gio: gmemorymonitorpoll: Poll backend for the GMemoryMonitor

This backend periodically watch the memory free ratio through sysinfo().
It signals the applications when the memory free ratio drops to 40%, 30%,
and 20% for LOW, MEDIUM, CRITICAL status, respectively.

gio/giomodule.c

@@ -55,6 +55,9 @@
 #ifdef __linux__
 #include "gmemorymonitorpsi.h"
 #endif
+#ifdef HAVE_SYSINFO
+#include "gmemorymonitorpoll.h"
+#endif
 #include "gpowerprofilemonitor.h"
 #include "gpowerprofilemonitordbus.h"
 #include "gpowerprofilemonitorportal.h"
@@ -1087,6 +1090,9 @@ extern GType g_memory_monitor_dbus_get_type (void);
 #ifdef __linux__
 extern GType g_memory_monitor_psi_get_type (void);
 #endif
+#ifdef HAVE_SYSINFO
+extern GType g_memory_monitor_poll_get_type (void);
+#endif
 extern GType g_memory_monitor_portal_get_type (void);
 extern GType g_memory_monitor_win32_get_type (void);
 extern GType g_power_profile_monitor_dbus_get_type (void);
@@ -1369,6 +1375,9 @@ _g_io_modules_ensure_loaded (void)
       g_type_ensure (g_memory_monitor_dbus_get_type ());
 #ifdef __linux__
       g_type_ensure (g_memory_monitor_psi_get_type ());
+#endif
+#ifdef HAVE_SYSINFO
+      g_type_ensure (g_memory_monitor_poll_get_type ());
 #endif
       g_type_ensure (g_memory_monitor_portal_get_type ());
       g_type_ensure (g_network_monitor_portal_get_type ());

gio/gmemorymonitorpoll.c

@@ -0,0 +1,273 @@
+/* GIO - GLib Input, Output and Streaming Library
+ *
+ * Copyright 2025 Red Hat, Inc.
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+#include "config.h"
+
+#include "gcancellable.h"
+#include "gdbusnamewatching.h"
+#include "gdbusproxy.h"
+#include "ginitable.h"
+#include "gioerror.h"
+#include "giomodule-priv.h"
+#include "glib/gstdio.h"
+#include "glib/glib-private.h"
+#include "glibintl.h"
+#include "gmemorymonitor.h"
+#include "gmemorymonitorpoll.h"
+
+#include <fcntl.h>
+#include <unistd.h>
+
+/**
+ * GMemoryMonitorPoll:
+ *
+ * A [iface@Gio.MemoryMonitor] which polls the system free/used
+ * memory ratio on a fixed timer.
+ *
+ * It polls, for example, every 10 seconds, and emits different
+ * [signal@Gio.MemoryMonitor::low-memory-warning] signals if it falls below several
+ * ‘low’ thresholds.
+ *
+ * The system free/used memory ratio is queried using [`sysinfo()`](man:sysinfo(2)).
+ *
+ * This is intended as a fallback implementation of [iface@Gio.MemoryMonitor] in case
+ * other, more performant, implementations are not supported on the system.
+ *
+ * Since: 2.86
+ */
+
+typedef enum {
+  PROP_MEM_FREE_RATIO = 1,
+  PROP_POLL_INTERVAL_MS,
+} GMemoryMonitorPollProperty;
+
+#define G_MEMORY_MONITOR_POLL_GET_INITABLE_IFACE(o) (G_TYPE_INSTANCE_GET_INTERFACE ((o), G_TYPE_INITABLE, GInitable))
+
+static void g_memory_monitor_poll_iface_init (GMemoryMonitorInterface *iface);
+static void g_memory_monitor_poll_initable_iface_init (GInitableIface *iface);
+
+struct _GMemoryMonitorPoll
+{
+  GMemoryMonitorBase parent_instance;
+
+  GMainContext *worker;  /* (unowned) */
+  GSource *source_timeout;  /* (owned) */
+
+  /* it overrides the default timeout when running the test */
+  unsigned int poll_interval_ms;  /* zero to use the default */
+  gdouble mem_free_ratio;
+};
+
+/* the default monitor timeout */
+#define G_MEMORY_MONITOR_PSI_DEFAULT_SEC 10
+
+G_DEFINE_TYPE_WITH_CODE (GMemoryMonitorPoll, g_memory_monitor_poll, G_TYPE_MEMORY_MONITOR_BASE,
+                         G_IMPLEMENT_INTERFACE (G_TYPE_INITABLE,
+                                                g_memory_monitor_poll_initable_iface_init)
+                         G_IMPLEMENT_INTERFACE (G_TYPE_MEMORY_MONITOR,
+                                                g_memory_monitor_poll_iface_init)
+                         _g_io_modules_ensure_extension_points_registered ();
+                         g_io_extension_point_implement (G_MEMORY_MONITOR_EXTENSION_POINT_NAME,
+                                                         g_define_type_id,
+                                                         "poll",
+                                                         10))
+
+static void
+g_memory_monitor_poll_init (GMemoryMonitorPoll *mem_poll)
+{
+  mem_poll->mem_free_ratio = -1.0;
+}
+
+static void
+g_memory_monitor_poll_set_property (GObject      *object,
+                                    guint         prop_id,
+                                    const GValue *value,
+                                    GParamSpec   *pspec)
+{
+  GMemoryMonitorPoll *monitor = G_MEMORY_MONITOR_POLL (object);
+
+  switch ((GMemoryMonitorPollProperty) prop_id)
+    {
+    case PROP_MEM_FREE_RATIO:
+      monitor->mem_free_ratio = g_value_get_double (value);
+      break;
+    case PROP_POLL_INTERVAL_MS:
+      monitor->poll_interval_ms = g_value_get_uint (value);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+    }
+}
+
+static void
+g_memory_monitor_poll_get_property (GObject    *object,
+                                    guint       prop_id,
+                                    GValue     *value,
+                                    GParamSpec *pspec)
+{
+  GMemoryMonitorPoll *monitor = G_MEMORY_MONITOR_POLL (object);
+
+  switch ((GMemoryMonitorPollProperty) prop_id)
+    {
+    case PROP_MEM_FREE_RATIO:
+      g_value_set_double (value, monitor->mem_free_ratio);
+      break;
+    case PROP_POLL_INTERVAL_MS:
+      g_value_set_uint (value, monitor->poll_interval_ms);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+    }
+}
+
+static gboolean
+g_memory_monitor_mem_ratio_cb (gpointer data)
+{
+  GMemoryMonitorPoll *monitor = (GMemoryMonitorPoll *) data;
+  gdouble mem_ratio;
+  GMemoryMonitorLowMemoryLevel warning_level = G_MEMORY_MONITOR_LOW_MEMORY_LEVEL_INVALID;
+
+  /* Should be executed in the worker context */
+  g_assert (g_main_context_is_owner (monitor->worker));
+
+  mem_ratio = g_memory_monitor_base_query_mem_ratio ();
+
+  if (mem_ratio < 0.0)
+    return G_SOURCE_REMOVE;
+
+  if (mem_ratio > 0.5)
+    return G_SOURCE_CONTINUE;
+
+  /* free ratio override */
+  if (monitor->mem_free_ratio >= 0.0)
+    mem_ratio = monitor->mem_free_ratio;
+
+  g_debug ("memory free ratio %f", mem_ratio);
+
+  if (mem_ratio < 0.2)
+    warning_level = G_MEMORY_MONITOR_LOW_MEMORY_LEVEL_CRITICAL;
+  else if (mem_ratio < 0.3)
+    warning_level = G_MEMORY_MONITOR_LOW_MEMORY_LEVEL_MEDIUM;
+  else if (mem_ratio < 0.4)
+    warning_level = G_MEMORY_MONITOR_LOW_MEMORY_LEVEL_LOW;
+
+  if (warning_level != G_MEMORY_MONITOR_LOW_MEMORY_LEVEL_INVALID)
+    g_memory_monitor_base_send_event_to_user (G_MEMORY_MONITOR_BASE (monitor), warning_level);
+
+  return G_SOURCE_CONTINUE;
+}
+
+static gboolean
+g_memory_monitor_poll_initable_init (GInitable     *initable,
+                                     GCancellable  *cancellable,
+                                     GError       **error)
+{
+  GMemoryMonitorPoll *monitor = G_MEMORY_MONITOR_POLL (initable);
+  GSource *source;
+
+  if (monitor->poll_interval_ms > 0)
+    {
+      if (monitor->poll_interval_ms < G_TIME_SPAN_MILLISECOND)
+        source = g_timeout_source_new (monitor->poll_interval_ms);
+      else
+        source = g_timeout_source_new_seconds (monitor->poll_interval_ms / G_TIME_SPAN_MILLISECOND);
+    }
+  else
+    {
+      /* default 10 second */
+      source = g_timeout_source_new_seconds (G_MEMORY_MONITOR_PSI_DEFAULT_SEC);
+    }
+
+  g_source_set_callback (source, g_memory_monitor_mem_ratio_cb, monitor, NULL);
+  monitor->worker = GLIB_PRIVATE_CALL (g_get_worker_context) ();
+  g_source_attach (source, monitor->worker);
+  monitor->source_timeout = g_steal_pointer (&source);
+
+  return TRUE;
+}
+
+static void
+g_memory_monitor_poll_finalize (GObject *object)
+{
+  GMemoryMonitorPoll *monitor = G_MEMORY_MONITOR_POLL (object);
+
+  g_source_destroy (monitor->source_timeout);
+  g_source_unref (monitor->source_timeout);
+
+  G_OBJECT_CLASS (g_memory_monitor_poll_parent_class)->finalize (object);
+}
+
+static void
+g_memory_monitor_poll_class_init (GMemoryMonitorPollClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+
+  object_class->set_property = g_memory_monitor_poll_set_property;
+  object_class->get_property = g_memory_monitor_poll_get_property;
+  object_class->finalize = g_memory_monitor_poll_finalize;
+
+  /**
+   * GMemoryMonitorPoll:mem-free-ratio:
+   *
+   * Override the memory free ratio
+   *
+   * Since: 2.86
+   */
+  g_object_class_install_property (object_class,
+                                   PROP_MEM_FREE_RATIO,
+                                   g_param_spec_double ("mem-free-ratio", NULL, NULL,
+                                                        -1.0, 1.0,
+                                                        -1.0,
+                                                        G_PARAM_READWRITE |
+                                                        G_PARAM_CONSTRUCT_ONLY |
+                                                        G_PARAM_STATIC_STRINGS));
+
+  /**
+   * GMemoryMonitorPoll:poll-interval-ms:
+   *
+   * Override the poll interval for monitoring the memory usage.
+   *
+   * The interval is in milliseconds. Zero means to use the default interval.
+   *
+   * Since: 2.86
+   */
+  g_object_class_install_property (object_class,
+                                   PROP_POLL_INTERVAL_MS,
+                                   g_param_spec_uint ("poll-interval-ms", NULL, NULL,
+                                                      0, G_MAXUINT,
+                                                      0,
+                                                      G_PARAM_READWRITE |
+                                                      G_PARAM_CONSTRUCT_ONLY |
+                                                      G_PARAM_STATIC_STRINGS));
+
+}
+
+static void
+g_memory_monitor_poll_iface_init (GMemoryMonitorInterface *monitor_iface)
+{
+}
+
+static void
+g_memory_monitor_poll_initable_iface_init (GInitableIface *iface)
+{
+  iface->init = g_memory_monitor_poll_initable_init;
+}
+

gio/gmemorymonitorpoll.h

@@ -0,0 +1,38 @@
+/* GIO - GLib Input, Output and Streaming Library
+ *
+ * Copyright 2025 Red Hat, Inc.
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __G_MEMORY_MONITOR_POLL_H__
+#define __G_MEMORY_MONITOR_POLL_H__
+
+#include "gmemorymonitorbase.h"
+
+#include <glib-object.h>
+
+G_BEGIN_DECLS
+
+#define G_TYPE_MEMORY_MONITOR_POLL         (g_memory_monitor_poll_get_type ())
+G_DECLARE_FINAL_TYPE (GMemoryMonitorPoll, g_memory_monitor_poll, G, MEMORY_MONITOR_POLL, GMemoryMonitorBase)
+
+GIO_AVAILABLE_IN_2_86
+GType g_memory_monitor_poll_get_type (void);
+
+G_END_DECLS
+
+#endif /* __G_MEMORY_MONITOR_PSI_H__ */

gio/meson.build

@@ -391,6 +391,12 @@ if host_system != 'windows'
     'gunixoutputstream.h',
   )
 
+  if glib_conf.has('HAVE_SYSINFO')
+    unix_sources += files(
+      'gmemorymonitorpoll.c',
+    )
+  endif
+
   if glib_have_cocoa
     settings_sources += files('gnextstepsettingsbackend.m')
     contenttype_sources += files('gcontenttype-osx.m')