[Lldb-commits] [lldb] [lldb-dap] Implement a MemoryMonitor for macOS & Linux (PR #129332)
Jonas Devlieghere via lldb-commits
lldb-commits at lists.llvm.org
Fri Feb 28 15:08:30 PST 2025
https://github.com/JDevlieghere updated https://github.com/llvm/llvm-project/pull/129332
>From c63350db79ac6bcc6f180cc84a37e829d1c8b2a8 Mon Sep 17 00:00:00 2001
From: Jonas Devlieghere <jonas at devlieghere.com>
Date: Fri, 28 Feb 2025 14:54:42 -0600
Subject: [PATCH 1/2] [lldb-dap] Implement a MemoryMonitor for macOS & Linux
This implements a memory monitor for macOS & Linux, and registers a
callback that invokes SBDebugger::MemoryPressureDetected() when a low
memory event is detected.
---
lldb/tools/lldb-dap/CMakeLists.txt | 1 +
lldb/tools/lldb-dap/MemoryMonitor.cpp | 114 ++++++++++++++++++++++++++
lldb/tools/lldb-dap/MemoryMonitor.h | 41 +++++++++
lldb/tools/lldb-dap/lldb-dap.cpp | 17 +++-
4 files changed, 171 insertions(+), 2 deletions(-)
create mode 100644 lldb/tools/lldb-dap/MemoryMonitor.cpp
create mode 100644 lldb/tools/lldb-dap/MemoryMonitor.h
diff --git a/lldb/tools/lldb-dap/CMakeLists.txt b/lldb/tools/lldb-dap/CMakeLists.txt
index 8b3c520ec4360..8db377e31c3c6 100644
--- a/lldb/tools/lldb-dap/CMakeLists.txt
+++ b/lldb/tools/lldb-dap/CMakeLists.txt
@@ -36,6 +36,7 @@ add_lldb_tool(lldb-dap
RunInTerminal.cpp
SourceBreakpoint.cpp
Watchpoint.cpp
+ MemoryMonitor.cpp
Handler/ResponseHandler.cpp
Handler/AttachRequestHandler.cpp
diff --git a/lldb/tools/lldb-dap/MemoryMonitor.cpp b/lldb/tools/lldb-dap/MemoryMonitor.cpp
new file mode 100644
index 0000000000000..da3da42fe9b0f
--- /dev/null
+++ b/lldb/tools/lldb-dap/MemoryMonitor.cpp
@@ -0,0 +1,114 @@
+//===-- 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 "MemoryMonitor.h"
+#include "llvm/ADT/ScopeExit.h"
+#include <atomic>
+#include <cstdio>
+#include <cstring>
+#include <thread>
+
+#if defined(__APPLE__)
+#include <dispatch/dispatch.h>
+#endif
+
+#if defined(__linux__)
+#include <fcntl.h>
+#include <poll.h>
+#include <unistd.h>
+#endif
+
+using namespace lldb_dap;
+
+#if defined(__APPLE__)
+class MemoryMonitorDarwin : public MemoryMonitor {
+ using MemoryMonitor::MemoryMonitor;
+ void Start() override {
+ m_memory_pressure_source = dispatch_source_create(
+ DISPATCH_SOURCE_TYPE_MEMORYPRESSURE,
+ 0, // system-wide monitoring
+ DISPATCH_MEMORYPRESSURE_WARN | DISPATCH_MEMORYPRESSURE_CRITICAL,
+ dispatch_get_main_queue());
+
+ dispatch_source_set_event_handler(m_memory_pressure_source, ^{
+ dispatch_source_memorypressure_flags_t pressureLevel =
+ dispatch_source_get_data(m_memory_pressure_source);
+ if (pressureLevel &
+ (DISPATCH_MEMORYPRESSURE_WARN | DISPATCH_MEMORYPRESSURE_CRITICAL)) {
+ m_callback();
+ }
+ });
+ }
+
+ void Stop() override { dispatch_source_cancel(m_memory_pressure_source); }
+
+private:
+ dispatch_source_t m_memory_pressure_source;
+};
+#endif
+
+#if defined(__linux__)
+static void MonitorThread(std::atomic<bool> &done,
+ MemoryMonitor::Callback callback) {
+ 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 (!done) {
+ int n = poll(&fds, 1, 1000);
+ if (n > 0) {
+ if (fds.revents & POLLERR)
+ return;
+ if (fds.revents & POLLPRI)
+ callback();
+ }
+ }
+}
+
+class MemoryMonitorLinux : public MemoryMonitor {
+public:
+ using MemoryMonitor::MemoryMonitor;
+
+ void Start() override {
+ m_memory_pressure_thread =
+ std::thread(MonitorThread, std::ref(m_done), m_callback);
+ }
+
+ void Stop() override {
+ if (m_memory_pressure_thread.joinable()) {
+ m_done = true;
+ m_memory_pressure_thread.join();
+ }
+ }
+
+private:
+ std::atomic<bool> m_done = false;
+ std::thread m_memory_pressure_thread;
+};
+#endif
+
+std::unique_ptr<MemoryMonitor> MemoryMonitor::Create(Callback callback) {
+#if defined(__APPLE__)
+ return std::make_unique<MemoryMonitorDarwin>(callback);
+#endif
+
+#if defined(__linux__)
+ return std::make_unique<MemoryMonitorLinux>(callback);
+#endif
+
+ return nullptr;
+}
diff --git a/lldb/tools/lldb-dap/MemoryMonitor.h b/lldb/tools/lldb-dap/MemoryMonitor.h
new file mode 100644
index 0000000000000..e07c3bde9e85c
--- /dev/null
+++ b/lldb/tools/lldb-dap/MemoryMonitor.h
@@ -0,0 +1,41 @@
+//===-- MemoryMonitor.h ---------------------------------------------------===//
+//
+// 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 LLDB_TOOLS_LLDB_DAP_WATCHPOINT_H
+#define LLDB_TOOLS_LLDB_DAP_WATCHPOINT_H
+
+#include <functional>
+#include <memory>
+
+namespace lldb_dap {
+
+class MemoryMonitor {
+public:
+ using Callback = std::function<void()>;
+
+ MemoryMonitor(Callback callback) : m_callback(callback) {}
+ virtual ~MemoryMonitor() = default;
+
+ /// MemoryMonitor is not copyable.
+ /// @{
+ MemoryMonitor(const MemoryMonitor &) = delete;
+ MemoryMonitor &operator=(const MemoryMonitor &) = delete;
+ /// @}
+
+ static std::unique_ptr<MemoryMonitor> Create(Callback callback);
+
+ virtual void Start() = 0;
+ virtual void Stop() = 0;
+
+protected:
+ Callback m_callback;
+};
+
+} // namespace lldb_dap
+
+#endif
diff --git a/lldb/tools/lldb-dap/lldb-dap.cpp b/lldb/tools/lldb-dap/lldb-dap.cpp
index d005eccfae903..41405df548da2 100644
--- a/lldb/tools/lldb-dap/lldb-dap.cpp
+++ b/lldb/tools/lldb-dap/lldb-dap.cpp
@@ -9,7 +9,9 @@
#include "DAP.h"
#include "EventHelper.h"
#include "Handler/RequestHandler.h"
+#include "MemoryMonitor.h"
#include "RunInTerminal.h"
+#include "lldb/API/SBDebugger.h"
#include "lldb/API/SBStream.h"
#include "lldb/Host/Config.h"
#include "lldb/Host/File.h"
@@ -504,9 +506,20 @@ int main(int argc, char *argv[]) {
return EXIT_FAILURE;
}
+ // Create a memory monitor. This can return nullptr if the host platform is
+ // not supported.
+ std::unique_ptr<MemoryMonitor> memory_monitor = MemoryMonitor::Create(
+ []() { lldb::SBDebugger::MemoryPressureDetected(); });
+
+ if (memory_monitor)
+ memory_monitor->Start();
+
// Terminate the debugger before the C++ destructor chain kicks in.
- auto terminate_debugger =
- llvm::make_scope_exit([] { lldb::SBDebugger::Terminate(); });
+ auto terminate_debugger = llvm::make_scope_exit([&] {
+ if (memory_monitor)
+ memory_monitor->Stop();
+ lldb::SBDebugger::Terminate();
+ });
std::vector<std::string> pre_init_commands;
for (const std::string &arg :
>From 59594877e40c60c29832f37a8ff5f1eb495f69f9 Mon Sep 17 00:00:00 2001
From: Jonas Devlieghere <jonas at devlieghere.com>
Date: Fri, 28 Feb 2025 17:07:55 -0600
Subject: [PATCH 2/2] Use the dispatch_get_global_queue and call
dispatch_release
---
lldb/tools/lldb-dap/MemoryMonitor.cpp | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/lldb/tools/lldb-dap/MemoryMonitor.cpp b/lldb/tools/lldb-dap/MemoryMonitor.cpp
index da3da42fe9b0f..a9118a89a82ac 100644
--- a/lldb/tools/lldb-dap/MemoryMonitor.cpp
+++ b/lldb/tools/lldb-dap/MemoryMonitor.cpp
@@ -33,7 +33,10 @@ class MemoryMonitorDarwin : public MemoryMonitor {
DISPATCH_SOURCE_TYPE_MEMORYPRESSURE,
0, // system-wide monitoring
DISPATCH_MEMORYPRESSURE_WARN | DISPATCH_MEMORYPRESSURE_CRITICAL,
- dispatch_get_main_queue());
+ dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0));
+
+ if (!m_memory_pressure_source)
+ return;
dispatch_source_set_event_handler(m_memory_pressure_source, ^{
dispatch_source_memorypressure_flags_t pressureLevel =
@@ -45,7 +48,12 @@ class MemoryMonitorDarwin : public MemoryMonitor {
});
}
- void Stop() override { dispatch_source_cancel(m_memory_pressure_source); }
+ void Stop() override {
+ if (m_memory_pressure_source) {
+ dispatch_source_cancel(m_memory_pressure_source);
+ dispatch_release(m_memory_pressure_source);
+ }
+ }
private:
dispatch_source_t m_memory_pressure_source;
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