Add idle_threads mount option.

ChangeLog.rst

@@ -53,6 +53,13 @@ libfuse 3.1.1 (2017-08-06)
 
 * Fixed a test failure when /tmp is on btrfs.
 
+* The maximum number of idle worker threads used by `fuse_loop_mt()`
+  is now configurable.
+
+* `fuse_loop_mt()` and `fuse_session_loop_mt()` now take a
+  `struct fuse_loop_config` parameter that supersedes the *clone_fd*
+  parameter.
+
 * Incorporated several patches from the FreeBSD port. libfuse should
   now compile under FreeBSD without the need for patches.
 

configure.ac

@@ -1,4 +1,4 @@
-AC_INIT(fuse, 3.1.1)
+AC_INIT(fuse, 3.2.0)
 AC_PREREQ(2.59d)
 AC_CONFIG_MACRO_DIR([m4])
 AC_CANONICAL_TARGET

include/fuse.h

@@ -964,13 +964,17 @@ void fuse_exit(struct fuse *f);
  * in the callback function of fuse_operations is also thread-safe.
  *
  * @param f the FUSE handle
- * @param clone_fd whether to use separate device fds for each thread
- *                 (may increase performance)
+ * @param config loop configuration
  * @return see fuse_session_loop()
  *
  * See also: fuse_loop()
  */
-int fuse_loop_mt(struct fuse *f, int clone_fd);
+#if FUSE_USE_VERSION < 32
+int fuse_loop_mt_31(struct fuse *f, int clone_fd);
+#define fuse_loop_mt(f, clone_fd) fuse_loop_mt_31(f, clone_fd)
+#else
+int fuse_loop_mt(struct fuse *f, struct fuse_loop_config *config);
+#endif
 
 /**
  * Get the current context

include/fuse_common.h

@@ -22,7 +22,7 @@
 #define FUSE_MAJOR_VERSION 3
 
 /** Minor version of FUSE library interface */
-#define FUSE_MINOR_VERSION 1
+#define FUSE_MINOR_VERSION 2
 
 #define FUSE_MAKE_VERSION(maj, min)  ((maj) * 10 + (min))
 #define FUSE_VERSION FUSE_MAKE_VERSION(FUSE_MAJOR_VERSION, FUSE_MINOR_VERSION)
@@ -79,7 +79,29 @@ struct fuse_file_info {
 	uint32_t poll_events;
 };
 
+/**
+ * Configuration parameters passed to fuse_session_loop_mt() and
+ * fuse_loop_mt().
+ */
+struct fuse_loop_config {
+	/**
+	 * whether to use separate device fds for each thread
+	 * (may increase performance)
+	 */
+	int clone_fd;
 
+	/**
+	 * The maximum number of available worker threads before they
+	 * start to get deleted when they become idle. If not
+	 * specified, the default is 10.
+	 *
+	 * Adjusting this has performance implications; a very small number
+	 * of threads in the pool will cause a lot of thread creation and
+	 * deletion overhead and performance may suffer. When set to 0, a new
+	 * thread will be created to service every operation.
+	 */
+	unsigned int max_idle_threads;
+};
 
 /**************************************************************************
  * Capability bits for 'fuse_conn_info.capable' and 'fuse_conn_info.want' *

include/fuse_lowlevel.h

@@ -1760,6 +1760,7 @@ struct fuse_cmdline_opts {
 	int show_version;
 	int show_help;
 	int clone_fd;
+	unsigned int max_idle_threads;
 };
 
 /**
@@ -1857,11 +1858,15 @@ int fuse_session_loop(struct fuse_session *se);
  * fuse_session_loop().
  *
  * @param se the session
- * @param clone_fd whether to use separate device fds for each thread
- *                 (may increase performance)
+ * @param config session loop configuration 
  * @return see fuse_session_loop()
  */
-int fuse_session_loop_mt(struct fuse_session *se, int clone_fd);
+#if FUSE_USE_VERSION < 32
+int fuse_session_loop_mt_31(struct fuse_session *se, int clone_fd);
+#define fuse_session_loop_mt(se, clone_fd) fuse_session_loop_mt_31(se, clone_fd)
+#else
+int fuse_session_loop_mt(struct fuse_session *se, struct fuse_loop_config *config);
+#endif
 
 /**
  * Flag a session as terminated.

lib/Makefile.am

@@ -1,7 +1,7 @@
 ## Process this file with automake to produce Makefile.in
 
 AM_CPPFLAGS = -I$(top_srcdir)/include -DFUSERMOUNT_DIR=\"$(bindir)\" \
- -D_REENTRANT -DFUSE_USE_VERSION=31
+ -D_REENTRANT -DFUSE_USE_VERSION=32
 
 lib_LTLIBRARIES = libfuse3.la
 

lib/cuse_lowlevel.c

@@ -349,8 +349,12 @@ int cuse_lowlevel_main(int argc, char *argv[], const struct cuse_info *ci,
 	if (se == NULL)
 		return 1;
 
-	if (multithreaded)
-		res = fuse_session_loop_mt(se, 0);
+	if (multithreaded) {
+		struct fuse_loop_config config;
+		config.clone_fd = 0;
+		config.max_idle_threads = 10;
+		res = fuse_session_loop_mt(se, &config);
+	}
 	else
 		res = fuse_session_loop(se);
 

lib/fuse.c

@@ -4382,7 +4382,9 @@ int fuse_loop(struct fuse *f)
 	return fuse_session_loop(f->se);
 }
 
-int fuse_loop_mt(struct fuse *f, int clone_fd)
+int fuse_loop_mt_32(struct fuse *f, struct fuse_loop_config *config);
+FUSE_SYMVER(".symver fuse_loop_mt_32,fuse_loop_mt@@FUSE_3.2");
+int fuse_loop_mt_32(struct fuse *f, struct fuse_loop_config *config)
 {
 	if (f == NULL)
 		return -1;
@@ -4391,11 +4393,21 @@ int fuse_loop_mt(struct fuse *f, int clone_fd)
 	if (res)
 		return -1;
 
-	res = fuse_session_loop_mt(fuse_get_session(f), clone_fd);
+	res = fuse_session_loop_mt(fuse_get_session(f), config);
 	fuse_stop_cleanup_thread(f);
 	return res;
 }
 
+int fuse_loop_mt_31(struct fuse *f, int clone_fd);
+FUSE_SYMVER(".symver fuse_loop_mt_31,fuse_loop_mt@FUSE_3.1");
+int fuse_loop_mt_31(struct fuse *f, int clone_fd)
+{
+	struct fuse_loop_config config;
+	config.clone_fd = clone_fd;
+	config.max_idle_threads = 10;
+	return fuse_loop_mt_32(f, &config);
+}
+
 void fuse_exit(struct fuse *f)
 {
 	fuse_session_exit(f->se);

lib/fuse_loop_mt.c

@@ -48,6 +48,7 @@ struct fuse_mt {
 	int exit;
 	int error;
 	int clone_fd;
+	int max_idle;
 };
 
 static struct fuse_chan *fuse_chan_new(int fd)
@@ -161,7 +162,7 @@ static void *fuse_do_work(void *data)
 		pthread_mutex_lock(&mt->lock);
 		if (!isforget)
 			mt->numavail++;
-		if (mt->numavail > 10) {
+		if (mt->numavail > mt->max_idle) {
 			if (mt->exit) {
 				pthread_mutex_unlock(&mt->lock);
 				return NULL;
@@ -300,18 +301,21 @@ static void fuse_join_worker(struct fuse_mt *mt, struct fuse_worker *w)
 	free(w);
 }
 
-int fuse_session_loop_mt(struct fuse_session *se, int clone_fd)
+int fuse_session_loop_mt_32(struct fuse_session *se, struct fuse_loop_config *config);
+FUSE_SYMVER(".symver fuse_session_loop_mt_32,fuse_session_loop_mt@@FUSE_3.2");
+int fuse_session_loop_mt_32(struct fuse_session *se, struct fuse_loop_config *config)
 {
 	int err;
 	struct fuse_mt mt;
 	struct fuse_worker *w;
 
 	memset(&mt, 0, sizeof(struct fuse_mt));
 	mt.se = se;
-	mt.clone_fd = clone_fd;
+	mt.clone_fd = config->clone_fd;
 	mt.error = 0;
 	mt.numworker = 0;
 	mt.numavail = 0;
+	mt.max_idle = config->max_idle_threads;
 	mt.main.thread_id = pthread_self();
 	mt.main.prev = mt.main.next = &mt.main;
 	sem_init(&mt.finish, 0, 0);
@@ -344,3 +348,13 @@ int fuse_session_loop_mt(struct fuse_session *se, int clone_fd)
 	fuse_session_reset(se);
 	return err;
 }
+
+int fuse_session_loop_mt_31(struct fuse_session *se, int clone_fd);
+FUSE_SYMVER(".symver fuse_session_loop_mt_31,fuse_session_loop_mt@FUSE_3.1");
+int fuse_session_loop_mt_31(struct fuse_session *se, int clone_fd)
+{
+	struct fuse_loop_config config;
+	config.clone_fd = clone_fd;
+	config.max_idle_threads = 10;
+	return fuse_session_loop_mt_32(se, &config);
+}

lib/fuse_versionscript

@@ -139,6 +139,12 @@ FUSE_3.1 {
 		fuse_invalidate_path;
 } FUSE_3.0;
 
+FUSE_3.2 {
+	global:
+		fuse_session_loop_mt_31;
+		fuse_loop_mt_31;
+} FUSE_3.1;
+
 # Local Variables:
 # indent-tabs-mode: t
 # End:

lib/helper.c

@@ -48,6 +48,7 @@ static const struct fuse_opt fuse_helper_opts[] = {
 	FUSE_OPT_KEY("subtype=",	FUSE_OPT_KEY_KEEP),
 #endif
 	FUSE_HELPER_OPT("clone_fd",	clone_fd),
+	FUSE_HELPER_OPT("max_idle_threads=%u", max_idle_threads),
 	FUSE_OPT_END
 };
 
@@ -132,7 +133,9 @@ void fuse_cmdline_help(void)
 	       "    -f                     foreground operation\n"
 	       "    -s                     disable multi-threaded operation\n"
 	       "    -o clone_fd            use separate fuse device fd for each thread\n"
-	       "                           (may improve performance)\n");
+	       "                           (may improve performance)\n"
+	       "    -o max_idle_threads    the maximum number of idle worker threads\n"
+	       "                           allowed (default: 10)\n");
 }
 
 static int fuse_helper_opt_proc(void *data, const char *arg, int key,
@@ -195,6 +198,9 @@ int fuse_parse_cmdline(struct fuse_args *args,
 		       struct fuse_cmdline_opts *opts)
 {
 	memset(opts, 0, sizeof(struct fuse_cmdline_opts));
+
+	opts->max_idle_threads = 10;
+
 	if (fuse_opt_parse(args, opts, fuse_helper_opts,
 			   fuse_helper_opt_proc) == -1)
 		return -1;
@@ -326,8 +332,12 @@ int fuse_main_real(int argc, char *argv[], const struct fuse_operations *op,
 
 	if (opts.singlethread)
 		res = fuse_loop(fuse);
-	else
-		res = fuse_loop_mt(fuse, opts.clone_fd);
+	else {
+		struct fuse_loop_config loop_config;
+		loop_config.clone_fd = opts.clone_fd;
+		loop_config.max_idle_threads = opts.max_idle_threads;
+		res = fuse_loop_mt(fuse, &loop_config);
+	}
 	if (res)
 		res = 1;
 

lib/meson.build

@@ -29,7 +29,7 @@ libfuse = library('fuse3', libfuse_sources, version: meson.project_version(),
                   soversion: '3', include_directories: include_dirs,
                   dependencies: deps, install: true,
                   link_depends: 'fuse_versionscript',
-                  c_args: [ '-DFUSE_USE_VERSION=31',
+                  c_args: [ '-DFUSE_USE_VERSION=32',
                             '-DFUSERMOUNT_DIR="{}"'.format(fusermount_path) ],
                   link_args: ['-Wl,--version-script,' + meson.current_source_dir()
                               + '/fuse_versionscript' ])

meson.build

@@ -1,4 +1,4 @@
-project('libfuse3', 'c', version: '3.1.1',
+project('libfuse3', 'c', version: '3.2.0',
         meson_version: '>= 0.38',
         default_options: [ 'buildtype=debugoptimized' ])