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//===-- MemoryMonitor.cpp -------------------------------------------------===//
//
// 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 "lldb/Host/MemoryMonitor.h"
#include "lldb/Host/HostThread.h"
#include "lldb/Host/ThreadLauncher.h"
#include "lldb/Utility/LLDBLog.h"
#include "lldb/Utility/Log.h"
#include "llvm/ADT/ScopeExit.h"
#include "llvm/Support/Error.h"
#include <atomic>
#include <cstddef>
#include <cstdio>
#include <cstring>
#if defined(__linux__)
#include <fcntl.h>
#include <poll.h>
#include <unistd.h>
#endif
#if defined(_WIN32)
#include <windows.h>
#endif
using namespace lldb_private;
class MemoryMonitorPoll : public MemoryMonitor {
public:
using MemoryMonitor::MemoryMonitor;
lldb::thread_result_t MonitorThread() {
#if defined(__linux__)
struct pollfd fds;
fds.fd = open("/proc/pressure/memory", O_RDWR | O_NONBLOCK);
if (fds.fd < 0)
return {};
fds.events = POLLPRI;
auto cleanup = llvm::make_scope_exit([&]() { close(fds.fd); });
// Detect a 50ms stall in a 2 second time window.
const char trig[] = "some 50000 2000000";
if (write(fds.fd, trig, strlen(trig) + 1) < 0)
return {};
while (!m_done) {
int n = poll(&fds, 1, g_timeout);
if (n > 0) {
if (fds.revents & POLLERR)
return {};
if (fds.revents & POLLPRI)
m_callback();
}
}
#endif
#if defined(_WIN32)
HANDLE low_memory_notification =
CreateMemoryResourceNotification(LowMemoryResourceNotification);
if (!low_memory_notification)
return {};
while (!m_done) {
if (WaitForSingleObject(low_memory_notification, g_timeout) ==
WAIT_OBJECT_0) {
m_callback();
}
}
#endif
return {};
}
void Start() override {
llvm::Expected<HostThread> memory_monitor_thread =
ThreadLauncher::LaunchThread("lldb.debugger.memory-monitor",
[this] { return MonitorThread(); });
if (memory_monitor_thread) {
m_memory_monitor_thread = *memory_monitor_thread;
} else {
LLDB_LOG_ERROR(GetLog(LLDBLog::Host), memory_monitor_thread.takeError(),
"failed to launch host thread: {0}");
}
}
void Stop() override {
if (m_memory_monitor_thread.IsJoinable()) {
m_done = true;
m_memory_monitor_thread.Join(nullptr);
}
}
private:
static constexpr uint32_t g_timeout = 1000;
std::atomic<bool> m_done = false;
HostThread m_memory_monitor_thread;
};
#if !defined(__APPLE__)
std::unique_ptr<MemoryMonitor> MemoryMonitor::Create(Callback callback) {
return std::make_unique<MemoryMonitorPoll>(callback);
}
#endif
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