1 /* GIO - GLib Input, Output and Streaming Library
2 *
3 * Copyright 2019 Red Hat, Inc
4 *
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2.1 of the License, or (at your option) any later version.
9 *
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
14 *
15 * You should have received a copy of the GNU Lesser General
16 * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
17 */
18
19 #include "config.h"
20 #include "glib.h"
21 #include "glibintl.h"
22
23 #include "gmemorymonitor.h"
24 #include "ginetaddress.h"
25 #include "ginetsocketaddress.h"
26 #include "ginitable.h"
27 #include "gioenumtypes.h"
28 #include "giomodule-priv.h"
29 #include "gtask.h"
30
31 /**
32 * SECTION:gmemorymonitor
33 * @title: GMemoryMonitor
34 * @short_description: Memory usage monitor
35 * @include: gio/gio.h
36 *
37 * #GMemoryMonitor will monitor system memory and suggest to the application
38 * when to free memory so as to leave more room for other applications.
39 * It is implemented on Linux using the [Low Memory Monitor](https://gitlab.freedesktop.org/hadess/low-memory-monitor/)
40 * ([API documentation](https://hadess.pages.freedesktop.org/low-memory-monitor/)).
41 *
42 * There is also an implementation for use inside Flatpak sandboxes.
43 *
44 * Possible actions to take when the signal is received are:
45 * - Free caches
46 * - Save files that haven't been looked at in a while to disk, ready to be reopened when needed
47 * - Run a garbage collection cycle
48 * - Try and compress fragmented allocations
49 * - Exit on idle if the process has no reason to stay around
50 * - Call [`malloc_trim(3)`](man:malloc_trim) to return cached heap pages to
51 * the kernel (if supported by your libc)
52 *
53 * Note that some actions may not always improve system performance, and so
54 * should be profiled for your application. `malloc_trim()`, for example, may
55 * make future heap allocations slower (due to releasing cached heap pages back
56 * to the kernel).
57 *
58 * See #GMemoryMonitorWarningLevel for details on the various warning levels.
59 *
60 * |[<!-- language="C" -->
61 * static void
62 * warning_cb (GMemoryMonitor *m, GMemoryMonitorWarningLevel level)
63 * {
64 * g_debug ("Warning level: %d", level);
65 * if (warning_level > G_MEMORY_MONITOR_WARNING_LEVEL_LOW)
66 * drop_caches ();
67 * }
68 *
69 * static GMemoryMonitor *
70 * monitor_low_memory (void)
71 * {
72 * GMemoryMonitor *m;
73 * m = g_memory_monitor_dup_default ();
74 * g_signal_connect (G_OBJECT (m), "low-memory-warning",
75 * G_CALLBACK (warning_cb), NULL);
76 * return m;
77 * }
78 * ]|
79 *
80 * Don't forget to disconnect the #GMemoryMonitor::low-memory-warning
81 * signal, and unref the #GMemoryMonitor itself when exiting.
82 *
83 * Since: 2.64
84 */
85
86 /**
87 * GMemoryMonitor:
88 *
89 * #GMemoryMonitor monitors system memory and indicates when
90 * the system is low on memory.
91 *
92 * Since: 2.64
93 */
94
95 /**
96 * GMemoryMonitorInterface:
97 * @g_iface: The parent interface.
98 * @low_memory_warning: the virtual function pointer for the
99 * #GMemoryMonitor::low-memory-warning signal.
100 *
101 * The virtual function table for #GMemoryMonitor.
102 *
103 * Since: 2.64
104 */
105
106 G_DEFINE_INTERFACE_WITH_CODE (GMemoryMonitor, g_memory_monitor, G_TYPE_OBJECT,
107 g_type_interface_add_prerequisite (g_define_type_id, G_TYPE_INITABLE))
108
109 enum {
110 LOW_MEMORY_WARNING,
111 LAST_SIGNAL
112 };
113
114 static guint signals[LAST_SIGNAL] = { 0 };
115
116 /**
117 * g_memory_monitor_dup_default:
118 *
119 * Gets a reference to the default #GMemoryMonitor for the system.
120 *
121 * Returns: (not nullable) (transfer full): a new reference to the default #GMemoryMonitor
122 *
123 * Since: 2.64
124 */
125 GMemoryMonitor *
g_memory_monitor_dup_default(void)126 g_memory_monitor_dup_default (void)
127 {
128 return g_object_ref (_g_io_module_get_default (G_MEMORY_MONITOR_EXTENSION_POINT_NAME,
129 "GIO_USE_MEMORY_MONITOR",
130 NULL));
131 }
132
133 static void
g_memory_monitor_default_init(GMemoryMonitorInterface * iface)134 g_memory_monitor_default_init (GMemoryMonitorInterface *iface)
135 {
136 /**
137 * GMemoryMonitor::low-memory-warning:
138 * @monitor: a #GMemoryMonitor
139 * @level: the #GMemoryMonitorWarningLevel warning level
140 *
141 * Emitted when the system is running low on free memory. The signal
142 * handler should then take the appropriate action depending on the
143 * warning level. See the #GMemoryMonitorWarningLevel documentation for
144 * details.
145 *
146 * Since: 2.64
147 */
148 signals[LOW_MEMORY_WARNING] =
149 g_signal_new (I_("low-memory-warning"),
150 G_TYPE_MEMORY_MONITOR,
151 G_SIGNAL_RUN_LAST,
152 G_STRUCT_OFFSET (GMemoryMonitorInterface, low_memory_warning),
153 NULL, NULL,
154 NULL,
155 G_TYPE_NONE, 1,
156 G_TYPE_MEMORY_MONITOR_WARNING_LEVEL);
157 }
158