inotify: rewrite inotify-kernel

Remove the hardwired 1 second event queue logic from inotify-kernel and
replace it with something vastly less complicated.

Events are now reported as soon as is possible instead of after a
delay.

We still must delay IN_MOVED_FROM events in order to look for the
matching IN_MOVED_TO events, and since we want to report events in order
this means that events behind those events can also be delayed.  We
limit ourselves, however:

 - no more than 100 events can be delayed at a time

 - no event can be delayed by more than 10ms

https://bugzilla.gnome.org/show_bug.cgi?id=627285
This commit is contained in:
Ryan Lortie 2015-03-05 21:28:29 -05:00
parent fd8b45eb67
commit 779c809a3d
2 changed files with 205 additions and 499 deletions

View File

@ -1,5 +1,6 @@
/*
Copyright (C) 2005 John McCutchan
Copyright © 2015 Canonical Limited
The Gnome Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
@ -15,8 +16,9 @@
License along with the Gnome Library; see the file COPYING.LIB. If not,
see <http://www.gnu.org/licenses/>.
Authors:.
John McCutchan <john@johnmccutchan.com>
Authors:
Ryan Lortie <desrt@desrt.ca>
John McCutchan <john@johnmccutchan.com>
*/
#include "config.h"
@ -29,229 +31,35 @@
#include <glib.h>
#include "inotify-kernel.h"
#include <sys/inotify.h>
#include <glib/glib-unix.h>
#include "glib-private.h"
/* Timings for pairing MOVED_TO / MOVED_FROM events */
#define PROCESS_EVENTS_TIME 1000 /* 1000 milliseconds (1 hz) */
#define DEFAULT_HOLD_UNTIL_TIME 0 /* 0 millisecond */
#define MOVE_HOLD_UNTIL_TIME 500 /* 500 microseconds or 0.5 milliseconds */
static int inotify_instance_fd = -1;
static GQueue *events_to_process = NULL;
static GQueue *event_queue = NULL;
static GHashTable * cookie_hash = NULL;
static GIOChannel *inotify_read_ioc;
static GPollFD ik_poll_fd;
static gboolean ik_poll_fd_enabled = TRUE;
static void (*user_cb)(ik_event_t *event);
static gboolean ik_read_callback (gpointer user_data);
static gboolean ik_process_eq_callback (gpointer user_data);
static guint32 ik_move_matches = 0;
static guint32 ik_move_misses = 0;
static gboolean process_eq_running = FALSE;
/* Define limits on the maximum amount of time and maximum amount of
* interceding events between FROM/TO that can be merged.
*/
#define MOVE_PAIR_DELAY (10 * G_TIME_SPAN_MILLISECOND)
#define MOVE_PAIR_DISTANCE (100)
/* We use the lock from inotify-helper.c
*
* There are two places that we take this lock
*
* 1) In ik_read_callback
*
* 2) ik_process_eq_callback.
*
* We only have to take it on our read callback.
*
* The rest of locking is taken care of in inotify-helper.c
*/
G_LOCK_EXTERN (inotify_lock);
typedef struct ik_event_internal {
ik_event_t *event;
gboolean seen;
gboolean sent;
GTimeVal hold_until;
struct ik_event_internal *pair;
} ik_event_internal_t;
/* In order to perform non-sleeping inotify event chunking we need
* a custom GSource
*/
static gboolean
ik_source_prepare (GSource *source,
gint *timeout)
{
return FALSE;
}
static gboolean
ik_source_timeout (gpointer data)
{
GSource *source = (GSource *)data;
/* Re-active the PollFD */
g_source_add_poll (source, &ik_poll_fd);
g_source_unref (source);
ik_poll_fd_enabled = TRUE;
return FALSE;
}
#define MAX_PENDING_COUNT 2
#define PENDING_THRESHOLD(qsize) ((qsize) >> 1)
#define PENDING_MARGINAL_COST(p) ((unsigned int)(1 << (p)))
#define MAX_QUEUED_EVENTS 2048
#define AVERAGE_EVENT_SIZE sizeof (struct inotify_event) + 16
#define TIMEOUT_MILLISECONDS 10
static gboolean
ik_source_check (GSource *source)
{
static int prev_pending = 0, pending_count = 0;
/* We already disabled the PollFD or
* nothing to be read from inotify */
if (!ik_poll_fd_enabled || !(ik_poll_fd.revents & G_IO_IN))
return FALSE;
if (pending_count < MAX_PENDING_COUNT)
{
GSource *timeout_source;
unsigned int pending;
if (ioctl (inotify_instance_fd, FIONREAD, &pending) == -1)
goto do_read;
pending /= AVERAGE_EVENT_SIZE;
/* Don't wait if the number of pending events is too close
* to the maximum queue size.
*/
if (pending > PENDING_THRESHOLD (MAX_QUEUED_EVENTS))
goto do_read;
/* With each successive iteration, the minimum rate for
* further sleep doubles.
*/
if (pending-prev_pending < PENDING_MARGINAL_COST (pending_count))
goto do_read;
prev_pending = pending;
pending_count++;
/* We are going to wait to read the events: */
/* Remove the PollFD from the source */
g_source_remove_poll (source, &ik_poll_fd);
/* To avoid threading issues we need to flag that we've done that */
ik_poll_fd_enabled = FALSE;
/* Set a timeout to re-add the PollFD to the source */
g_source_ref (source);
timeout_source = g_timeout_source_new (TIMEOUT_MILLISECONDS);
g_source_set_callback (timeout_source, ik_source_timeout, source, NULL);
g_source_attach (timeout_source, GLIB_PRIVATE_CALL (g_get_worker_context) ());
g_source_unref (timeout_source);
return FALSE;
}
do_read:
/* We are ready to read events from inotify */
prev_pending = 0;
pending_count = 0;
return TRUE;
}
static gboolean
ik_source_dispatch (GSource *source,
GSourceFunc callback,
gpointer user_data)
{
if (callback)
return callback (user_data);
return TRUE;
}
static GSourceFuncs ik_source_funcs =
{
ik_source_prepare,
ik_source_check,
ik_source_dispatch,
NULL
};
gboolean _ik_startup (void (*cb)(ik_event_t *event))
{
static gboolean initialized = FALSE;
GSource *source;
user_cb = cb;
/* Ignore multi-calls */
if (initialized)
return inotify_instance_fd >= 0;
initialized = TRUE;
inotify_instance_fd = inotify_init1 (IN_CLOEXEC);
if (inotify_instance_fd < 0)
inotify_instance_fd = inotify_init ();
if (inotify_instance_fd < 0)
return FALSE;
inotify_read_ioc = g_io_channel_unix_new (inotify_instance_fd);
ik_poll_fd.fd = inotify_instance_fd;
ik_poll_fd.events = G_IO_IN | G_IO_HUP | G_IO_ERR;
g_io_channel_set_encoding (inotify_read_ioc, NULL, NULL);
g_io_channel_set_flags (inotify_read_ioc, G_IO_FLAG_NONBLOCK, NULL);
source = g_source_new (&ik_source_funcs, sizeof (GSource));
g_source_set_name (source, "GIO Inotify");
g_source_add_poll (source, &ik_poll_fd);
g_source_set_callback (source, ik_read_callback, NULL, NULL);
g_source_attach (source, GLIB_PRIVATE_CALL (g_get_worker_context) ());
g_source_unref (source);
cookie_hash = g_hash_table_new (g_direct_hash, g_direct_equal);
event_queue = g_queue_new ();
events_to_process = g_queue_new ();
return TRUE;
}
static ik_event_internal_t *
ik_event_internal_new (ik_event_t *event)
{
ik_event_internal_t *internal_event = g_new0 (ik_event_internal_t, 1);
GTimeVal tv;
g_assert (event);
g_get_current_time (&tv);
g_time_val_add (&tv, DEFAULT_HOLD_UNTIL_TIME);
internal_event->event = event;
internal_event->hold_until = tv;
return internal_event;
}
static ik_event_t *
ik_event_new (char *buffer)
ik_event_new (struct inotify_event *kevent,
gint64 now)
{
struct inotify_event *kevent = (struct inotify_event *)buffer;
ik_event_t *event = g_new0 (ik_event_t, 1);
g_assert (buffer);
event->wd = kevent->wd;
event->mask = kevent->mask;
event->cookie = kevent->cookie;
event->len = kevent->len;
event->timestamp = now;
if (event->len)
event->name = g_strdup (kevent->name);
else
@ -265,10 +73,184 @@ _ik_event_free (ik_event_t *event)
{
if (event->pair)
_ik_event_free (event->pair);
g_free (event->name);
g_free (event);
}
typedef struct
{
GSource source;
gpointer fd_tag;
GQueue queue;
gint fd;
} InotifyKernelSource;
static InotifyKernelSource *inotify_source;
static gint64
ik_source_get_ready_time (InotifyKernelSource *iks)
{
ik_event_t *head;
head = g_queue_peek_head (&iks->queue);
/* nothing in the queue: not ready */
if (!head)
return -1;
/* if it's not an unpaired move, it is ready now */
if (~head->mask & IN_MOVED_FROM || head->pair)
return 0;
/* if the queue is too long then it's ready now */
if (iks->queue.length > MOVE_PAIR_DISTANCE)
return 0;
/* otherwise, it's ready after the delay */
return head->timestamp + MOVE_PAIR_DELAY;
}
static gboolean
ik_source_can_dispatch_now (InotifyKernelSource *iks,
gint64 now)
{
gint64 ready_time;
ready_time = ik_source_get_ready_time (iks);
return 0 <= ready_time && ready_time <= now;
}
static void
ik_source_try_to_pair_head (InotifyKernelSource *iks)
{
ik_event_t *head;
GList *node;
node = g_queue_peek_head_link (&iks->queue);
if (!node)
return;
head = node->data;
/* we should only be here if... */
g_assert (head->mask & IN_MOVED_FROM && !head->pair);
while ((node = node->next))
{
ik_event_t *candidate = node->data;
if (candidate->cookie == head->cookie && candidate->mask & IN_MOVED_TO)
{
g_queue_remove (&iks->queue, candidate);
candidate->is_second_in_pair = TRUE;
head->pair = candidate;
return;
}
}
}
static gboolean
ik_source_dispatch (GSource *source,
GSourceFunc func,
gpointer user_data)
{
InotifyKernelSource *iks = (InotifyKernelSource *) source;
void (*user_callback) (ik_event_t *event) = (void *) func;
gint64 now = g_source_get_time (source);
now = g_source_get_time (source);
/* Only try to fill the queue if we don't already have work to do. */
if (!ik_source_can_dispatch_now (iks, now) &&
g_source_query_unix_fd (source, iks->fd_tag))
{
gchar buffer[sizeof(struct inotify_event) + NAME_MAX + 1];
gssize result;
gssize offset;
result = read (iks->fd, buffer, sizeof buffer);
if (result < 0)
g_error ("inotify error: %s\n", g_strerror (errno));
else if (result == 0)
g_error ("inotify unexpectedly hit eof");
offset = 0;
while (offset < result)
{
struct inotify_event *event = (struct inotify_event *) (buffer + offset);
g_queue_push_tail (&iks->queue, ik_event_new (event, now));
offset += sizeof (struct inotify_event) + event->len;
}
}
if (!ik_source_can_dispatch_now (iks, now))
ik_source_try_to_pair_head (iks);
if (ik_source_can_dispatch_now (iks, now))
{
ik_event_t *event;
/* callback will free the event */
event = g_queue_pop_head (&iks->queue);
G_LOCK (inotify_lock);
(* user_callback) (event);
G_UNLOCK (inotify_lock);
}
g_source_set_ready_time (source, ik_source_get_ready_time (iks));
return TRUE;
}
static InotifyKernelSource *
ik_source_new (void (* callback) (ik_event_t *event))
{
static GSourceFuncs source_funcs = {
NULL, NULL,
ik_source_dispatch
/* should have a finalize, but it will never happen */
};
InotifyKernelSource *iks;
GSource *source;
source = g_source_new (&source_funcs, sizeof (InotifyKernelSource));
iks = (InotifyKernelSource *) source;
g_source_set_name (source, "inotify kernel source");
iks->fd = inotify_init1 (IN_CLOEXEC);
if (iks->fd < 0)
iks->fd = inotify_init ();
if (iks->fd >= 0)
iks->fd_tag = g_source_add_unix_fd (source, iks->fd, G_IO_IN);
g_source_set_callback (source, (GSourceFunc) callback, NULL, NULL);
g_source_attach (source, GLIB_PRIVATE_CALL (g_get_worker_context) ());
return iks;
}
gboolean
_ik_startup (void (*cb)(ik_event_t *event))
{
if (g_once_init_enter (&inotify_source))
g_once_init_leave (&inotify_source, ik_source_new (cb));
return inotify_source->fd >= 0;
}
gint32
_ik_watch (const char *path,
guint32 mask,
@ -277,16 +259,16 @@ _ik_watch (const char *path,
gint32 wd = -1;
g_assert (path != NULL);
g_assert (inotify_instance_fd >= 0);
g_assert (inotify_source && inotify_source->fd >= 0);
wd = inotify_add_watch (inotify_instance_fd, path, mask);
wd = inotify_add_watch (inotify_source->fd, path, mask);
if (wd < 0)
{
int e = errno;
/* FIXME: debug msg failed to add watch */
if (err)
*err = e;
*err = e;
return wd;
}
@ -299,9 +281,9 @@ _ik_ignore (const char *path,
gint32 wd)
{
g_assert (wd >= 0);
g_assert (inotify_instance_fd >= 0);
g_assert (inotify_source && inotify_source->fd >= 0);
if (inotify_rm_watch (inotify_instance_fd, wd) < 0)
if (inotify_rm_watch (inotify_source->fd, wd) < 0)
{
/* int e = errno; */
/* failed to rm watch */
@ -310,280 +292,3 @@ _ik_ignore (const char *path,
return 0;
}
static void
ik_read_events (gsize *buffer_size_out,
gchar **buffer_out)
{
static gchar *buffer = NULL;
static gsize buffer_size;
/* Initialize the buffer on our first call */
if (buffer == NULL)
{
buffer_size = AVERAGE_EVENT_SIZE;
buffer_size *= MAX_QUEUED_EVENTS;
buffer = g_malloc (buffer_size);
}
*buffer_size_out = 0;
*buffer_out = NULL;
memset (buffer, 0, buffer_size);
if (g_io_channel_read_chars (inotify_read_ioc, (char *)buffer, buffer_size, buffer_size_out, NULL) != G_IO_STATUS_NORMAL) {
/* error reading */
}
*buffer_out = buffer;
}
static gboolean
ik_read_callback (gpointer user_data)
{
gchar *buffer;
gsize buffer_size, buffer_i, events;
G_LOCK (inotify_lock);
ik_read_events (&buffer_size, &buffer);
buffer_i = 0;
events = 0;
while (buffer_i < buffer_size)
{
struct inotify_event *event;
gsize event_size;
event = (struct inotify_event *)&buffer[buffer_i];
event_size = sizeof(struct inotify_event) + event->len;
g_queue_push_tail (events_to_process, ik_event_internal_new (ik_event_new (&buffer[buffer_i])));
buffer_i += event_size;
events++;
}
/* If the event process callback is off, turn it back on */
if (!process_eq_running && events)
{
GSource *timeout_source;
process_eq_running = TRUE;
timeout_source = g_timeout_source_new (PROCESS_EVENTS_TIME);
g_source_set_callback (timeout_source, ik_process_eq_callback, NULL, NULL);
g_source_attach (timeout_source, GLIB_PRIVATE_CALL (g_get_worker_context ()));
g_source_unref (timeout_source);
}
G_UNLOCK (inotify_lock);
return TRUE;
}
static gboolean
g_timeval_lt (GTimeVal *val1,
GTimeVal *val2)
{
if (val1->tv_sec < val2->tv_sec)
return TRUE;
if (val1->tv_sec > val2->tv_sec)
return FALSE;
/* val1->tv_sec == val2->tv_sec */
if (val1->tv_usec < val2->tv_usec)
return TRUE;
return FALSE;
}
static gboolean
g_timeval_le (GTimeVal *val1,
GTimeVal *val2)
{
if (val1->tv_sec < val2->tv_sec)
return TRUE;
if (val1->tv_sec > val2->tv_sec)
return FALSE;
/* val1->tv_sec == val2->tv_sec */
if (val1->tv_usec <= val2->tv_usec)
return TRUE;
return FALSE;
}
static void
ik_pair_events (ik_event_internal_t *event1,
ik_event_internal_t *event2)
{
g_assert (event1 && event2);
/* We should only be pairing events that have the same cookie */
g_assert (event1->event->cookie == event2->event->cookie);
/* We shouldn't pair an event that already is paired */
g_assert (event1->pair == NULL && event2->pair == NULL);
/* Pair the internal structures and the ik_event_t structures */
event1->pair = event2;
event1->event->pair = event2->event;
event2->event->is_second_in_pair = TRUE;
if (g_timeval_lt (&event1->hold_until, &event2->hold_until))
event1->hold_until = event2->hold_until;
event2->hold_until = event1->hold_until;
}
static void
ik_event_add_microseconds (ik_event_internal_t *event,
glong ms)
{
g_assert (event);
g_time_val_add (&event->hold_until, ms);
}
static gboolean
ik_event_ready (ik_event_internal_t *event)
{
GTimeVal tv;
g_assert (event);
g_get_current_time (&tv);
/* An event is ready if,
*
* it has no cookie -- there is nothing to be gained by holding it
* or, it is already paired -- we don't need to hold it anymore
* or, we have held it long enough
*/
return
event->event->cookie == 0 ||
event->pair != NULL ||
g_timeval_le (&event->hold_until, &tv);
}
static void
ik_pair_moves (gpointer data,
gpointer user_data)
{
ik_event_internal_t *event = (ik_event_internal_t *)data;
if (event->seen == TRUE || event->sent == TRUE)
return;
if (event->event->cookie != 0)
{
/* When we get a MOVED_FROM event we delay sending the event by
* MOVE_HOLD_UNTIL_TIME microseconds. We need to do this because a
* MOVED_TO pair _might_ be coming in the near future */
if (event->event->mask & IN_MOVED_FROM)
{
g_hash_table_insert (cookie_hash, GINT_TO_POINTER (event->event->cookie), event);
/* because we don't deliver move events there is no point in waiting for the match right now. */
ik_event_add_microseconds (event, MOVE_HOLD_UNTIL_TIME);
}
else if (event->event->mask & IN_MOVED_TO)
{
/* We need to check if we are waiting for this MOVED_TO events cookie to pair it with
* a MOVED_FROM */
ik_event_internal_t *match = NULL;
match = g_hash_table_lookup (cookie_hash, GINT_TO_POINTER (event->event->cookie));
if (match)
{
g_hash_table_remove (cookie_hash, GINT_TO_POINTER (event->event->cookie));
ik_pair_events (match, event);
}
}
}
event->seen = TRUE;
}
static void
ik_process_events (void)
{
g_queue_foreach (events_to_process, ik_pair_moves, NULL);
while (!g_queue_is_empty (events_to_process))
{
ik_event_internal_t *event = g_queue_peek_head (events_to_process);
/* This must have been sent as part of a MOVED_TO/MOVED_FROM */
if (event->sent)
{
/* Pop event */
g_queue_pop_head (events_to_process);
/* Free the internal event structure */
g_free (event);
continue;
}
/* The event isn't ready yet */
if (!ik_event_ready (event))
break;
/* Pop it */
event = g_queue_pop_head (events_to_process);
/* Check if this is a MOVED_FROM that is also sitting in the cookie_hash */
if (event->event->cookie && event->pair == NULL &&
g_hash_table_lookup (cookie_hash, GINT_TO_POINTER (event->event->cookie)))
g_hash_table_remove (cookie_hash, GINT_TO_POINTER (event->event->cookie));
if (event->pair)
{
/* We send out paired MOVED_FROM/MOVED_TO events in the same event buffer */
/* g_assert (event->event->mask == IN_MOVED_FROM && event->pair->event->mask == IN_MOVED_TO); */
/* Copy the paired data */
event->pair->sent = TRUE;
event->sent = TRUE;
ik_move_matches++;
}
else if (event->event->cookie)
{
/* If we couldn't pair a MOVED_FROM and MOVED_TO together, we change
* the event masks */
/* Changeing MOVED_FROM to DELETE and MOVED_TO to create lets us make
* the gaurantee that you will never see a non-matched MOVE event */
event->event->original_mask = event->event->mask;
if (event->event->mask & IN_MOVED_FROM)
{
event->event->mask = IN_DELETE|(event->event->mask & IN_ISDIR);
ik_move_misses++; /* not super accurate, if we aren't watching the destination it still counts as a miss */
}
if (event->event->mask & IN_MOVED_TO)
event->event->mask = IN_CREATE|(event->event->mask & IN_ISDIR);
}
/* Push the ik_event_t onto the event queue */
g_queue_push_tail (event_queue, event->event);
/* Free the internal event structure */
g_free (event);
}
}
static gboolean
ik_process_eq_callback (gpointer user_data)
{
gboolean res;
/* Try and move as many events to the event queue */
G_LOCK (inotify_lock);
ik_process_events ();
while (!g_queue_is_empty (event_queue))
{
ik_event_t *event = g_queue_pop_head (event_queue);
user_cb (event);
}
res = TRUE;
if (g_queue_get_length (events_to_process) == 0)
{
process_eq_running = FALSE;
res = FALSE;
}
G_UNLOCK (inotify_lock);
return res;
}

View File

@ -37,6 +37,7 @@ typedef struct ik_event_s {
* then event1->pair == event2 and event2->pair == NULL.
* It will result also in event1->pair->is_second_in_pair == TRUE */
struct ik_event_s *pair;
gint64 timestamp; /* monotonic time that this was created */
} ik_event_t;
gboolean _ik_startup (void (*cb) (ik_event_t *event));