateBuffer(BackingStore, MaxMemory);
AlignedNextBlock = BackingStore = nullptr;
if (Verbosity())
Report("XRay Profiling: Cannot obtain enough memory from "
"preallocated region.\n");
return nullptr;
}
AlignedNextBlock = reinterpret_cast<uint8_t *>(AlignedNextBlockNum);
// Assert that AlignedNextBlock is cache-line aligned.
DCHECK_EQ(reinterpret_cast<uintptr_t>(AlignedNextBlock) % kCacheLineSize,
0);
}
if ((AllocatedBlocks * Block::Size) >= MaxMemory)
return nullptr;
// Align the pointer we'd like to return to an appropriate alignment, then
// advance the pointer from where to start allocations.
void *Result = AlignedNextBlock;
AlignedNextBlock = reinterpret_cast<uint8_t *>(
reinterpret_cast<uint8_t *>(AlignedNextBlock) + N);
++AllocatedBlocks;
return Result;
}
public:
explicit Allocator(size_t M) XRAY_NEVER_INSTRUMENT
: MaxMemory(nearest_boundary(M, kCacheLineSize)) {}
Block Allocate() XRAY_NEVER_INSTRUMENT { return {Alloc()}; }
~Allocator() NOEXCEPT XRAY_NEVER_INSTRUMENT {
if (BackingStore != nullptr) {
deallocateBuffer(BackingStore, MaxMemory);
}
}
};
} // namespace __xray
#endif // XRAY_ALLOCATOR_H
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