diff --git a/arch/x86/tools/mcreboot-smp-x86.sh.in b/arch/x86/tools/mcreboot-smp-x86.sh.in
index 1738b19f..02d8bbc9 100644
--- a/arch/x86/tools/mcreboot-smp-x86.sh.in
+++ b/arch/x86/tools/mcreboot-smp-x86.sh.in
@@ -29,8 +29,8 @@ if [ "${BASH_VERSINFO[0]}" -lt 4 ]; then
 	exit 1
 fi
 
-INTERVAL=1
-LOGMODE=0
+redirect_kmsg=0
+mon_interval="-1"
 DUMP_LEVEL=24
 facility="LOG_LOCAL6"
 chown_option=`logname 2> /dev/null`
@@ -44,38 +44,14 @@ fi
 turbo=""
 ihk_irq=""
 
-while getopts :ti:k:c:m:o:f:r:q:d: OPT
+while getopts :tk:c:m:o:f:r:q:i:d: OPT
 do
 	case ${OPT} in
 	f)	facility=${OPTARG}
 		;;
 	o)	chown_option=${OPTARG}
 		;;
-	i)	INTERVAL=${OPTARG}
-		expr "${INTERVAL}" + 1 > /dev/null 2>&1
-		if [ $? -ge 2 ]
-		then
-			echo "invalid -i value" >&2
-			exit 1
-		fi
-		if [ ${INTERVAL} -le 0 ]
-		then
-			echo "invalid -i value" >&2
-			exit 1
-		fi
-		;;
-	k)	LOGMODE=${OPTARG}
-		expr "${LOGMODE}" + 1 > /dev/null 2>&1
-		if [ $? -ge 2 ]
-		then
-			echo "invalid -k value" >&2
-			exit 1
-		fi
-		if [ ${LOGMODE} -lt 0 -o ${LOGMODE} -gt 2 ]
-		then
-			echo "invalid -k value" >&2
-			exit 1
-		fi
+	k)	redirect_kmsg=${OPTARG}
 		;;
 	c) cpus=${OPTARG}
 		;;
@@ -89,11 +65,21 @@ do
 		;;
 	d) DUMP_LEVEL=${OPTARG}
 		;;
+	i) mon_interval=${OPTARG}
+		;;
 	*)  echo "invalid option -${OPT}" >&2
 		exit 1
 	esac
 done
 
+# Start ihkmond
+pid=`pidof ihkmond`
+if [ "${pid}" != "" ]; then
+    sudo kill -9 ${pid} > /dev/null 2> /dev/null
+fi
+if [ "${redirect_kmsg}" != "0" -o "${mon_interval}" != "-1" ]; then
+    ${SBINDIR}/ihkmond -f ${facility} -k ${redirect_kmsg} -i ${mon_interval}
+fi
 #
 # Revert any state that has been initialized before the error occured.
 #
@@ -248,7 +234,7 @@ if [ "${irqbalance_used}" == "yes" ]; then
     if ! systemctl stop irqbalance.service 2>/dev/null ; then
 		echo "error: stopping irqbalance" >&2
 		exit 1
-	fi;
+    fi;
 
     if ! etcdir=@ETCDIR@ perl -e 'use File::Copy qw(copy); $etcdir=$ENV{'etcdir'}; @files = grep { -f } glob "/proc/irq/*/smp_affinity"; foreach $file (@files) { $rel = substr($file, 1); $dir=substr($rel, 0, length($rel)-length("/smp_affinity")); if(0) { print "cp $file $etcdir/$rel\n";} if(system("mkdir -p $etcdir/$dir")){ exit 1;} if(!copy($file,"$etcdir/$rel")){ exit 1;} }'; then
 		echo "error: saving /proc/irq/*/smp_affinity" >&2
@@ -351,9 +337,15 @@ fi
 if ls /dev/mcos* 1>/dev/null 2>&1; then
 	for i in /dev/mcos*; do
 		ind=`echo $i|cut -c10-`;
-		if ! ${SBINDIR}/ihkconfig 0 destroy $ind; then
-			echo "error: destroying LWK instance $ind failed" >&2
-			error_exit "mcctrl_loaded"
+		# Retry when conflicting with ihkmond
+		nretry=0
+		until ${SBINDIR}/ihkconfig 0 destroy $ind || [ $nretry -lt 4 ]; do
+		    sleep 0.25
+		    nretry=$[ $nretry + 1 ]
+		done
+		if [ $nretry -eq 4 ]; then
+		    echo "error: destroying LWK instance $ind failed" >&2
+		    error_exit "mcctrl_loaded"
 		fi
 	done
 fi
@@ -391,7 +383,7 @@ if ! ${SBINDIR}/ihkosctl 0 load ${KERNDIR}/mckernel.img; then
 fi
 
 # Set kernel arguments
-if ! ${SBINDIR}/ihkosctl 0 kargs "hidos ksyslogd=${LOGMODE} $turbo dump_level=${DUMP_LEVEL}"; then
+if ! ${SBINDIR}/ihkosctl 0 kargs "hidos $turbo dump_level=${DUMP_LEVEL}"; then
 	echo "error: setting kernel arguments" >&2
 	error_exit "os_created"
 fi
@@ -429,14 +421,3 @@ if [ "${irqbalance_used}" == "yes" ]; then
 	fi
 #    echo cpus=$cpus ncpus=$ncpus banirq=$banirq
 fi
-
-# Start mcklogd. Note that McKernel blocks when kmsg buffer is full
-# with '-k 1' until mcklogd unblocks it so starting mcklogd must preceed
-# booting McKernel
-if [ ${LOGMODE} -ne 0 ]; then
-	# Stop mcklogd which has survived McKernel shutdown because
-	# mcstop+release.sh is not used
-	pkill mcklogd
-	SBINDIR=${SBINDIR} ${SBINDIR}/mcklogd -i ${INTERVAL} -f ${facility}
-fi
-
diff --git a/arch/x86/tools/mcstop+release-smp-x86.sh.in b/arch/x86/tools/mcstop+release-smp-x86.sh.in
index 39f37786..bc461b39 100644
--- a/arch/x86/tools/mcstop+release-smp-x86.sh.in
+++ b/arch/x86/tools/mcstop+release-smp-x86.sh.in
@@ -21,12 +21,6 @@ irqbalance_used=""
 # No SMP module? Exit.
 if ! grep ihk_smp_x86 /proc/modules &>/dev/null; then exit 0; fi
 
-# Stop mcklogd
-while pgrep "mcklogd" > /dev/null 2>&1;
-do
-	pkill -9 mcklogd
-done
-
 if [ "`systemctl status irqbalance_mck.service 2> /dev/null |grep -E 'Active: active'`" != "" ]; then
 	irqbalance_used="yes"
 	if ! systemctl stop irqbalance_mck.service 2>/dev/null; then
@@ -41,9 +35,15 @@ fi
 if ls /dev/mcos* 1>/dev/null 2>&1; then
 	for i in /dev/mcos*; do
 		ind=`echo $i|cut -c10-`;
-		if ! ${SBINDIR}/ihkconfig 0 destroy $ind; then
-			echo "error: destroying LWK instance $ind failed" >&2
-			exit 1
+		# Retry when conflicting with ihkmond
+		nretry=0
+		until ${SBINDIR}/ihkconfig 0 destroy $ind || [ $nretry -lt 4 ]; do
+		    sleep 0.25
+		    nretry=$[ $nretry + 1 ]
+		done
+		if [ $nretry -eq 4 ]; then
+		    echo "error: destroying LWK instance $ind failed" >&2
+		    exit 1
 		fi
 	done
 fi
@@ -102,6 +102,12 @@ if grep -E 'ihk\s' /proc/modules &>/dev/null; then
 	fi
 fi
 
+# Stop ihkmond
+pid=`pidof ihkmond`
+if [ "${pid}" != "" ]; then
+    sudo kill -9 ${pid} > /dev/null 2> /dev/null
+fi
+
 # Start irqbalance with the original settings
 if [ "${irqbalance_used}" != "" ]; then
 	if ! etcdir=@ETCDIR@ perl -e '$etcdir=$ENV{'etcdir'}; @files = grep { -f } glob "$etcdir/proc/irq/*/smp_affinity"; foreach $file (@files) { $dest = substr($file, length($etcdir)); if(0) {print "cp $file $dest\n";} system("cp $file $dest 2>/dev/null"); }'; then
diff --git a/executer/kernel/mcctrl/ikc.c b/executer/kernel/mcctrl/ikc.c
index 5e750112..e0d2a4ab 100644
--- a/executer/kernel/mcctrl/ikc.c
+++ b/executer/kernel/mcctrl/ikc.c
@@ -122,7 +122,7 @@ static int syscall_packet_handler(struct ihk_ikc_channel_desc *c,
 		break;
 
 	case SCD_MSG_EVENTFD:
-		dkprintf(KERN_EMERG "%s: SCD_MSG_EVENTFD,pisp->eventfd_type=%d\n", __FUNCTION__, pisp->eventfd_type);
+		dkprintf("%s: SCD_MSG_EVENTFD,pisp->eventfd_type=%d\n", __FUNCTION__, pisp->eventfd_type);
 		mcctrl_eventfd(__os, pisp);
 		break;
 
diff --git a/kernel/debug.c b/kernel/debug.c
index 7df6d2e3..1d2ab252 100644
--- a/kernel/debug.c
+++ b/kernel/debug.c
@@ -13,77 +13,22 @@
 #include <stdarg.h>
 #include <string.h>
 #include <kmsg.h>
+#include <ihk/cpu.h>
 #include <ihk/debug.h>
 #include <ihk/lock.h>
+#include <ihk/monitor.h>
+#include <errno.h>
 
-struct ihk_kmsg_buf kmsg_buf IHK_KMSG_ALIGN;
+struct ihk_kmsg_buf *kmsg_buf;
 
 extern int vsnprintf(char *buf, size_t size, const char *fmt, va_list args);
 extern int sprintf(char * buf, const char *fmt, ...);
+extern void eventfd(int type);
 static ihk_spinlock_t kmsg_lock;
+extern char *find_command_line(char *name);
 
-static unsigned long kprintf_lock_head(void);
-static void kprintf_unlock_head(unsigned long irqflags);
-
-static void kprintf_wait(int len, unsigned long *flags_head, int *slide) {
-	int head, tail, buf_len, mode, adj;
-
-	mode = kmsg_buf.mode;
-	while (1) {
-		adj = 0;
-		tail = kmsg_buf.tail;
-		buf_len = kmsg_buf.len;
-		head = kmsg_buf.head;
-		if (head < tail) head += buf_len;
-		if (tail + len > buf_len) adj = buf_len - tail;
-		if (head > tail && head <= tail + len + adj) {
-			/* When proceeding tail (producer pointer) by len would
-			   cross head (consumer pointer) in ring-buffer */
-			if (mode != 1) {
-				*slide = 1;
-				break;
-			} else {
-				kprintf_unlock_head(*flags_head);
-				*flags_head = kprintf_lock_head();
-			}
-		} else {
-			break;
-		}
-	}
-}
-
-/* TODO: lock */
-void kputs(char *buf)
-{
-	int len = strlen(buf);
-	int slide = 0;
-	unsigned long flags_tail, flags_head;
-
-	flags_tail = kprintf_lock();
-	flags_head = kprintf_lock_head();
-	kprintf_wait(len, &flags_head, &slide);
-
-	if (len + kmsg_buf.tail > kmsg_buf.len) {
-		kmsg_buf.tail = 0;
-		if(len > kmsg_buf.len) {
-			len = kmsg_buf.len;
-		}
-	}
-	
-	memcpy(kmsg_buf.str + kmsg_buf.tail, buf, len);
-	kmsg_buf.tail += len;
-	/* When proceeding tail (producer pointer) by len would
-	   cross head (consumer pointer) in ring-buffer, give up
-	   [head, tail] because the range is overwritten */
-	if (slide == 1) {
-		kmsg_buf.head = kmsg_buf.tail + 1;
-		if (kmsg_buf.head >= kmsg_buf.len) kmsg_buf.head = 0;
-	}
-	kprintf_unlock_head(flags_head);
-	kprintf_unlock(flags_tail);
-}
-
-#define KPRINTF_LOCAL_BUF_LEN 1024
+#define DEBUG_KMSG_USED (((unsigned int)kmsg_buf->tail - (unsigned int)kmsg_buf->head) % (unsigned int)kmsg_buf->len)
+#define DEBUG_KMSG_MARGIN (kmsg_buf->head == kmsg_buf->tail ? kmsg_buf->len : (((unsigned int)kmsg_buf->head - (unsigned int)kmsg_buf->tail) % (unsigned int)kmsg_buf->len))
 
 unsigned long kprintf_lock(void)
 {
@@ -95,104 +40,140 @@ void kprintf_unlock(unsigned long irqflags)
 	__ihk_mc_spinlock_unlock(&kmsg_lock, irqflags);
 }
 
-static unsigned long kprintf_lock_head(void)
-{
-	return __ihk_mc_spinlock_lock(&kmsg_buf.lock);
+#define debug_spin_lock_irqsave(lock, flags) do {						\
+		flags = cpu_disable_interrupt_save();							\
+		while (__sync_val_compare_and_swap(lock, 0, 1) != 0) {			\
+			cpu_pause();												\
+		}																\
+	} while (0)
+
+#define debug_spin_unlock_irqrestore(lock, flags) do {					\
+		*(lock) = 0;													\
+		cpu_restore_interrupt(flags);									\
+	} while (0)
+
+static void memcpy_ringbuf(char* buf, int len) {
+	int i;
+	for(i = 0; i < len; i++) {
+		*(kmsg_buf->str + kmsg_buf->tail) = *(buf + i);
+		kmsg_buf->tail = (kmsg_buf->tail + 1) % kmsg_buf->len;
+	}
 }
 
-static void kprintf_unlock_head(unsigned long irqflags)
+void kputs(char *buf)
 {
-	__ihk_mc_spinlock_unlock(&kmsg_buf.lock, irqflags);
+	int len = strlen(buf);
+	unsigned long flags_outer, flags_inner;
+	int overflow;
+
+	if (kmsg_buf == NULL) {
+		return;
+	}
+
+	flags_outer = kprintf_lock(); /* Guard from destruction */
+	debug_spin_lock_irqsave(&kmsg_buf->lock, flags_inner); /* For consistency */
+
+	overflow = DEBUG_KMSG_MARGIN <= len;
+
+	memcpy_ringbuf(buf, len);
+	
+	if (overflow) {
+		kmsg_buf->head = (kmsg_buf->tail + 1) % kmsg_buf->len;
+	}
+
+	debug_spin_unlock_irqrestore(&kmsg_buf->lock, flags_inner);
+	kprintf_unlock(flags_outer);
+
+	if (DEBUG_KMSG_USED > IHK_KMSG_HIGH_WATER_MARK) {
+		eventfd(IHK_OS_EVENTFD_TYPE_KMSG);
+		ihk_mc_delay_us(IHK_KMSG_NOTIFY_DELAY);
+	}
 }
 
+#define KPRINTF_LOCAL_BUF_LEN 1024
+
 /* Caller must hold kmsg_lock! */
 int __kprintf(const char *format, ...)
 {
 	int len = 0;
-	int slide = 0;
 	va_list va;
-	unsigned long flags_head;
 	char buf[KPRINTF_LOCAL_BUF_LEN];
+	int overflow;
+	unsigned long flags_inner;
+
+	if (kmsg_buf == NULL) {
+		return -EINVAL;
+	}
 
 	/* Copy into the local buf */
 	len = sprintf(buf, "[%3d]: ", ihk_mc_get_processor_id());
+
 	va_start(va, format);
 	len += vsnprintf(buf + len, KPRINTF_LOCAL_BUF_LEN - len - 2, format, va);
 	va_end(va);
 
-	flags_head = kprintf_lock_head();
-	kprintf_wait(len, &flags_head, &slide);
+	debug_spin_lock_irqsave(&kmsg_buf->lock, flags_inner);
 
-	/* Append to kmsg buffer */
-	if (kmsg_buf.tail + len > kmsg_buf.len) {
-		kmsg_buf.tail = 0;
+	overflow = DEBUG_KMSG_MARGIN <= len;
+
+	memcpy_ringbuf(buf, len);
+
+	if (overflow) {
+		kmsg_buf->head = (kmsg_buf->tail + 1) % kmsg_buf->len;
 	}
 
-	memcpy(kmsg_buf.str + kmsg_buf.tail, buf, len);
-	kmsg_buf.tail += len;
-	if (slide == 1) {
-		kmsg_buf.head = kmsg_buf.tail + 1;
-		if (kmsg_buf.head >= kmsg_buf.len) kmsg_buf.head = 0;
+	debug_spin_unlock_irqrestore(&kmsg_buf->lock, flags_inner);
+
+	if (DEBUG_KMSG_USED > IHK_KMSG_HIGH_WATER_MARK) {
+		eventfd(IHK_OS_EVENTFD_TYPE_KMSG);
+		ihk_mc_delay_us(IHK_KMSG_NOTIFY_DELAY);
 	}
 
-	kprintf_unlock_head(flags_head);
 	return len;
 }
 
 int kprintf(const char *format, ...)
 {
 	int len = 0;
-	int slide = 0;
 	va_list va;
-	unsigned long flags_tail, flags_head;
+	unsigned long flags_outer, flags_inner;
 	char buf[KPRINTF_LOCAL_BUF_LEN];
+	int overflow;
+
+	if (kmsg_buf == NULL) {
+		return -EINVAL;
+	}
 
 	/* Copy into the local buf */
 	len = sprintf(buf, "[%3d]: ", ihk_mc_get_processor_id());
+
 	va_start(va, format);
 	len += vsnprintf(buf + len, KPRINTF_LOCAL_BUF_LEN - len - 2, format, va);
 	va_end(va);
 
-	flags_tail = kprintf_lock();
-	flags_head = kprintf_lock_head();
-	kprintf_wait(len, &flags_head, &slide);
+	flags_outer = kprintf_lock();
+	debug_spin_lock_irqsave(&kmsg_buf->lock, flags_inner);
 
-	/* Append to kmsg buffer */
-	if (kmsg_buf.tail + len > kmsg_buf.len) {
-		kmsg_buf.tail = 0;
+	overflow = DEBUG_KMSG_MARGIN <= len;
+	
+	memcpy_ringbuf(buf, len);
+
+	if (overflow) {
+		kmsg_buf->head = (kmsg_buf->tail + 1) % kmsg_buf->len;
 	}
 
-	memcpy(kmsg_buf.str + kmsg_buf.tail, buf, len);
-	kmsg_buf.tail += len;
-	if (slide == 1) {
-		kmsg_buf.head = kmsg_buf.tail + 1;
-		if (kmsg_buf.head >= kmsg_buf.len) kmsg_buf.head = 0;
-	}
+	debug_spin_unlock_irqrestore(&kmsg_buf->lock, flags_inner);
+	kprintf_unlock(flags_outer);
 
-	kprintf_unlock_head(flags_head);
-	kprintf_unlock(flags_tail);
+	if (DEBUG_KMSG_USED > IHK_KMSG_HIGH_WATER_MARK) {
+		eventfd(IHK_OS_EVENTFD_TYPE_KMSG);
+		ihk_mc_delay_us(IHK_KMSG_NOTIFY_DELAY);
+	}
 
 	return len;
 }
 
-/* mode:
-    0: mcklogd is not running.
-       When kmsg buffer is full, writer doesn't block
-       and overwrites the buffer.
-    1: mcklogd periodically retrieves kmsg.
-       When kmsg buffer is full, writer blocks until 
-       someone retrieves kmsg.
-    2: mcklogd periodically retrieves kmsg.
-       When kmsg buffer is full, writer doesn't block
-       and overwrites the buffer.
-*/
-void kmsg_init(int mode)
+void kmsg_init()
 {
 	ihk_mc_spinlock_init(&kmsg_lock);
-	kmsg_buf.tail = 0;
-	kmsg_buf.len = sizeof(kmsg_buf.str);
-	kmsg_buf.head = 0;
-	kmsg_buf.mode = mode;
-	ihk_mc_spinlock_init(&kmsg_buf.lock);
-	memset(kmsg_buf.str, 0, kmsg_buf.len);
 }
diff --git a/kernel/include/init.h b/kernel/include/init.h
index 3e8d74e6..ed0b2c4e 100644
--- a/kernel/include/init.h
+++ b/kernel/include/init.h
@@ -14,7 +14,6 @@
 #define INIT_H
 
 extern void arch_init(void);
-extern void kmsg_init(int);
 extern void mem_init(void);
 extern void ihk_ikc_master_init(void);
 extern void ap_init(void);
diff --git a/kernel/include/kmsg.h b/kernel/include/kmsg.h
index 75e82a0e..94ffd73c 100644
--- a/kernel/include/kmsg.h
+++ b/kernel/include/kmsg.h
@@ -13,9 +13,8 @@
 #ifndef KMSG_H
 #define KMSG_H
 
+void kmsg_init(void);
 void kputs(char *buf);
 int kprintf(const char *format, ...);
 
-void kmsg_init(int);
-
 #endif
diff --git a/kernel/init.c b/kernel/init.c
index 552c6447..1382bcd5 100644
--- a/kernel/init.c
+++ b/kernel/init.c
@@ -50,7 +50,6 @@
 
 #define DUMP_LEVEL_USER_UNUSED_EXCLUDE 24
 
-extern struct ihk_kmsg_buf kmsg_buf;
 extern unsigned long ihk_mc_get_ns_per_tsc(void);
 extern long syscall(int, ihk_mc_user_context_t *);
 
@@ -424,19 +423,6 @@ extern void ibmic_cmd_init(void);
 
 int main(void)
 {
-	char *ptr;
-	int mode = 0;
-
-	ptr = find_command_line("ksyslogd=");
-	if (ptr) {
-	    mode = ptr[9] - 0x30;
-	    if (mode < 0 || mode > 2) mode = 0;
-	}
-
-	kmsg_init(mode);
-
-	kputs("IHK/McKernel started.\n");
-	ihk_set_kmsg(virt_to_phys(&kmsg_buf), IHK_KMSG_SIZE);
 	arch_init();
 
 	/*