command: add settings to enable async io

There are config settings to enable aio, and to configure
the concurrency and read size.

5 files changed, 49 insertions, 0 deletions

diff --git a/daemons/clvmd/lvm-functions.c b/daemons/clvmd/lvm-functions.c
index e872fbe49..84b3b5587 100644
--- a/daemons/clvmd/lvm-functions.c
+++ b/daemons/clvmd/lvm-functions.c
@@ -661,6 +661,7 @@ int do_refresh_cache(void)
 		return -1;
 	}
 
+	cmd->use_aio = 0;
 	init_full_scan_done(0);
 	init_ignore_suspended_devices(1);
 	lvmcache_force_next_label_scan();
@@ -920,6 +921,7 @@ int init_clvm(struct dm_hash_table *excl_uuid)
 	/* Check lvm.conf is setup for cluster-LVM */
 	check_config();
 	init_ignore_suspended_devices(1);
+	cmd->use_aio = 0;
 
 	/* Trap log messages so we can pass them back to the user */
 	init_log_fn(lvm2_log_fn);
diff --git a/lib/commands/toolcontext.c b/lib/commands/toolcontext.c
index e742df5e0..9f86c13e4 100644
--- a/lib/commands/toolcontext.c
+++ b/lib/commands/toolcontext.c
@@ -542,6 +542,7 @@ static int _process_config(struct cmd_context *cmd)
 	const struct dm_config_value *cv;
 	int64_t pv_min_kb;
 	int udev_disabled = 0;
+	int scan_size_kb;
 	char sysfs_dir[PATH_MAX];
 
 	if (!_check_config(cmd))
@@ -625,6 +626,29 @@ static int _process_config(struct cmd_context *cmd)
 	cmd->default_settings.udev_sync = udev_disabled ? 0 :
 		find_config_tree_bool(cmd, activation_udev_sync_CFG, NULL);
 
+#ifdef AIO_SUPPORT
+	cmd->use_aio = find_config_tree_bool(cmd, devices_scan_async_CFG, NULL);
+#else
+	cmd->use_aio = 0;
+	if (find_config_tree_bool(cmd, devices_scan_async_CFG, NULL))
+		log_verbose("Ignoring scan_async, no async I/O support.");
+#endif
+	scan_size_kb = find_config_tree_int(cmd, devices_scan_size_CFG, NULL);
+
+	if (!scan_size_kb || (scan_size_kb < 0) || (scan_size_kb % 4)) {
+		log_warn("WARNING: Ignoring invalid scan_size %d KB, using default %u KB.",
+			 scan_size_kb, DEFAULT_SCAN_SIZE_KB);
+		log_warn("scan_size has units of KB and must be a multiple of 4 KB.");
+		scan_size_kb = DEFAULT_SCAN_SIZE_KB;
+	}
+
+	cmd->default_settings.scan_size_kb = scan_size_kb;
+
+	if (cmd->use_aio)
+		log_debug("Using async io with scan_size %u KB.", scan_size_kb);
+	else
+		log_debug("Using sync io with scan_size %u KB.", scan_size_kb);
+
 	/*
 	 * Set udev_fallback lazily on first use since it requires
 	 * checking DM driver version which is an extra ioctl!
@@ -2226,6 +2250,8 @@ void destroy_toolcontext(struct cmd_context *cmd)
 	    !cmd->filter->dump(cmd->filter, 1))
 		stack;
 
+	label_scan_destroy(cmd);
+
 	archive_exit(cmd);
 	backup_exit(cmd);
 	lvmcache_destroy(cmd, 0, 0);
diff --git a/lib/commands/toolcontext.h b/lib/commands/toolcontext.h
index bf2b25124..10987ee72 100644
--- a/lib/commands/toolcontext.h
+++ b/lib/commands/toolcontext.h
@@ -40,6 +40,7 @@ struct config_info {
 	int udev_sync;
 	int udev_fallback;
 	int cache_vgmetadata;
+	int scan_size_kb;
 	const char *msg_prefix;
 	const char *fmt_name;
 	uint64_t unit_factor;
@@ -164,6 +165,7 @@ struct cmd_context {
 	unsigned vg_notify:1;
 	unsigned lv_notify:1;
 	unsigned pv_notify:1;
+	unsigned use_aio:1;
 
 	/*
 	 * Filtering.
diff --git a/lib/config/config_settings.h b/lib/config/config_settings.h
index 7d800b3d8..33ebee9d9 100644
--- a/lib/config/config_settings.h
+++ b/lib/config/config_settings.h
@@ -457,6 +457,23 @@ cfg(devices_allow_changes_with_duplicate_pvs_CFG, "allow_changes_with_duplicate_
 	"Enabling this setting allows the VG to be used as usual even with\n"
 	"uncertain devices.\n")
 
+cfg(devices_scan_async_CFG, "scan_async", devices_CFG_SECTION, CFG_DEFAULT_COMMENTED, CFG_TYPE_BOOL, DEFAULT_SCAN_ASYNC, vsn(2, 2, 173), NULL, 0, NULL,
+	"Use async I/O to read headers and metadata from disks in parallel.\n")
+
+cfg(devices_scan_size_CFG, "scan_size", devices_CFG_SECTION, CFG_DEFAULT_COMMENTED, CFG_TYPE_INT, DEFAULT_SCAN_SIZE_KB, vsn(2, 2, 173), NULL, 0, NULL,
+	"Number of KiB to read from each disk when scanning disks.\n"
+	"The initial scan size is intended to cover all the headers\n"
+	"and metadata that LVM places at the start of each disk so\n"
+	"that a single read operation can retrieve them all.\n"
+	"Any headers or metadata that lie beyond this size require\n"
+	"an additional disk read. Must be a multiple of 4KiB.\n")
+
+cfg(devices_async_events_CFG, "async_events", devices_CFG_SECTION, CFG_DEFAULT_COMMENTED, CFG_TYPE_INT, DEFAULT_ASYNC_EVENTS, vsn(2, 2, 173), NULL, 0, NULL,
+	"Max number of concurrent async reads when scanning disks.\n"
+	"Up to this many disks can be read concurrently when scanning\n"
+	"disks with async I/O. This setting may be limited by the system\n"
+	"aio configuration.\n")
+
 cfg_array(allocation_cling_tag_list_CFG, "cling_tag_list", allocation_CFG_SECTION, CFG_DEFAULT_UNDEFINED, CFG_TYPE_STRING, NULL, vsn(2, 2, 77), NULL, 0, NULL,
 	"Advise LVM which PVs to use when searching for new space.\n"
 	"When searching for free space to extend an LV, the 'cling' allocation\n"
diff --git a/lib/config/defaults.h b/lib/config/defaults.h
index 8da8670d1..533aad11a 100644
--- a/lib/config/defaults.h
+++ b/lib/config/defaults.h
@@ -268,5 +268,7 @@
 #define DEFAULT_THIN_POOL_AUTOEXTEND_PERCENT 20
 
 #define DEFAULT_ASYNC_EVENTS 100
+#define DEFAULT_SCAN_ASYNC 1
+#define DEFAULT_SCAN_SIZE_KB 128
 
 #endif				/* _LVM_DEFAULTS_H */