glib/gio/inotify/meson.build
Gleb Popov dae3b8bd15 Introduce a special mode of operating for the inotify GFileMonitor backend
libinotify-kqueue is a library that implements inotify interface in terms of
kqueue/kevent API available on Mac OS and *BSD systems. The original kqueue
backend seems to be a predecessor version of the code that is currently present
in libinotify-kqueue. Under the hood the library implements a sophisticated
filesystem changes detection algorithm that is derived from the glib backend
code.

Updating the native glib kqueue backend requires substantial work, because code
bases have diverged greatly. Another approach is taken, instead. libinotify-kqueue
can serve as a drop-in replacement for Linux inotify API, thus allowing to
reuse the inotify backend code. The compatibility, however, comes at cost, since
the library has to emulate the inotify descriptor via an unix domain socket.
This means that delivering an event involves copying the data into the kernel
and then pulling it back.

The recent libinotify-kqueue release adds a new mode of operation called "direct".
In this mode the socket pipe is replaced with another kqueue that is used to
deliver events via a kevent(EVFILT_USER) call.
Employing the direct mode requires minor changes to the client code compared
to using plain inotify API, but in return it allows for reusing libinotify's
algorithms without a performance penalty. Luckily, all required changes are
consolidated in one file called inotify-kernel.c

This puts us in the best of possible worlds. On one hand we share a lot of code
with glib inotify backend, which is far more thoroughly tested and widely used.
On the other we support a range of non-Linux systems and consolidate the business
logic in one library. I plan to do the same trick for QFileSystemWatcher which
will give us the same behaviour between Gtk and Qt applications.

The glib test suite passes for both old kqueue backend and new libinotify-kqueue
one. However, the AppStream FileMonitor tests are failing with the old backend,
but pass with the new one, so this is still an observable improvement.

Relevant libinotify-kqueue PR: https://github.com/libinotify-kqueue/libinotify-kqueue/pull/19
2024-09-19 09:54:56 +03:00

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Meson

# Copyright 2016 Centricular
# Copyright 2018 Endless Mobile, Inc.
# Copyright 2022 Collabora, Ltd.
# Copyright 2023 Eli Schwartz
# Copyright 2023 Canonical Ltd.
#
# 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/>.
inotify_sources = [
'inotify-kernel.c',
'inotify-sub.c',
'inotify-path.c',
'inotify-missing.c',
'inotify-helper.c',
'ginotifyfilemonitor.c',
]
# necessary for the libinotify-kqueue backend
libinotify_kqueue_dep = dependency('libinotify', required: file_monitor_backend == 'libinotify-kqueue')
inotify_lib = static_library('inotify',
sources : [inotify_sources],
include_directories : [configinc, glibinc],
dependencies : [
gioenumtypes_dep,
libglib_dep,
libgobject_dep,
gmodule_inc_dep,
libinotify_kqueue_dep,
],
gnu_symbol_visibility : 'hidden',
pic : true,
c_args : [gio_c_args, gio_c_args_internal])