diff --git a/src/dns_cache.c b/src/dns_cache.c
index 3e8e80c4ad..9e40e8b416 100644
--- a/src/dns_cache.c
+++ b/src/dns_cache.c
@@ -19,9 +19,11 @@
 #include "dns_cache.h"
 #include "stringutil.h"
 #include "tlog.h"
+#include "util.h"
 #include <errno.h>
 #include <fcntl.h>
 #include <pthread.h>
+#include <stdio.h>
 #include <string.h>
 #include <sys/types.h>
 
@@ -40,6 +42,8 @@ struct dns_cache_head {
 	pthread_mutex_t lock;
 };
 
+typedef int (*dns_cache_read_callback)(struct dns_cache_record *cache_record, struct dns_cache_data *cache_data);
+
 static struct dns_cache_head dns_cache_head;
 
 int dns_cache_init(int size, int enable_inactive, int inactive_list_expired)
@@ -127,7 +131,7 @@ static void _dns_cache_remove(struct dns_cache *dns_cache)
 
 static void _dns_cache_move_inactive(struct dns_cache *dns_cache)
 {
-	list_del_init(&dns_cache->list);
+	list_del(&dns_cache->list);
 	list_add_tail(&dns_cache->list, &dns_cache_head.inactive_list);
 	time(&dns_cache->info.replace_time);
 }
@@ -256,6 +260,24 @@ struct dns_cache_data *dns_cache_new_data_packet(void *packet, size_t packet_len
 	return (struct dns_cache_data *)cache_packet;
 }
 
+static void _dns_cache_insert_sorted(struct dns_cache *dns_cache, struct list_head *head)
+{
+	time_t ttl;
+	struct dns_cache *tmp = NULL;
+
+	/* ascending order */
+	ttl = dns_cache->info.insert_time + dns_cache->info.ttl;
+	list_for_each_entry_reverse(tmp, head, list)
+	{
+		if ((tmp->info.insert_time + tmp->info.ttl) <= ttl) {
+			list_add(&dns_cache->list, &tmp->list);
+			return;
+		}
+	}
+
+	list_add(&dns_cache->list, head);
+}
+
 static int _dns_cache_replace(struct dns_cache_key *cache_key, int ttl, int speed, int no_inactive, int inactive,
 							  struct dns_cache_data *cache_data)
 {
@@ -288,12 +310,12 @@ static int _dns_cache_replace(struct dns_cache_key *cache_key, int ttl, int spee
 	dns_cache->info.is_visited = 1;
 	old_cache_data = dns_cache->cache_data;
 	dns_cache->cache_data = cache_data;
-	list_del_init(&dns_cache->list);
+	list_del(&dns_cache->list);
 
 	if (inactive == 0) {
 		time(&dns_cache->info.insert_time);
 		time(&dns_cache->info.replace_time);
-		list_add_tail(&dns_cache->list, &dns_cache_head.cache_list);
+		_dns_cache_insert_sorted(dns_cache, &dns_cache_head.cache_list);
 	} else {
 		time(&dns_cache->info.replace_time);
 		list_add_tail(&dns_cache->list, &dns_cache_head.inactive_list);
@@ -354,24 +376,6 @@ static void _dns_cache_remove_by_domain(struct dns_cache_key *cache_key)
 	pthread_mutex_unlock(&dns_cache_head.lock);
 }
 
-static void _dns_cache_insert_sorted(struct dns_cache *dns_cache, struct list_head *head)
-{
-	time_t ttl;
-	struct dns_cache *tmp = NULL;
-
-	/* ascending order */
-	ttl = dns_cache->info.insert_time + dns_cache->info.ttl;
-	list_for_each_entry_reverse(tmp, head, list)
-	{
-		if ((tmp->info.insert_time + tmp->info.ttl) <= ttl) {
-			list_add(&dns_cache->list, &tmp->list);
-			return;
-		}
-	}
-
-	list_add_tail(&dns_cache->list, head);
-}
-
 static int _dns_cache_insert(struct dns_cache_info *info, struct dns_cache_data *cache_data, struct list_head *head)
 {
 	uint32_t key = 0;
@@ -607,8 +611,6 @@ void dns_cache_update(struct dns_cache *dns_cache)
 {
 	pthread_mutex_lock(&dns_cache_head.lock);
 	if (!list_empty(&dns_cache->list)) {
-		list_del_init(&dns_cache->list);
-		list_add_tail(&dns_cache->list, &dns_cache_head.cache_list);
 		dns_cache->info.hitnum += dns_cache->info.hitnum_update_add;
 		if (dns_cache->info.hitnum > DNS_CACHE_MAX_HITNUM) {
 			dns_cache->info.hitnum = DNS_CACHE_MAX_HITNUM;
@@ -720,7 +722,7 @@ void dns_cache_invalidate(dns_cache_callback precallback, int ttl_pre, unsigned
 			}
 		}
 
-		if (ttl < 0) {
+		if (ttl <= 0) {
 			if (dns_cache_head.enable_inactive && dns_cache->info.no_inactive == 0) {
 				_dns_cache_move_inactive(dns_cache);
 			} else {
@@ -745,15 +747,40 @@ void dns_cache_invalidate(dns_cache_callback precallback, int ttl_pre, unsigned
 	}
 }
 
-static int _dns_cache_read_record(int fd, uint32_t cache_number)
+static int _dns_cache_read_to_cache(struct dns_cache_record *cache_record, struct dns_cache_data *cache_data)
 {
+	struct list_head *head = NULL;
 
+	if (cache_record->type == CACHE_RECORD_TYPE_ACTIVE) {
+		head = &dns_cache_head.cache_list;
+	} else if (cache_record->type == CACHE_RECORD_TYPE_INACTIVE) {
+		head = &dns_cache_head.inactive_list;
+	} else {
+		tlog(TLOG_ERROR, "read cache record type is invalid.");
+		goto errout;
+	}
+
+	if (_dns_cache_insert(&cache_record->info, cache_data, head) != 0) {
+		tlog(TLOG_ERROR, "insert cache data failed.");
+		cache_data = NULL;
+		goto errout;
+	}
+
+	daemon_keepalive();
+
+	/* keep cache_data */
+	return -2;
+errout:
+	return -1;
+}
+
+static int _dns_cache_read_record(int fd, uint32_t cache_number, dns_cache_read_callback callback)
+{
 	unsigned int i = 0;
 	ssize_t ret = 0;
 	struct dns_cache_record cache_record;
 	struct dns_cache_data_head data_head;
 	struct dns_cache_data *cache_data = NULL;
-	struct list_head *head = NULL;
 
 	for (i = 0; i < cache_number; i++) {
 		ret = read(fd, &cache_record, sizeof(cache_record));
@@ -767,15 +794,6 @@ static int _dns_cache_read_record(int fd, uint32_t cache_number)
 			goto errout;
 		}
 
-		if (cache_record.type == CACHE_RECORD_TYPE_ACTIVE) {
-			head = &dns_cache_head.cache_list;
-		} else if (cache_record.type == CACHE_RECORD_TYPE_INACTIVE) {
-			head = &dns_cache_head.inactive_list;
-		} else {
-			tlog(TLOG_ERROR, "read cache record type is invalid.");
-			goto errout;
-		}
-
 		ret = read(fd, &data_head, sizeof(data_head));
 		if (ret != sizeof(data_head)) {
 			tlog(TLOG_ERROR, "read data head failed, %s", strerror(errno));
@@ -814,13 +832,15 @@ static int _dns_cache_read_record(int fd, uint32_t cache_number)
 			goto errout;
 		}
 
-		if (_dns_cache_insert(&cache_record.info, cache_data, head) != 0) {
-			tlog(TLOG_ERROR, "insert cache data failed.");
+		ret = callback(&cache_record, cache_data);
+		if (ret == -2) {
 			cache_data = NULL;
+		} else if (ret != 0) {
 			goto errout;
+		} else {
+			free(cache_data);
+			cache_data = NULL;
 		}
-
-		cache_data = NULL;
 	}
 
 	return 0;
@@ -831,7 +851,7 @@ static int _dns_cache_read_record(int fd, uint32_t cache_number)
 	return -1;
 }
 
-int dns_cache_load(const char *file)
+static int _dns_cache_file_read(const char *file, dns_cache_read_callback callback)
 {
 	int fd = -1;
 	ssize_t ret = 0;
@@ -864,7 +884,7 @@ int dns_cache_load(const char *file)
 	}
 
 	tlog(TLOG_INFO, "load cache file %s, total %d records", file, cache_file.cache_number);
-	if (_dns_cache_read_record(fd, cache_file.cache_number) != 0) {
+	if (_dns_cache_read_record(fd, cache_file.cache_number, callback) != 0) {
 		goto errout;
 	}
 
@@ -878,6 +898,11 @@ int dns_cache_load(const char *file)
 	return -1;
 }
 
+int dns_cache_load(const char *file)
+{
+	return _dns_cache_file_read(file, _dns_cache_read_to_cache);
+}
+
 static int _dns_cache_write_record(int fd, uint32_t *cache_number, enum CACHE_RECORD_TYPE type, struct list_head *head)
 {
 	struct dns_cache *dns_cache = NULL;
@@ -987,6 +1012,23 @@ int dns_cache_save(const char *file, int check_lock)
 	return -1;
 }
 
+static int _dns_cache_print(struct dns_cache_record *cache_record, struct dns_cache_data *cache_data)
+{
+	printf("domain: %s, qtype: %d, ttl: %d, speed: %.1fms\n", cache_record->info.domain, cache_record->info.qtype,
+		   cache_record->info.ttl, (float)cache_record->info.speed / 10);
+	return 0;
+}
+
+int dns_cache_print(const char *file)
+{
+	if (access(file, F_OK) != 0) {
+		tlog(TLOG_ERROR, "cache file %s not exist.", file);
+		return -1;
+	}
+
+	return _dns_cache_file_read(file, _dns_cache_print);
+}
+
 void dns_cache_destroy(void)
 {
 	struct dns_cache *dns_cache = NULL;
diff --git a/src/dns_cache.h b/src/dns_cache.h
index eea63c558b..1eb67ab673 100644
--- a/src/dns_cache.h
+++ b/src/dns_cache.h
@@ -188,6 +188,8 @@ int dns_cache_load(const char *file);
 
 int dns_cache_save(const char *file, int check_lock);
 
+int dns_cache_print(const char *file);
+
 const char *dns_cache_file_version(void);
 
 #ifdef __cplusplus
diff --git a/src/smartdns.c b/src/smartdns.c
index 96733bff08..c209a5dd32 100644
--- a/src/smartdns.c
+++ b/src/smartdns.c
@@ -20,6 +20,7 @@
 #include "smartdns.h"
 #include "art.h"
 #include "atomic.h"
+#include "dns_cache.h"
 #include "dns_client.h"
 #include "dns_conf.h"
 #include "dns_server.h"
@@ -31,6 +32,7 @@
 #include "util.h"
 #include <errno.h>
 #include <fcntl.h>
+#include <getopt.h>
 #include <libgen.h>
 #include <linux/capability.h>
 #include <openssl/err.h>
@@ -756,14 +758,15 @@ int main(int argc, char *argv[])
 #endif
 {
 	int ret = 0;
-	int is_foreground = 0;
+	int is_run_as_daemon = 1;
 	int opt = 0;
 	char config_file[MAX_LINE_LEN];
 	char pid_file[MAX_LINE_LEN];
 	int signal_ignore = 0;
 	sigset_t empty_sigblock;
 	struct stat sb;
-	int daemon_ret = 0;
+
+	static struct option long_options[] = {{"cache-print", required_argument, 0, 256}};
 
 	safe_strncpy(config_file, SMARTDNS_CONF_FILE, MAX_LINE_LEN);
 
@@ -778,10 +781,10 @@ int main(int argc, char *argv[])
 	sigprocmask(SIG_SETMASK, &empty_sigblock, NULL);
 	smartdns_close_allfds();
 
-	while ((opt = getopt(argc, argv, "fhc:p:SvxN:")) != -1) {
+	while ((opt = getopt_long(argc, argv, "fhc:p:SvxN:", long_options, 0)) != -1) {
 		switch (opt) {
 		case 'f':
-			is_foreground = 1;
+			is_run_as_daemon = 0;
 			break;
 		case 'c':
 			if (full_path(config_file, sizeof(config_file), optarg) != 0) {
@@ -810,6 +813,8 @@ int main(int argc, char *argv[])
 		case 'h':
 			_help();
 			return 1;
+		case 256:
+			return dns_cache_print(optarg);
 		}
 	}
 
@@ -819,20 +824,21 @@ int main(int argc, char *argv[])
 		goto errout;
 	}
 
-	if (is_foreground == 0 && dns_no_daemon == 0) {
-		daemon_ret = run_daemon();
-		if (daemon_ret < 0) {
+	if (dns_no_daemon) {
+		is_run_as_daemon = 0;
+	}
+
+	if (is_run_as_daemon) {
+		int daemon_ret = daemon_run();
+		if (daemon_ret != -2) {
 			char buff[4096];
 			char *log_path = realpath(_smartdns_log_path(), buff);
 
-			if (log_path != NULL && access(log_path, F_OK) == 0 && daemon_ret != -2) {
+			if (log_path != NULL && access(log_path, F_OK) == 0 && daemon_ret != -3 && daemon_ret != 0) {
 				fprintf(stderr, "run daemon failed, please check log at %s\n", log_path);
 			}
-			return 1;
-		}
 
-		if (daemon_ret == 0) {
-			return 0;
+			return daemon_ret;
 		}
 	}
 
@@ -841,7 +847,7 @@ int main(int argc, char *argv[])
 	}
 
 	if (strncmp(pid_file, "-", 2) != 0 && dns_no_pidfile == 0 && create_pid_file(pid_file) != 0) {
-		ret = -2;
+		ret = -3;
 		goto errout;
 	}
 
@@ -863,8 +869,8 @@ int main(int argc, char *argv[])
 		goto errout;
 	}
 
-	if (daemon_ret > 0) {
-		ret = daemon_kickoff(daemon_ret, 0, dns_conf_log_console | verbose_screen);
+	if (is_run_as_daemon) {
+		ret = daemon_kickoff(0, dns_conf_log_console | verbose_screen);
 		if (ret != 0) {
 			goto errout;
 		}
@@ -875,8 +881,8 @@ int main(int argc, char *argv[])
 	_smartdns_exit();
 	return ret;
 errout:
-	if (daemon_ret > 0) {
-		daemon_kickoff(daemon_ret, ret, dns_conf_log_console | verbose_screen);
+	if (is_run_as_daemon) {
+		daemon_kickoff(ret, dns_conf_log_console | verbose_screen);
 	}
 	smartdns_test_notify(2);
 	return 1;
diff --git a/src/util.c b/src/util.c
index ade576a9fc..793394332b 100644
--- a/src/util.c
+++ b/src/util.c
@@ -103,8 +103,20 @@ struct ipset_netlink_msg {
 	__be16 res_id;
 };
 
+enum daemon_msg_type {
+	DAEMON_MSG_KICKOFF,
+	DAEMON_MSG_KEEPALIVE,
+	DAEMON_MSG_DAEMON_PID,
+};
+
+struct daemon_msg {
+	enum daemon_msg_type type;
+	int value;
+};
+
 static int ipset_fd;
 static int pidfile_fd;
+static int daemon_fd;
 
 unsigned long get_tick_count(void)
 {
@@ -1609,14 +1621,20 @@ void close_all_fd(int keepfd)
 	return;
 }
 
-int daemon_kickoff(int fd, int status, int no_close)
+int daemon_kickoff(int status, int no_close)
 {
-	if (fd <= 0) {
+	struct daemon_msg msg;
+
+	if (daemon_fd <= 0) {
 		return -1;
 	}
 
-	int ret = write(fd, &status, sizeof(status));
-	if (ret != sizeof(status)) {
+	msg.type = DAEMON_MSG_KICKOFF;
+	msg.value = status;
+
+	int ret = write(daemon_fd, &msg, sizeof(msg));
+	if (ret != sizeof(msg)) {
+		fprintf(stderr, "notify parent process failed, %s\n", strerror(errno));
 		return -1;
 	}
 
@@ -1636,12 +1654,40 @@ int daemon_kickoff(int fd, int status, int no_close)
 		}
 	}
 
-	close(fd);
+	close(daemon_fd);
+	daemon_fd = -1;
 
 	return 0;
 }
 
-int run_daemon()
+int daemon_keepalive(void)
+{
+	struct daemon_msg msg;
+	static time_t last = 0;
+	time_t now = time(NULL);
+
+	if (daemon_fd <= 0) {
+		return -1;
+	}
+
+	if (now == last) {
+		return 0;
+	}
+
+	last = now;
+
+	msg.type = DAEMON_MSG_KEEPALIVE;
+	msg.value = 0;
+
+	int ret = write(daemon_fd, &msg, sizeof(msg));
+	if (ret != sizeof(msg)) {
+		return -1;
+	}
+
+	return 0;
+}
+
+int daemon_run(void)
 {
 	pid_t pid = 0;
 	int fds[2] = {0};
@@ -1660,7 +1706,6 @@ int run_daemon()
 	} else if (pid > 0) {
 		struct pollfd pfd;
 		int ret = 0;
-		int status = 0;
 
 		close(fds[1]);
 
@@ -1668,22 +1713,35 @@ int run_daemon()
 		pfd.events = POLLIN;
 		pfd.revents = 0;
 
-		ret = poll(&pfd, 1, 1000);
-		if (ret <= 0) {
-			fprintf(stderr, "run daemon process failed, wait child timeout\n");
-			goto errout;
-		}
+		do {
+			ret = poll(&pfd, 1, 3000);
+			if (ret <= 0) {
+				fprintf(stderr, "run daemon process failed, wait child timeout, kill child.\n");
+				goto errout;
+			}
 
-		if (!(pfd.revents & POLLIN)) {
-			goto errout;
-		}
+			if (!(pfd.revents & POLLIN)) {
+				goto errout;
+			}
 
-		ret = read(fds[0], &status, sizeof(status));
-		if (ret != sizeof(status)) {
-			goto errout;
-		}
+			struct daemon_msg msg;
+
+			ret = read(fds[0], &msg, sizeof(msg));
+			if (ret != sizeof(msg)) {
+				goto errout;
+			}
 
-		return status;
+			if (msg.type == DAEMON_MSG_KEEPALIVE) {
+				continue;
+			} else if (msg.type == DAEMON_MSG_DAEMON_PID) {
+				pid = msg.value;
+				continue;
+			} else if (msg.type == DAEMON_MSG_KICKOFF) {
+				return msg.value;
+			} else {
+				goto errout;
+			}
+		} while (true);
 	}
 
 	setsid();
@@ -1693,6 +1751,11 @@ int run_daemon()
 		fprintf(stderr, "double fork failed, %s\n", strerror(errno));
 		_exit(1);
 	} else if (pid > 0) {
+		struct daemon_msg msg;
+		int unused __attribute__((unused));
+		msg.type = DAEMON_MSG_DAEMON_PID;
+		msg.value = pid;
+		unused = write(fds[1], &msg, sizeof(msg));
 		_exit(0);
 	}
 
@@ -1701,8 +1764,9 @@ int run_daemon()
 		goto errout;
 	}
 	close(fds[0]);
-	return fds[1];
 
+	daemon_fd = fds[1];
+	return -2;
 errout:
 	kill(pid, SIGKILL);
 	return -1;
diff --git a/src/util.h b/src/util.h
index 417285d0c2..e7753433b1 100644
--- a/src/util.h
+++ b/src/util.h
@@ -147,9 +147,11 @@ void print_stack(void);
 
 void close_all_fd(int keepfd);
 
-int run_daemon(void);
+int daemon_run(void);
 
-int daemon_kickoff(int fd, int status, int no_close);
+int daemon_kickoff(int status, int no_close);
+
+int daemon_keepalive(void);
 
 int write_file(const char *filename, void *data, int data_len);