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