forked from OSchip/llvm-project
103 lines
3.2 KiB
C++
103 lines
3.2 KiB
C++
//===-- xray_buffer_queue.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 interface for a buffer queue implementation.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
#ifndef XRAY_BUFFER_QUEUE_H
|
|
#define XRAY_BUFFER_QUEUE_H
|
|
|
|
#include <atomic>
|
|
#include <cstdint>
|
|
#include <deque>
|
|
#include <mutex>
|
|
#include <system_error>
|
|
#include <unordered_set>
|
|
#include <utility>
|
|
|
|
namespace __xray {
|
|
|
|
/// BufferQueue implements a circular queue of fixed sized buffers (much like a
|
|
/// freelist) but is concerned mostly with making it really quick to initialise,
|
|
/// finalise, and get/return buffers to the queue. This is one key component of
|
|
/// the "flight data recorder" (FDR) mode to support ongoing XRay function call
|
|
/// trace collection.
|
|
class BufferQueue {
|
|
public:
|
|
struct Buffer {
|
|
void *Buffer = nullptr;
|
|
std::size_t Size = 0;
|
|
};
|
|
|
|
private:
|
|
std::size_t BufferSize;
|
|
|
|
// We use a bool to indicate whether the Buffer has been used in this
|
|
// freelist implementation.
|
|
std::deque<std::tuple<Buffer, bool>> Buffers;
|
|
std::mutex Mutex;
|
|
std::unordered_set<void *> OwnedBuffers;
|
|
std::atomic<bool> Finalizing;
|
|
|
|
public:
|
|
/// Initialise a queue of size |N| with buffers of size |B|. We report success
|
|
/// through |Success|.
|
|
BufferQueue(std::size_t B, std::size_t N, bool &Success);
|
|
|
|
/// Updates |Buf| to contain the pointer to an appropriate buffer. Returns an
|
|
/// error in case there are no available buffers to return when we will run
|
|
/// over the upper bound for the total buffers.
|
|
///
|
|
/// Requirements:
|
|
/// - BufferQueue is not finalising.
|
|
///
|
|
/// Returns:
|
|
/// - std::errc::not_enough_memory on exceeding MaxSize.
|
|
/// - no error when we find a Buffer.
|
|
/// - std::errc::state_not_recoverable on finalising BufferQueue.
|
|
std::error_code getBuffer(Buffer &Buf);
|
|
|
|
/// Updates |Buf| to point to nullptr, with size 0.
|
|
///
|
|
/// Returns:
|
|
/// - ...
|
|
std::error_code releaseBuffer(Buffer &Buf);
|
|
|
|
bool finalizing() const { return Finalizing.load(std::memory_order_acquire); }
|
|
|
|
/// Sets the state of the BufferQueue to finalizing, which ensures that:
|
|
///
|
|
/// - All subsequent attempts to retrieve a Buffer will fail.
|
|
/// - All releaseBuffer operations will not fail.
|
|
///
|
|
/// After a call to finalize succeeds, all subsequent calls to finalize will
|
|
/// fail with std::errc::state_not_recoverable.
|
|
std::error_code finalize();
|
|
|
|
/// Applies the provided function F to each Buffer in the queue, only if the
|
|
/// Buffer is marked 'used' (i.e. has been the result of getBuffer(...) and a
|
|
/// releaseBuffer(...) operation.
|
|
template <class F> void apply(F Fn) {
|
|
std::lock_guard<std::mutex> G(Mutex);
|
|
for (const auto &T : Buffers) {
|
|
if (std::get<1>(T))
|
|
Fn(std::get<0>(T));
|
|
}
|
|
}
|
|
|
|
// Cleans up allocated buffers.
|
|
~BufferQueue();
|
|
};
|
|
|
|
} // namespace __xray
|
|
|
|
#endif // XRAY_BUFFER_QUEUE_H
|