/* 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 "glibintl.h"

#include "glib/glib-private.h"

#include "glib/gstdio.h"

#include "gmemorymonitor.h"

#include "gmemorymonitorbase.h"

#include "gmemorymonitorpsi.h"

#include <errno.h>

#include <fcntl.h>

#include <unistd.h>

/**

 * GMemoryMonitorPsi:

 *

 * A Linux [iface@Gio.MemoryMonitor] which uses the kernel

 * [pressure stall information](https://www.kernel.org/doc/html/latest/accounting/psi.html) (PSI).

 *

 * When it receives a PSI event, it emits

 * [signal@Gio.MemoryMonitor::low-memory-warning] with an appropriate warning

 * level.

 *

 * Since: 2.86

 */

/* Unprivileged users can also create monitors, with

 * the only limitation that the window size must be a

 * `multiple of 2s`, in order to prevent excessive resource usage.

 * see: https://www.kernel.org/doc/html/latest/accounting/psi.html*/

#define PSI_WINDOW_SEC 2

typedef enum {

  PROP_PROC_PATH = 1,

} GMemoryMonitorPsiProperty;

typedef enum

{

  MEMORY_PRESSURE_MONITOR_TRIGGER_SOME,

  MEMORY_PRESSURE_MONITOR_TRIGGER_FULL,

  MEMORY_PRESSURE_MONITOR_TRIGGER_MFD

} MemoryPressureMonitorTriggerType;

/* Each trigger here results in an open fd for the lifetime

 * of the `GMemoryMonitor`, so don’t add too many */

static const struct

{

  MemoryPressureMonitorTriggerType trigger_type;

  int threshold_ms;

} triggers[G_MEMORY_MONITOR_LOW_MEMORY_LEVEL_COUNT] = {

  { MEMORY_PRESSURE_MONITOR_TRIGGER_SOME, 70 },  /* 70ms out of 2sec for partial stall */

  { MEMORY_PRESSURE_MONITOR_TRIGGER_SOME, 100 }, /* 100ms out of 2sec for partial stall */

  { MEMORY_PRESSURE_MONITOR_TRIGGER_FULL, 100 }, /* 100ms out of 2sec for complete stall */

};

typedef struct

{

  GSource source;

  GPollFD *pollfd;

  GMemoryMonitorLowMemoryLevel level_type;

  GWeakRef monitor_weak;

} MemoryMonitorSource;

typedef gboolean (*MemoryMonitorCallbackFunc) (GMemoryMonitorPsi            *monitor,

                                               GMemoryMonitorLowMemoryLevel  level_type,

                                               void                         *user_data);

#define G_MEMORY_MONITOR_PSI_GET_INITABLE_IFACE(o) (G_TYPE_INSTANCE_GET_INTERFACE ((o), G_TYPE_INITABLE, GInitable))

static void g_memory_monitor_psi_iface_init (GMemoryMonitorInterface *iface);

static void g_memory_monitor_psi_initable_iface_init (GInitableIface *iface);

struct _GMemoryMonitorPsi

{

  GMemoryMonitorBase parent_instance;

  GMainContext *worker;  /* (unowned) */

  GSource *triggers[G_MEMORY_MONITOR_LOW_MEMORY_LEVEL_COUNT];  /* (owned) (nullable) */

  char *cg_path;

  char *proc_path;

  gboolean proc_override;

};

G_DEFINE_TYPE_WITH_CODE (GMemoryMonitorPsi, g_memory_monitor_psi, G_TYPE_MEMORY_MONITOR_BASE,

                         G_IMPLEMENT_INTERFACE (G_TYPE_INITABLE,

                                                g_memory_monitor_psi_initable_iface_init)

                         G_IMPLEMENT_INTERFACE (G_TYPE_MEMORY_MONITOR,

                                                g_memory_monitor_psi_iface_init)

                         _g_io_modules_ensure_extension_points_registered ();

                         g_io_extension_point_implement (G_MEMORY_MONITOR_EXTENSION_POINT_NAME,

                                                         g_define_type_id,

                                                         "psi",

                                                         20))

static void

g_memory_monitor_psi_init (GMemoryMonitorPsi *psi)

{

}

static void

g_memory_monitor_psi_set_property (GObject      *object,

                                    guint         prop_id,

                                    const GValue *value,

                                    GParamSpec   *pspec)

{

  GMemoryMonitorPsi *monitor = G_MEMORY_MONITOR_PSI (object);

  switch ((GMemoryMonitorPsiProperty) prop_id)

    {

    case PROP_PROC_PATH:

      /* Construct only */

      g_assert (monitor->proc_path == NULL);

      monitor->proc_path = g_value_dup_string (value);

      if (monitor->proc_path != NULL)

        monitor->proc_override = TRUE;

      break;

    default:

      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);

      break;

    }

}

static void

g_memory_monitor_psi_get_property (GObject    *object,

                                   guint       prop_id,

                                   GValue     *value,

                                   GParamSpec *pspec)

{

  GMemoryMonitorPsi *monitor = G_MEMORY_MONITOR_PSI (object);

  switch ((GMemoryMonitorPsiProperty) prop_id)

    {

    case PROP_PROC_PATH:

      g_value_set_string (value, monitor->proc_override ? monitor->proc_path : NULL);

      break;

    default:

      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);

      break;

    }

}

static gboolean

g_memory_monitor_low_trigger_cb (GMemoryMonitorPsi            *monitor,

                                 GMemoryMonitorLowMemoryLevel  level_type,

                                 void                         *user_data)

{

  gdouble mem_ratio;

  /* 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 free ratio > 0.5, don't signal */

  if (mem_ratio < 0.0)

    return G_SOURCE_REMOVE;

  else if (mem_ratio > 0.5)

    return G_SOURCE_CONTINUE;

  g_memory_monitor_base_send_event_to_user (G_MEMORY_MONITOR_BASE (monitor), level_type);

  return G_SOURCE_CONTINUE;

}

static gboolean

event_check (GSource *source)

{

  MemoryMonitorSource *ev_source = (MemoryMonitorSource *) source;

  if (ev_source->pollfd->revents)

    return G_SOURCE_CONTINUE;

  return G_SOURCE_REMOVE;

}

static gboolean

event_dispatch (GSource     *source,

                GSourceFunc  callback,

                gpointer     user_data)

{

  MemoryMonitorSource *ev_source = (MemoryMonitorSource *) source;

  GMemoryMonitorPsi *monitor = NULL;

  monitor = g_weak_ref_get (&ev_source->monitor_weak);

  if (monitor == NULL)

    return G_SOURCE_REMOVE;

  if (monitor->proc_override)

    {

      if (!(g_source_query_unix_fd (source, ev_source->pollfd) & G_IO_IN))

        {

          g_object_unref (monitor);

          return G_SOURCE_CONTINUE;

        }

    }

  else

    {

      if (!(g_source_query_unix_fd (source, ev_source->pollfd) & G_IO_PRI))

        {

          g_object_unref (monitor);

          return G_SOURCE_CONTINUE;

        }

    }

  if (callback)

    ((MemoryMonitorCallbackFunc) callback) (monitor, ev_source->level_type, user_data);

  g_object_unref (monitor);

  return G_SOURCE_CONTINUE;

}

static void

event_finalize (GSource *source)

{

  MemoryMonitorSource *ev_source = (MemoryMonitorSource *) source;

  g_weak_ref_clear (&ev_source->monitor_weak);

}

static GSourceFuncs memory_monitor_event_funcs = {

  .check = event_check,

  .dispatch = event_dispatch,

  .finalize = event_finalize,

};

static GSource *

g_memory_monitor_create_source (GMemoryMonitorPsi            *monitor,

                                int                           fd,

                                GMemoryMonitorLowMemoryLevel  level_type,

                                gboolean                      is_path_override)

{

  MemoryMonitorSource *source;

  source = (MemoryMonitorSource *) g_source_new (&memory_monitor_event_funcs, sizeof (MemoryMonitorSource));

  if (is_path_override)

    source->pollfd = g_source_add_unix_fd ((GSource *) source, fd, G_IO_IN | G_IO_ERR);

  else

    source->pollfd = g_source_add_unix_fd ((GSource *) source, fd, G_IO_PRI | G_IO_ERR);

  source->level_type = level_type;

  g_weak_ref_init (&source->monitor_weak, monitor);

  return (GSource *) source;

}

static gboolean

g_memory_monitor_psi_calculate_mem_pressure_path (GMemoryMonitorPsi  *monitor,

                                                  GError            **error)

{

  pid_t pid;

  gchar *path_read = NULL;

  gchar *replacement = NULL;

  GRegex *regex = NULL;

  if (!monitor->proc_override)

    {

      pid = getpid ();

      monitor->proc_path = g_strdup_printf ("/proc/%d/cgroup", pid);

    }

  if (!g_file_get_contents (monitor->proc_path, &path_read, NULL, error))

    {

      g_free (path_read);

      return FALSE;

    }

  /* cgroupv2 is only supportted and the format is shown as follows:

   * ex: 0::/user.slice/user-0.slice/session-c3.scope */

  regex = g_regex_new ("^0::", G_REGEX_DEFAULT, G_REGEX_MATCH_DEFAULT, error);

  if (!g_regex_match (regex, path_read, G_REGEX_MATCH_DEFAULT, NULL))

    {

      g_debug ("Unsupported cgroup path information.");

      g_free (path_read);

      g_regex_unref (regex);

      return FALSE;

    }

  /* drop "0::" */

  replacement = g_regex_replace (regex, path_read,

                                 -1, 0,

                                 "", G_REGEX_MATCH_DEFAULT, error);

  if (replacement == NULL)

    {

      g_debug ("Unsupported cgroup path format.");

      g_free (path_read);

      g_regex_unref (regex);

      return FALSE;

    }

  replacement = g_strstrip (replacement);

  if (monitor->proc_override)

    {

      monitor->cg_path = g_steal_pointer (&replacement);

      g_free (path_read);

      g_regex_unref (regex);

      return TRUE;

    }

  monitor->cg_path = g_build_filename ("/sys/fs/cgroup", replacement, "memory.pressure", NULL);

  g_debug ("cgroup path is %s", monitor->cg_path);

  g_free (path_read);

  g_free (replacement);

  g_regex_unref (regex);

  return g_file_test (monitor->cg_path, G_FILE_TEST_EXISTS);

}

static GSource *

g_memory_monitor_psi_setup_trigger (GMemoryMonitorPsi             *monitor,

                                    GMemoryMonitorLowMemoryLevel   level_type,

                                    int                            threshold_us,

                                    int                            window_us,

                                    GError                       **error)

{

  GSource *source;

  int fd;

  int ret;

  size_t wlen;

  gchar *trigger = NULL;

  fd = g_open (monitor->cg_path, O_RDWR | O_NONBLOCK | O_CLOEXEC);

  if (fd < 0)

    {

      int errsv = errno;

      g_debug ("Error on opening %s: %s", monitor->cg_path, g_strerror (errsv));

      g_set_error (error, G_IO_ERROR, g_io_error_from_errno (errsv),

                   "Error on opening ‘%s’: %s", monitor->cg_path, g_strerror (errsv));

      return NULL;

    }

  /* The kernel PSI [1] trigger format is:

   * <some|full> <stall amount in us> <time window in us>

   * The “some” indicates the share of time in which at least some tasks are stalled on a given resource.

   * The “full” indicates the share of time in which all non-idle tasks are stalled on a given resource simultaneously.

   * "stall amount in us": The total stall time in us.

   * "time window in us": The specific time window in us.

   * e.g. writing "some 150000 1000000" would add 150ms threshold for partial memory stall measured within 1sec time window

   *

   * [1] https://docs.kernel.org/accounting/psi.html

   */

  trigger = g_strdup_printf ("%s %d %d",

                             (triggers[level_type].trigger_type == MEMORY_PRESSURE_MONITOR_TRIGGER_SOME) ? "some" : "full",

                             threshold_us,

                             window_us);

  errno = 0;

  wlen = strlen (trigger) + 1;

  while (wlen > 0)

    {

      int errsv;

      g_debug ("Write trigger %s", trigger);

      ret = write (fd, trigger, wlen);

      errsv = errno;

      if (ret < 0)

        {

          if (errsv == EINTR)

            {

              /* interrupted by signal, retry */

              continue;

            }

          else

            {

              g_set_error (error,

                           G_IO_ERROR, G_IO_ERROR_FAILED,

                           "Error on setting PSI configurations: %s",

                           g_strerror (errsv));

              g_free (trigger);

              close (fd);

              return NULL;

            }

        }

      wlen -= ret;

    }

  g_free (trigger);

  source = g_memory_monitor_create_source (monitor, fd, level_type, monitor->proc_override);

  g_source_set_callback (source, G_SOURCE_FUNC (g_memory_monitor_low_trigger_cb), NULL, NULL);

  return g_steal_pointer (&source);

}

static gboolean

g_memory_monitor_setup_psi (GMemoryMonitorPsi  *monitor,

                            GError            **error)

{

  if (!g_memory_monitor_psi_calculate_mem_pressure_path (monitor, error))

    return FALSE;

  for (size_t i = 0; i < G_N_ELEMENTS (triggers); i++)

    {

      /* the user defined PSI is estimated per second and the unit is in micro second(us). */

      monitor->triggers[i] = g_memory_monitor_psi_setup_trigger (monitor,

                                                                 i,

                                                                 triggers[i].threshold_ms * 1000,

                                                                 PSI_WINDOW_SEC * 1000 * 1000,

                                                                 error);

      if (monitor->triggers[i] == NULL)

        return FALSE;

    }

  return TRUE;

}

static gboolean

g_memory_monitor_psi_initable_init (GInitable     *initable,

                                    GCancellable  *cancellable,

                                    GError       **error)

{

  GMemoryMonitorPsi *monitor = G_MEMORY_MONITOR_PSI (initable);

  monitor->worker = GLIB_PRIVATE_CALL (g_get_worker_context) ();

  if (g_memory_monitor_setup_psi (monitor, error))

    {

      for (size_t i = 0; i < G_N_ELEMENTS (monitor->triggers); i++)

        {

          g_source_attach (monitor->triggers[i], monitor->worker);

        }

    }

  else

    {

      g_debug ("PSI is not supported.");

      g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED, "PSI is not supported.");

      return FALSE;

    }

  return TRUE;

}

static void

g_memory_monitor_psi_finalize (GObject *object)

{

  GMemoryMonitorPsi *monitor = G_MEMORY_MONITOR_PSI (object);

  g_free (monitor->cg_path);

  g_free (monitor->proc_path);

  for (size_t i = 0; i < G_N_ELEMENTS (monitor->triggers); i++)

    {

      g_source_destroy (monitor->triggers[i]);

      g_source_unref (monitor->triggers[i]);

    }

  G_OBJECT_CLASS (g_memory_monitor_psi_parent_class)->finalize (object);

}

static void

g_memory_monitor_psi_class_init (GMemoryMonitorPsiClass *klass)

{

  GObjectClass *object_class = G_OBJECT_CLASS (klass);

  object_class->set_property = g_memory_monitor_psi_set_property;

  object_class->get_property = g_memory_monitor_psi_get_property;

  object_class->finalize = g_memory_monitor_psi_finalize;

  /**

   * GMemoryMonitorPsi:proc-path: (nullable)

   *

   * Kernel PSI path to use, if not the default.

   *

   * This is typically only used for test purposes.

   *

   * Since: 2.86

   */

  g_object_class_install_property (object_class,

                                   PROP_PROC_PATH,

                                   g_param_spec_string ("proc-path", NULL, NULL,

                                                        NULL,

                                                        G_PARAM_READWRITE |

                                                        G_PARAM_CONSTRUCT_ONLY |

                                                        G_PARAM_STATIC_STRINGS));

}

static void

g_memory_monitor_psi_iface_init (GMemoryMonitorInterface *monitor_iface)

{

}

static void

g_memory_monitor_psi_initable_iface_init (GInitableIface *iface)

{

  iface->init = g_memory_monitor_psi_initable_init;

}