diff --git a/Documentation/perf_counter/Makefile b/Documentation/perf_counter/Makefile
new file mode 100644
index 0000000..b457497
--- /dev/null
+++ b/Documentation/perf_counter/Makefile
@@ -0,0 +1,12 @@
+BINS = kerneltop perfstat
+
+all: $(BINS)
+
+kerneltop: kerneltop.c perfcounters.h
+	cc -O6 -Wall -lrt `pkg-config --cflags --libs glib-2.0` -o $@ $<
+
+perfstat: kerneltop
+	ln -sf kerneltop perfstat
+
+clean:
+	rm $(BINS)
diff --git a/Documentation/perf_counter/kerneltop.c b/Documentation/perf_counter/kerneltop.c
new file mode 100644
index 0000000..cf0e30b
--- /dev/null
+++ b/Documentation/perf_counter/kerneltop.c
@@ -0,0 +1,956 @@
+/*
+ * kerneltop.c: show top kernel functions - performance counters showcase
+
+   Build with:
+
+     cc -O6 -Wall `pkg-config --cflags --libs glib-2.0` -o kerneltop kerneltop.c
+
+   Sample output:
+
+------------------------------------------------------------------------------
+ KernelTop:    2669 irqs/sec  [NMI, cache-misses/cache-refs],  (all, cpu: 2)
+------------------------------------------------------------------------------
+
+             weight         RIP          kernel function
+             ______   ________________   _______________
+
+              35.20 - ffffffff804ce74b : skb_copy_and_csum_dev
+              33.00 - ffffffff804cb740 : sock_alloc_send_skb
+              31.26 - ffffffff804ce808 : skb_push
+              22.43 - ffffffff80510004 : tcp_established_options
+              19.00 - ffffffff8027d250 : find_get_page
+              15.76 - ffffffff804e4fc9 : eth_type_trans
+              15.20 - ffffffff804d8baa : dst_release
+              14.86 - ffffffff804cf5d8 : skb_release_head_state
+              14.00 - ffffffff802217d5 : read_hpet
+              12.00 - ffffffff804ffb7f : __ip_local_out
+              11.97 - ffffffff804fc0c8 : ip_local_deliver_finish
+               8.54 - ffffffff805001a3 : ip_queue_xmit
+
+  Started by Ingo Molnar <mingo@redhat.com>
+
+  Improvements and fixes by:
+
+    Arjan van de Ven <arjan@linux.intel.com>
+    Yanmin Zhang <yanmin.zhang@intel.com>
+    Mike Galbraith <efault@gmx.de>
+
+  Released under the GPL v2. (and only v2, not any later version)
+
+ */
+#define _GNU_SOURCE
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <getopt.h>
+#include <assert.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <errno.h>
+#include <ctype.h>
+#include <time.h>
+
+#include <glib.h>
+
+#include <sys/syscall.h>
+#include <sys/ioctl.h>
+#include <sys/poll.h>
+#include <sys/prctl.h>
+#include <sys/wait.h>
+#include <sys/uio.h>
+
+#include <linux/unistd.h>
+
+#ifdef __x86_64__
+# define __NR_perf_counter_open	295
+#endif
+
+#ifdef __i386__
+# define __NR_perf_counter_open 333
+#endif
+
+/*
+ * Pick up some kernel type conventions:
+ */
+#define __user
+#define asmlinkage
+
+typedef unsigned int		__u32;
+typedef unsigned long long	__u64;
+typedef long long		__s64;
+
+/*
+ * User-space ABI bits:
+ */
+
+/*
+ * Generalized performance counter event types, used by the hw_event.type
+ * parameter of the sys_perf_counter_open() syscall:
+ */
+enum hw_event_types {
+	/*
+	 * Common hardware events, generalized by the kernel:
+	 */
+	PERF_COUNT_CPU_CYCLES		=  0,
+	PERF_COUNT_INSTRUCTIONS		=  1,
+	PERF_COUNT_CACHE_REFERENCES	=  2,
+	PERF_COUNT_CACHE_MISSES		=  3,
+	PERF_COUNT_BRANCH_INSTRUCTIONS	=  4,
+	PERF_COUNT_BRANCH_MISSES	=  5,
+	PERF_COUNT_BUS_CYCLES		=  6,
+
+	PERF_HW_EVENTS_MAX		=  7,
+
+	/*
+	 * Special "software" counters provided by the kernel, even if
+	 * the hardware does not support performance counters. These
+	 * counters measure various physical and sw events of the
+	 * kernel (and allow the profiling of them as well):
+	 */
+	PERF_COUNT_CPU_CLOCK		= -1,
+	PERF_COUNT_TASK_CLOCK		= -2,
+	PERF_COUNT_PAGE_FAULTS		= -3,
+	PERF_COUNT_CONTEXT_SWITCHES	= -4,
+	PERF_COUNT_CPU_MIGRATIONS	= -5,
+
+	PERF_SW_EVENTS_MIN		= -6,
+};
+
+/*
+ * IRQ-notification data record type:
+ */
+enum perf_counter_record_type {
+	PERF_RECORD_SIMPLE		=  0,
+	PERF_RECORD_IRQ			=  1,
+	PERF_RECORD_GROUP		=  2,
+};
+
+/*
+ * Hardware event to monitor via a performance monitoring counter:
+ */
+struct perf_counter_hw_event {
+	__s64			type;
+
+	__u64			irq_period;
+	__u64			record_type;
+	__u64			read_format;
+
+	__u64			disabled       :  1, /* off by default        */
+				nmi	       :  1, /* NMI sampling          */
+				raw	       :  1, /* raw event type        */
+				inherit	       :  1, /* children inherit it   */
+				pinned	       :  1, /* must always be on PMU */
+				exclusive      :  1, /* only group on PMU     */
+				exclude_user   :  1, /* don't count user      */
+				exclude_kernel :  1, /* ditto kernel          */
+				exclude_hv     :  1, /* ditto hypervisor      */
+				exclude_idle   :  1, /* don't count when idle */
+
+				__reserved_1   : 54;
+
+	__u32			extra_config_len;
+	__u32			__reserved_4;
+
+	__u64			__reserved_2;
+	__u64			__reserved_3;
+};
+
+/*
+ * Ioctls that can be done on a perf counter fd:
+ */
+#define PERF_COUNTER_IOC_ENABLE		_IO('$', 0)
+#define PERF_COUNTER_IOC_DISABLE	_IO('$', 1)
+
+asmlinkage int sys_perf_counter_open(
+
+	struct perf_counter_hw_event	*hw_event_uptr		__user,
+	pid_t				pid,
+	int				cpu,
+	int				group_fd,
+	unsigned long			flags)
+{
+	int ret;
+
+	ret = syscall(
+		__NR_perf_counter_open, hw_event_uptr, pid, cpu, group_fd, flags);
+#if defined(__x86_64__) || defined(__i386__)
+	if (ret < 0 && ret > -4096) {
+		errno = -ret;
+		ret = -1;
+	}
+#endif
+	return ret;
+}
+
+const char *event_types [] = {
+	"CPU cycles",
+	"instructions",
+	"cache-refs",
+	"cache-misses",
+	"branches",
+	"branch-misses",
+	"bus cycles"
+};
+
+const unsigned int default_count[] = {
+	1000000,
+	1000000,
+	  10000,
+	  10000,
+	1000000,
+	  10000,
+};
+
+/*
+ * prctl(PR_TASK_PERF_COUNTERS_DISABLE) will (cheaply) disable all
+ * counters in the current task.
+ */
+#define PR_TASK_PERF_COUNTERS_DISABLE           31
+#define PR_TASK_PERF_COUNTERS_ENABLE            32
+
+#define MAX_COUNTERS		8
+
+static int			nr_counters			= -1;
+
+static __u64			count_filter		       = 100;
+
+#define MAX_NR_CPUS		256
+
+static int			event_count[MAX_COUNTERS];
+static unsigned long		event_id[MAX_COUNTERS];
+static int			event_raw[MAX_COUNTERS];
+
+static int			tid				= -1;
+static int			profile_cpu			= -1;
+static int			nr_cpus				=  0;
+static int			nmi				=  1;
+static int			group				=  0;
+
+static char			*vmlinux;
+
+static char			*sym_filter;
+static unsigned long		filter_start;
+static unsigned long		filter_end;
+
+static int			delay_secs			=  2;
+static int			zero;
+static int			dump_symtab;
+
+struct source_line {
+	uint64_t		EIP;
+	unsigned long		count;
+	char			*line;
+};
+
+static GList			*lines;
+
+static void display_help(void)
+{
+	printf(
+	"Usage: kerneltop [<options>]\n\n"
+	"KernelTop Options (up to %d event types can be specified at once):\n\n",
+		 MAX_COUNTERS);
+	printf(
+	" -e EID    --event_id=EID     # event type ID                    [default:  0]\n"
+	"                                   0: CPU cycles\n"
+	"                                   1: instructions\n"
+	"                                   2: cache accesses\n"
+	"                                   3: cache misses\n"
+	"                                   4: branch instructions\n"
+	"                                   5: branch prediction misses\n"
+	"                                   6: bus cycles\n\n"
+	"                                rNNN: raw PMU events (eventsel+umask)\n\n"
+	" -c CNT    --count=CNT        # event period to sample\n\n"
+	" -C CPU    --cpu=CPU          # CPU (-1 for all)                 [default: -1]\n"
+	" -p PID    --pid=PID          # PID of sampled task (-1 for all) [default: -1]\n\n"
+	" -d delay  --delay=<seconds>  # sampling/display delay           [default:  2]\n"
+	" -f CNT --filter=CNT          # min-event-count filter          [default: 100]\n\n"
+	" -s symbol --symbol=<symbol>  # function to be showed annotated one-shot\n"
+	" -x path   --vmlinux=<path>   # the vmlinux binary, required for -s use:\n"
+	" -z        --zero             # zero counts after display\n"
+	" -D        --dump_symtab      # dump symbol table to stderr on startup\n"
+	"\n");
+
+	exit(0);
+}
+
+static void process_options(int argc, char *argv[])
+{
+	int error = 0, counter;
+
+	for (;;) {
+		int option_index = 0;
+		/** Options for getopt */
+		static struct option long_options[] = {
+			{"count",	required_argument,	NULL, 'c'},
+			{"cpu",		required_argument,	NULL, 'C'},
+			{"delay",	required_argument,	NULL, 'd'},
+			{"dump_symtab",	no_argument,		NULL, 'D'},
+			{"event_id",	required_argument,	NULL, 'e'},
+			{"filter",	required_argument,	NULL, 'f'},
+			{"group",	required_argument,	NULL, 'g'},
+			{"help",	no_argument,		NULL, 'h'},
+			{"nmi",		required_argument,	NULL, 'n'},
+			{"pid",		required_argument,	NULL, 'p'},
+			{"vmlinux",	required_argument,	NULL, 'x'},
+			{"symbol",	required_argument,	NULL, 's'},
+			{"zero",	no_argument,		NULL, 'z'},
+			{NULL,		0,			NULL,  0 }
+		};
+		int c = getopt_long(argc, argv, "c:C:d:De:f:g:hn:p:s:x:z",
+				    long_options, &option_index);
+		if (c == -1)
+			break;
+
+		switch (c) {
+		case 'c':
+			if (nr_counters == -1)
+				nr_counters = 0;
+			event_count[nr_counters]	=   atoi(optarg); break;
+		case 'C':
+			/* CPU and PID are mutually exclusive */
+			if (tid != -1) {
+				printf("WARNING: CPU switch overriding PID\n");
+				sleep(1);
+				tid = -1;
+			}
+			profile_cpu			=   atoi(optarg); break;
+		case 'd': delay_secs			=   atoi(optarg); break;
+		case 'D': dump_symtab			=              1; break;
+
+		case 'e':
+			nr_counters++;
+			if (nr_counters == MAX_COUNTERS) {
+				error = 1;
+				break;
+			}
+			if (*optarg == 'r') {
+				event_raw[nr_counters] = 1;
+				++optarg;
+			}
+			event_id[nr_counters] = strtol(optarg, NULL, 16);
+			break;
+
+		case 'f': count_filter			=   atoi(optarg); break;
+		case 'g': group				=   atoi(optarg); break;
+		case 'h':      				  display_help(); break;
+		case 'n': nmi				=   atoi(optarg); break;
+		case 'p':
+			/* CPU and PID are mutually exclusive */
+			if (profile_cpu != -1) {
+				printf("WARNING: PID switch overriding CPU\n");
+				sleep(1);
+				profile_cpu = -1;
+			}
+			tid				=   atoi(optarg); break;
+		case 's': sym_filter			= strdup(optarg); break;
+		case 'x': vmlinux			= strdup(optarg); break;
+		case 'z': zero				=              1; break;
+		default: error = 1; break;
+		}
+	}
+	if (error)
+		display_help();
+
+	nr_counters++;
+	if (nr_counters < 1)
+		nr_counters = 1;
+
+	for (counter = 0; counter < nr_counters; counter++) {
+		if (event_count[counter])
+			continue;
+
+		if (event_id[counter] < PERF_HW_EVENTS_MAX)
+			event_count[counter] = default_count[event_id[counter]];
+		else
+			event_count[counter] = 100000;
+	}
+}
+
+static uint64_t			min_ip;
+static uint64_t			max_ip = -1ll;
+
+struct sym_entry {
+	unsigned long long	addr;
+	char			*sym;
+	unsigned long		count[MAX_COUNTERS];
+	int			skip;
+	GList			*source;
+};
+
+#define MAX_SYMS		100000
+
+static int sym_table_count;
+
+struct sym_entry		*sym_filter_entry;
+
+static struct sym_entry		sym_table[MAX_SYMS];
+
+static void show_details(struct sym_entry *sym);
+
+/*
+ * Ordering weight: count-1 * count-1 * ... / count-n
+ */
+static double sym_weight(const struct sym_entry *sym)
+{
+	double weight;
+	int counter;
+
+	weight = sym->count[0];
+
+	for (counter = 1; counter < nr_counters-1; counter++)
+		weight *= sym->count[counter];
+
+	weight /= (sym->count[counter] + 1);
+
+	return weight;
+}
+
+static int compare(const void *__sym1, const void *__sym2)
+{
+	const struct sym_entry *sym1 = __sym1, *sym2 = __sym2;
+
+	return sym_weight(sym1) < sym_weight(sym2);
+}
+
+static time_t			last_refresh;
+static long			events;
+static long			userspace_events;
+static const char		CONSOLE_CLEAR[] = "[H[2J";
+
+static struct sym_entry		tmp[MAX_SYMS];
+
+static void print_sym_table(void)
+{
+	int i, printed;
+	int counter;
+	float events_per_sec = events/delay_secs;
+	float kevents_per_sec = (events-userspace_events)/delay_secs;
+
+	memcpy(tmp, sym_table, sizeof(sym_table[0])*sym_table_count);
+	qsort(tmp, sym_table_count, sizeof(tmp[0]), compare);
+
+	write(1, CONSOLE_CLEAR, strlen(CONSOLE_CLEAR));
+
+	printf(
+"------------------------------------------------------------------------------\n");
+	printf( " KernelTop:%8.0f irqs/sec  kernel:%3.1f%% [%s, ",
+		events_per_sec,
+		100.0 - (100.0*((events_per_sec-kevents_per_sec)/events_per_sec)),
+		nmi ? "NMI" : "IRQ");
+
+	if (nr_counters == 1)
+		printf("%d ", event_count[0]);
+
+	for (counter = 0; counter < nr_counters; counter++) {
+		if (counter)
+			printf("/");
+
+		if (event_id[counter] < PERF_HW_EVENTS_MAX)
+			printf( "%s", event_types[event_id[counter]]);
+		else
+			printf( "raw:%04lx", event_id[counter]);
+	}
+
+	printf( "], ");
+
+	if (tid != -1)
+		printf(" (tid: %d", tid);
+	else
+		printf(" (all");
+
+	if (profile_cpu != -1)
+		printf(", cpu: %d)\n", profile_cpu);
+	else {
+		if (tid != -1)
+			printf(")\n");
+		else
+			printf(", %d CPUs)\n", nr_cpus);
+	}
+
+	printf("------------------------------------------------------------------------------\n\n");
+
+	if (nr_counters == 1)
+		printf("             events");
+	else
+		printf("  weight     events");
+
+	printf("         RIP          kernel function\n"
+	       	       "  ______     ______   ________________   _______________\n\n"
+	);
+
+	printed = 0;
+	for (i = 0; i < sym_table_count; i++) {
+		int count;
+
+		if (nr_counters == 1) {
+			if (printed <= 18 &&
+					tmp[i].count[0] >= count_filter) {
+				printf("%19.2f - %016llx : %s\n",
+				  sym_weight(tmp + i), tmp[i].addr, tmp[i].sym);
+				printed++;
+			}
+		} else {
+			if (printed <= 18 &&
+					tmp[i].count[0] >= count_filter) {
+				printf("%8.1f %10ld - %016llx : %s\n",
+				  sym_weight(tmp + i),
+				  tmp[i].count[0],
+				  tmp[i].addr, tmp[i].sym);
+				printed++;
+			}
+		}
+		/*
+		 * Add decay to the counts:
+		 */
+		for (count = 0; count < nr_counters; count++)
+			sym_table[i].count[count] = zero ? 0 : sym_table[i].count[count] * 7 / 8;
+	}
+
+	if (sym_filter_entry)
+		show_details(sym_filter_entry);
+
+	last_refresh = time(NULL);
+
+	{
+		struct pollfd stdin_poll = { .fd = 0, .events = POLLIN };
+
+		if (poll(&stdin_poll, 1, 0) == 1) {
+			printf("key pressed - exiting.\n");
+			exit(0);
+		}
+	}
+}
+
+static int read_symbol(FILE *in, struct sym_entry *s)
+{
+	static int filter_match = 0;
+	char *sym, stype;
+	char str[500];
+	int rc, pos;
+
+	rc = fscanf(in, "%llx %c %499s", &s->addr, &stype, str);
+	if (rc == EOF)
+		return -1;
+
+	assert(rc == 3);
+
+	/* skip until end of line: */
+	pos = strlen(str);
+	do {
+		rc = fgetc(in);
+		if (rc == '\n' || rc == EOF || pos >= 499)
+			break;
+		str[pos] = rc;
+		pos++;
+	} while (1);
+	str[pos] = 0;
+
+	sym = str;
+
+	/* Filter out known duplicates and non-text symbols. */
+	if (!strcmp(sym, "_text"))
+		return 1;
+	if (!min_ip && !strcmp(sym, "_stext"))
+		return 1;
+	if (!strcmp(sym, "_etext") || !strcmp(sym, "_sinittext"))
+		return 1;
+	if (stype != 'T' && stype != 't')
+		return 1;
+	if (!strncmp("init_module", sym, 11) || !strncmp("cleanup_module", sym, 14))
+		return 1;
+	if (strstr(sym, "_text_start") || strstr(sym, "_text_end"))
+		return 1;
+
+	s->sym = malloc(strlen(str));
+	assert(s->sym);
+
+	strcpy((char *)s->sym, str);
+	s->skip = 0;
+
+	/* Tag events to be skipped. */
+	if (!strcmp("default_idle", s->sym) || !strcmp("cpu_idle", s->sym))
+		s->skip = 1;
+	if (!strcmp("enter_idle", s->sym) || !strcmp("exit_idle", s->sym))
+		s->skip = 1;
+
+	if (filter_match == 1) {
+		filter_end = s->addr;
+		filter_match = -1;
+		if (filter_end - filter_start > 10000) {
+			printf("hm, too large filter symbol <%s> - skipping.\n",
+				sym_filter);
+			printf("symbol filter start: %016lx\n", filter_start);
+			printf("                end: %016lx\n", filter_end);
+			filter_end = filter_start = 0;
+			sym_filter = NULL;
+			sleep(1);
+		}
+	}
+	if (filter_match == 0 && sym_filter && !strcmp(s->sym, sym_filter)) {
+		filter_match = 1;
+		filter_start = s->addr;
+	}
+
+	return 0;
+}
+
+int compare_addr(const void *__sym1, const void *__sym2)
+{
+	const struct sym_entry *sym1 = __sym1, *sym2 = __sym2;
+
+	return sym1->addr > sym2->addr;
+}
+
+static void sort_symbol_table(void)
+{
+	int i, dups;
+
+	do {
+		qsort(sym_table, sym_table_count, sizeof(sym_table[0]), compare_addr);
+		for (i = 0, dups = 0; i < sym_table_count; i++) {
+			if (sym_table[i].addr == sym_table[i+1].addr) {
+				sym_table[i+1].addr = -1ll;
+				dups++;
+			}
+		}
+		sym_table_count -= dups;
+	} while(dups);
+}
+
+static void parse_symbols(void)
+{
+	struct sym_entry *last;
+
+	FILE *kallsyms = fopen("/proc/kallsyms", "r");
+
+	if (!kallsyms) {
+		printf("Could not open /proc/kallsyms - no CONFIG_KALLSYMS_ALL=y?\n");
+		exit(-1);
+	}
+
+	while (!feof(kallsyms)) {
+		if (read_symbol(kallsyms, &sym_table[sym_table_count]) == 0) {
+			sym_table_count++;
+			assert(sym_table_count <= MAX_SYMS);
+		}
+	}
+
+	sort_symbol_table();
+	min_ip = sym_table[0].addr;
+	max_ip = sym_table[sym_table_count-1].addr;
+	last = sym_table + sym_table_count++;
+
+	last->addr = -1ll;
+	last->sym = "<end>";
+
+	if (filter_end) {
+		int count;
+		for (count=0; count < sym_table_count; count ++) {
+			if (!strcmp(sym_table[count].sym, sym_filter)) {
+				sym_filter_entry = &sym_table[count];
+				break;
+			}
+		}
+	}
+	if (dump_symtab) {
+		int i;
+
+		for (i = 0; i < sym_table_count; i++)
+			fprintf(stderr, "%llx %s\n",
+				sym_table[i].addr, sym_table[i].sym);
+	}
+}
+
+
+static void parse_vmlinux(char *filename)
+{
+	FILE *file;
+	char command[PATH_MAX*2];
+	if (!filename)
+		return;
+
+	sprintf(command, "objdump --start-address=0x%016lx --stop-address=0x%016lx -dS %s", filter_start, filter_end, filename);
+
+	file = popen(command, "r");
+	if (!file)
+		return;
+
+	while (!feof(file)) {
+		struct source_line *src;
+		size_t dummy = 0;
+		char *c;
+
+		src = malloc(sizeof(struct source_line));
+		assert(src != NULL);	
+		memset(src, 0, sizeof(struct source_line));
+
+		if (getline(&src->line, &dummy, file) < 0)
+			break;
+		if (!src->line)
+			break;
+
+		c = strchr(src->line, '\n');
+		if (c)
+			*c = 0;
+
+		lines = g_list_prepend(lines, src);
+
+		if (strlen(src->line)>8 && src->line[8] == ':')
+			src->EIP = strtoull(src->line, NULL, 16);
+		if (strlen(src->line)>8 && src->line[16] == ':')
+			src->EIP = strtoull(src->line, NULL, 16);
+	}
+	pclose(file);
+	lines = g_list_reverse(lines);
+}
+
+static void record_precise_ip(uint64_t ip)
+{
+	struct source_line *line;
+	GList *item;
+
+	item = g_list_first(lines);
+	while (item) {
+		line = item->data;
+		if (line->EIP == ip)
+			line->count++;
+		if (line->EIP > ip)
+			break;
+		item = g_list_next(item);
+	}
+}
+
+static void lookup_sym_in_vmlinux(struct sym_entry *sym)
+{
+	struct source_line *line;
+	GList *item;
+	char pattern[PATH_MAX];
+	sprintf(pattern, "<%s>:", sym->sym);
+
+	item = g_list_first(lines);
+	while (item) {
+		line = item->data;
+		if (strstr(line->line, pattern)) {
+			sym->source = item;
+			break;
+		}
+		item = g_list_next(item);
+	}
+}
+
+void show_lines(GList *item_queue, int item_queue_count)
+{
+	int i;
+	struct source_line *line;
+
+	for (i = 0; i < item_queue_count; i++) {
+		line = item_queue->data;
+		printf("%8li\t%s\n", line->count, line->line);
+		item_queue = g_list_next(item_queue);
+	}
+}
+
+#define TRACE_COUNT     3
+
+static void show_details(struct sym_entry *sym)
+{
+	struct source_line *line;
+	GList *item;
+	int displayed = 0;
+	GList *item_queue = NULL;
+	int item_queue_count = 0;
+
+	if (!sym->source)
+		lookup_sym_in_vmlinux(sym);
+	if (!sym->source)
+		return;
+
+	printf("Showing details for %s\n", sym->sym);
+
+	item = sym->source;
+	while (item) {
+		line = item->data;
+		if (displayed && strstr(line->line, ">:"))
+			break;
+
+		if (!item_queue_count)
+			item_queue = item;
+		item_queue_count ++;
+
+		if (line->count >= count_filter) {
+			show_lines(item_queue, item_queue_count);
+			item_queue_count = 0;
+			item_queue = NULL;
+		} else if (item_queue_count > TRACE_COUNT) {
+			item_queue = g_list_next(item_queue);
+			item_queue_count --;
+		}
+
+		line->count = 0;
+		displayed++;
+		if (displayed > 300)
+			break;
+		item = g_list_next(item);
+	}
+}
+
+/*
+ * Binary search in the histogram table and record the hit:
+ */
+static void record_ip(uint64_t ip, int counter)
+{
+	int left_idx, middle_idx, right_idx, idx;
+	unsigned long left, middle, right;
+
+	record_precise_ip(ip);
+
+	left_idx = 0;
+	right_idx = sym_table_count-1;
+	assert(ip <= max_ip && ip >= min_ip);
+
+	while (left_idx + 1 < right_idx) {
+		middle_idx = (left_idx + right_idx) / 2;
+
+		left   = sym_table[  left_idx].addr;
+		middle = sym_table[middle_idx].addr;
+		right  = sym_table[ right_idx].addr;
+
+		if (!(left <= middle && middle <= right)) {
+			printf("%016lx...\n%016lx...\n%016lx\n", left, middle, right);
+			printf("%d %d %d\n", left_idx, middle_idx, right_idx);
+		}
+		assert(left <= middle && middle <= right);
+		if (!(left <= ip && ip <= right)) {
+			printf(" left: %016lx\n", left);
+			printf("   ip: %016lx\n", ip);
+			printf("right: %016lx\n", right);
+		}
+		assert(left <= ip && ip <= right);
+		/*
+		 * [ left .... target .... middle .... right ]
+		 *   => right := middle
+		 */
+		if (ip < middle) {
+			right_idx = middle_idx;
+			continue;
+		}
+		/*
+		 * [ left .... middle ... target ... right ]
+		 *   => left := middle
+		 */
+		left_idx = middle_idx;
+	}
+
+	idx = left_idx;
+
+	if (!sym_table[idx].skip)
+		sym_table[idx].count[counter]++;
+	else events--;
+}
+
+static void process_event(uint64_t ip, int counter)
+{
+	events++;
+
+	if (ip < min_ip || ip > max_ip) {
+		userspace_events++;
+		return;
+	}
+
+	record_ip(ip, counter);
+}
+
+int main(int argc, char *argv[])
+{
+	struct pollfd event_array[MAX_NR_CPUS][MAX_COUNTERS];
+	struct perf_counter_hw_event hw_event;
+	int fd[MAX_NR_CPUS][MAX_COUNTERS];
+	int i, counter, group_fd;
+	unsigned int cpu;
+	uint64_t ip;
+	ssize_t res;
+	int ret;
+
+	process_options(argc, argv);
+
+	nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
+	if (tid != -1 || profile_cpu != -1)
+		nr_cpus = 1;
+
+	assert(nr_cpus <= MAX_NR_CPUS);
+
+	for (i = 0; i < nr_cpus; i++) {
+		group_fd = -1;
+		for (counter = 0; counter < nr_counters; counter++) {
+
+			cpu	= profile_cpu;
+			if (tid == -1 && profile_cpu == -1)
+				cpu = i;
+
+			memset(&hw_event, 0, sizeof(hw_event));
+			hw_event.type		= event_id[counter];
+			hw_event.raw		= event_raw[counter];
+			hw_event.irq_period	= event_count[counter];
+			hw_event.record_type	= PERF_RECORD_IRQ;
+			hw_event.nmi		= nmi;
+
+			fd[i][counter] = sys_perf_counter_open(&hw_event, tid, cpu, group_fd, 0);
+			fcntl(fd[i][counter], F_SETFL, O_NONBLOCK);
+			if (fd[i][counter] < 0) {
+				printf("kerneltop error: syscall returned with %d (%s)\n",
+					fd[i][counter], strerror(-fd[i][counter]));
+				if (fd[i][counter] == -1)
+					printf("Are you root?\n");
+				exit(-1);
+			}
+			assert(fd[i][counter] >= 0);
+
+			/*
+			 * First counter acts as the group leader:
+			 */
+			if (group && group_fd == -1)
+				group_fd = fd[i][counter];
+
+			event_array[i][counter].fd = fd[i][counter];
+			event_array[i][counter].events = POLLIN;
+		}
+	}
+
+	parse_symbols();
+	if (vmlinux && sym_filter_entry)
+		parse_vmlinux(vmlinux);
+
+	printf("KernelTop refresh period: %d seconds\n", delay_secs);
+	last_refresh = time(NULL);
+
+	while (1) {
+		int hits = events;
+
+		for (i = 0; i < nr_cpus; i++) {
+			for (counter = 0; counter < nr_counters; counter++) {
+				res = read(fd[i][counter], (char *) &ip, sizeof(ip));
+				if (res > 0) {
+					assert(res == sizeof(ip));
+
+					process_event(ip, counter);
+				}
+			}
+		}
+
+		if (time(NULL) >= last_refresh + delay_secs) {
+			print_sym_table();
+			events = userspace_events = 0;
+		}
+
+		if (hits == events)
+			ret = poll(event_array[0], nr_cpus, 1000);
+		hits = events;
+	}
+
+	return 0;
+}
diff --git a/Documentation/perf_counter/perfstat.c b/Documentation/perf_counter/perfstat.c
new file mode 100644
index 0000000..9a5808f
--- /dev/null
+++ b/Documentation/perf_counter/perfstat.c
@@ -0,0 +1,521 @@
+/*
+ * perfstat:  /usr/bin/time -alike performance counter statistics utility
+ *
+ *        It summarizes the counter events of all tasks (and child tasks),
+ *        covering all CPUs that the command (or workload) executes on.
+ *        It only counts the per-task events of the workload started,
+ *        independent of how many other tasks run on those CPUs.
+ *
+ * Build with:       cc -O2 -g -lrt -Wall -W -o perfstat perfstat.c
+ *
+ * Sample output:
+ *
+
+   $ ./perfstat -e 1 -e 3 -e 5 ls -lR /usr/include/ >/dev/null
+
+   Performance counter stats for 'ls':
+
+           163516953 instructions
+                2295 cache-misses
+             2855182 branch-misses
+
+ *
+ * Copyright (C) 2008, Red Hat Inc, Ingo Molnar <mingo@redhat.com>
+ *
+ * Released under the GPLv2 (not later).
+ *
+ * Percpu counter support by: Yanmin Zhang <yanmin_zhang@linux.intel.com>
+ * Symbolic event options by: Wu Fengguang <fengguang.wu@intel.com>
+ */
+#define _GNU_SOURCE
+
+#include <assert.h>
+#include <getopt.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <ctype.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <time.h>
+
+#include <sys/syscall.h>
+#include <sys/ioctl.h>
+#include <sys/prctl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <sys/wait.h>
+#include <sys/uio.h>
+
+#include <linux/unistd.h>
+
+#ifdef __x86_64__
+# define __NR_perf_counter_open	295
+#endif
+
+#ifdef __i386__
+# define __NR_perf_counter_open 333
+#endif
+
+#ifdef __powerpc__
+#define __NR_perf_counter_open 319
+#endif
+
+/*
+ * Pick up some kernel type conventions:
+ */
+#define __user
+#define asmlinkage
+
+typedef unsigned int		__u32;
+typedef unsigned long long	__u64;
+typedef long long		__s64;
+
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+
+/*
+ * User-space ABI bits:
+ */
+
+/*
+ * Generalized performance counter event types, used by the hw_event.type
+ * parameter of the sys_perf_counter_open() syscall:
+ */
+enum hw_event_types {
+	/*
+	 * Common hardware events, generalized by the kernel:
+	 */
+	PERF_COUNT_CPU_CYCLES		=  0,
+	PERF_COUNT_INSTRUCTIONS		=  1,
+	PERF_COUNT_CACHE_REFERENCES	=  2,
+	PERF_COUNT_CACHE_MISSES		=  3,
+	PERF_COUNT_BRANCH_INSTRUCTIONS	=  4,
+	PERF_COUNT_BRANCH_MISSES	=  5,
+	PERF_COUNT_BUS_CYCLES		=  6,
+
+	PERF_HW_EVENTS_MAX		=  7,
+
+	/*
+	 * Special "software" counters provided by the kernel, even if
+	 * the hardware does not support performance counters. These
+	 * counters measure various physical and sw events of the
+	 * kernel (and allow the profiling of them as well):
+	 */
+	PERF_COUNT_CPU_CLOCK		= -1,
+	PERF_COUNT_TASK_CLOCK		= -2,
+	PERF_COUNT_PAGE_FAULTS		= -3,
+	PERF_COUNT_CONTEXT_SWITCHES	= -4,
+	PERF_COUNT_CPU_MIGRATIONS	= -5,
+
+	PERF_SW_EVENTS_MIN		= -6,
+};
+
+/*
+ * IRQ-notification data record type:
+ */
+enum perf_counter_record_type {
+	PERF_RECORD_SIMPLE		=  0,
+	PERF_RECORD_IRQ			=  1,
+	PERF_RECORD_GROUP		=  2,
+};
+
+/*
+ * Hardware event to monitor via a performance monitoring counter:
+ */
+struct perf_counter_hw_event {
+	__s64			type;
+
+	__u64			irq_period;
+	__u64			record_type;
+	__u64			read_format;
+
+	__u64			disabled       :  1, /* off by default        */
+				nmi	       :  1, /* NMI sampling          */
+				raw	       :  1, /* raw event type        */
+				inherit	       :  1, /* children inherit it   */
+				pinned	       :  1, /* must always be on PMU */
+				exclusive      :  1, /* only group on PMU     */
+				exclude_user   :  1, /* don't count user      */
+				exclude_kernel :  1, /* ditto kernel          */
+				exclude_hv     :  1, /* ditto hypervisor      */
+				exclude_idle   :  1, /* don't count when idle */
+
+				__reserved_1   : 54;
+
+	__u32			extra_config_len;
+	__u32			__reserved_4;
+
+	__u64			__reserved_2;
+	__u64			__reserved_3;
+};
+
+/*
+ * Ioctls that can be done on a perf counter fd:
+ */
+#define PERF_COUNTER_IOC_ENABLE		_IO('$', 0)
+#define PERF_COUNTER_IOC_DISABLE	_IO('$', 1)
+
+asmlinkage int sys_perf_counter_open(
+
+	struct perf_counter_hw_event	*hw_event_uptr		__user,
+	pid_t				pid,
+	int				cpu,
+	int				group_fd,
+	unsigned long			flags)
+{
+	int ret;
+
+	ret = syscall(
+		__NR_perf_counter_open, hw_event_uptr, pid, cpu, group_fd, flags);
+#if defined(__x86_64__) || defined(__i386__)
+	if (ret < 0 && ret > -4096) {
+		errno = -ret;
+		ret = -1;
+	}
+#endif
+	return ret;
+}
+
+
+static char *hw_event_names [] = {
+	"CPU cycles",
+	"instructions",
+	"cache references",
+	"cache misses",
+	"branches",
+	"branch misses",
+	"bus cycles",
+};
+
+static char *sw_event_names [] = {
+	"cpu clock ticks",
+	"task clock ticks",
+	"pagefaults",
+	"context switches",
+	"CPU migrations",
+};
+
+struct event_symbol {
+	int event;
+	char *symbol;
+};
+
+static struct event_symbol event_symbols [] = {
+	{PERF_COUNT_CPU_CYCLES,			"cpu-cycles",		},
+	{PERF_COUNT_CPU_CYCLES,			"cycles",		},
+	{PERF_COUNT_INSTRUCTIONS,		"instructions",		},
+	{PERF_COUNT_CACHE_REFERENCES,		"cache-references",	},
+	{PERF_COUNT_CACHE_MISSES,		"cache-misses",		},
+	{PERF_COUNT_BRANCH_INSTRUCTIONS,	"branch-instructions",	},
+	{PERF_COUNT_BRANCH_INSTRUCTIONS,	"branches",		},
+	{PERF_COUNT_BRANCH_MISSES,		"branch-misses",	},
+	{PERF_COUNT_BUS_CYCLES,			"bus-cycles",		},
+	{PERF_COUNT_CPU_CLOCK,			"cpu-ticks",		},
+	{PERF_COUNT_CPU_CLOCK,			"ticks",		},
+	{PERF_COUNT_TASK_CLOCK,			"task-ticks",		},
+	{PERF_COUNT_PAGE_FAULTS,		"page-faults",		},
+	{PERF_COUNT_PAGE_FAULTS,		"faults",		},
+	{PERF_COUNT_CONTEXT_SWITCHES,		"context-switches",	},
+	{PERF_COUNT_CONTEXT_SWITCHES,		"cs",			},
+	{PERF_COUNT_CPU_MIGRATIONS,		"cpu-migrations",	},
+	{PERF_COUNT_CPU_MIGRATIONS,		"migrations",		},
+};
+
+#define MAX_COUNTERS					64
+#define MAX_NR_CPUS					256
+
+static int			nr_counters		= 0;
+static int			nr_cpus			= 0;
+
+static int			event_id[MAX_COUNTERS]	=
+					 { -2, -5, -4, -3, 0, 1, 2, 3};
+
+static int			event_raw[MAX_COUNTERS];
+
+static int			system_wide		= 0;
+
+static void display_help(void)
+{
+	unsigned int i;
+	int e;
+
+	printf(
+	"Usage: perfstat [<events...>] <cmd...>\n\n"
+	"PerfStat Options (up to %d event types can be specified):\n\n",
+		 MAX_COUNTERS);
+	printf(
+	" -e EVENT     --event=EVENT        #  symbolic-name        abbreviations");
+
+	for (i = 0, e = PERF_HW_EVENTS_MAX; i < ARRAY_SIZE(event_symbols); i++) {
+		if (e != event_symbols[i].event) {
+			e = event_symbols[i].event;
+			printf(
+	"\n                                  %2d: %-20s", e, event_symbols[i].symbol);
+		} else
+			printf(" %s", event_symbols[i].symbol);
+	}
+
+	printf("\n"
+	"                                rNNN: raw event type\n\n"
+	" -s                                # system-wide collection\n\n"
+	" -c <cmd..>   --command=<cmd..>    # command+arguments to be timed.\n"
+	"\n");
+	exit(0);
+}
+
+static int type_valid(int type)
+{
+	if (type >= PERF_HW_EVENTS_MAX)
+		return 0;
+	if (type <= PERF_SW_EVENTS_MIN)
+		return 0;
+
+	return 1;
+}
+
+static char *event_name(int ctr)
+{
+	int type = event_id[ctr];
+	static char buf[32];
+
+	if (event_raw[ctr]) {
+		sprintf(buf, "raw 0x%x", type);
+		return buf;
+	}
+	if (!type_valid(type))
+		return "unknown";
+
+	if (type >= 0)
+		return hw_event_names[type];
+
+	return sw_event_names[-type-1];
+}
+
+/*
+ * Each event can have multiple symbolic names.
+ * Symbolic names are (almost) exactly matched.
+ */
+static int match_event_symbols(char *str)
+{
+	unsigned int i;
+
+	if (isdigit(str[0]) || str[0] == '-')
+		return atoi(str);
+
+	for (i = 0; i < ARRAY_SIZE(event_symbols); i++) {
+		if (!strncmp(str, event_symbols[i].symbol,
+			     strlen(event_symbols[i].symbol)))
+			return event_symbols[i].event;
+	}
+
+	return PERF_HW_EVENTS_MAX;
+}
+
+static void parse_events(char *str)
+{
+	int type, raw;
+
+again:
+	nr_counters++;
+	if (nr_counters == MAX_COUNTERS)
+		display_help();
+
+	raw = 0;
+	if (*str == 'r') {
+		raw = 1;
+		++str;
+		type = strtol(str, NULL, 16);
+	} else {
+		type = match_event_symbols(str);
+		if (!type_valid(type))
+			display_help();
+	}
+
+	event_id[nr_counters] = type;
+	event_raw[nr_counters] = raw;
+
+	str = strstr(str, ",");
+	if (str) {
+		str++;
+		goto again;
+	}
+}
+
+static void process_options(int argc, char *argv[])
+{
+	for (;;) {
+		int option_index = 0;
+		/** Options for getopt */
+		static struct option long_options[] = {
+			{"event",	required_argument,	NULL, 'e'},
+			{"help",	no_argument,		NULL, 'h'},
+			{"command",	no_argument,		NULL, 'c'},
+			{NULL,		0,			NULL,  0 }
+		};
+		int c = getopt_long(argc, argv, "+:e:c:s",
+				    long_options, &option_index);
+		if (c == -1)
+			break;
+
+		switch (c) {
+		case 'c':
+			break;
+		case 's':
+			system_wide = 1;
+			break;
+		case 'e':
+			parse_events(optarg);
+			break;
+		default:
+			break;
+		}
+	}
+	if (optind == argc)
+		goto err;
+
+	if (!nr_counters)
+		nr_counters = 8;
+	else
+		nr_counters++;
+	return;
+
+err:
+	display_help();
+}
+
+char fault_here[1000000];
+
+#define PR_TASK_PERF_COUNTERS_DISABLE           31
+#define PR_TASK_PERF_COUNTERS_ENABLE            32
+
+static int fd[MAX_NR_CPUS][MAX_COUNTERS];
+
+static void create_counter(int counter)
+{
+	struct perf_counter_hw_event hw_event;
+
+	memset(&hw_event, 0, sizeof(hw_event));
+	hw_event.type		= event_id[counter];
+	hw_event.raw		= event_raw[counter];
+	hw_event.record_type	= PERF_RECORD_SIMPLE;
+	hw_event.nmi		= 0;
+
+	if (system_wide) {
+		int cpu;
+		for (cpu = 0; cpu < nr_cpus; cpu ++) {
+			fd[cpu][counter] = sys_perf_counter_open(&hw_event, -1, cpu, -1, 0);
+			if (fd[cpu][counter] < 0) {
+				printf("perfstat error: syscall returned with %d (%s)\n",
+						fd[cpu][counter], strerror(errno));
+				exit(-1);
+			}
+			
+		}
+	} else {
+		hw_event.inherit	= 1;
+		hw_event.disabled	= 1;
+
+		fd[0][counter] = sys_perf_counter_open(&hw_event, 0, -1, -1, 0);
+		if (fd[0][counter] < 0) {
+			printf("perfstat error: syscall returned with %d (%s)\n",
+					fd[0][counter], strerror(errno));
+			exit(-1);
+		}
+	}
+}
+
+
+#define rdclock()					\
+({							\
+	struct timespec ts;				\
+							\
+	clock_gettime(CLOCK_MONOTONIC, &ts);		\
+	ts.tv_sec * 1000000000ULL + ts.tv_nsec;		\
+})
+
+int main(int argc, char *argv[])
+{
+	unsigned long long t0, t1;
+	int counter;
+	ssize_t res;
+	int status;
+	int pid;
+
+	process_options(argc, argv);
+
+	if (system_wide) {
+		nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
+		assert(nr_cpus <= MAX_NR_CPUS);
+		assert(nr_cpus >= 0);
+	} else
+		nr_cpus = 1;
+
+	for (counter = 0; counter < nr_counters; counter++)
+		create_counter(counter);
+
+	argc -= optind;
+	argv += optind;
+
+	/*
+	 * Enable counters and exec the command:
+	 */
+	t0 = rdclock();
+	prctl(PR_TASK_PERF_COUNTERS_ENABLE);
+
+	if ((pid = fork()) < 0)
+		perror("failed to fork");
+	if (!pid) {
+		if (execvp(argv[0], argv)) {
+			perror(argv[0]);
+			exit(-1);
+		}
+	}
+	while (wait(&status) >= 0)
+		;
+	prctl(PR_TASK_PERF_COUNTERS_DISABLE);
+	t1 = rdclock();
+
+	fflush(stdout);
+
+	fprintf(stderr, "\n");
+	fprintf(stderr, " Performance counter stats for \'%s\':\n",
+		argv[0]);
+	fprintf(stderr, "\n");
+
+	for (counter = 0; counter < nr_counters; counter++) {
+		int cpu;
+		__u64 count, single_count;
+
+		count = 0;
+		for (cpu = 0; cpu < nr_cpus; cpu ++) {
+			res = read(fd[cpu][counter],
+					(char *) &single_count, sizeof(single_count));
+			assert(res == sizeof(single_count));
+			count += single_count;
+		}
+
+		if (!event_raw[counter] &&
+		    (event_id[counter] == PERF_COUNT_CPU_CLOCK ||
+		     event_id[counter] == PERF_COUNT_TASK_CLOCK)) {
+
+			double msecs = (double)count / 1000000;
+
+			fprintf(stderr, " %14.6f  %-20s (msecs)\n",
+				msecs, event_name(counter));
+		} else {
+			fprintf(stderr, " %14Ld  %-20s (events)\n",
+				count, event_name(counter));
+		}
+		if (!counter)
+			fprintf(stderr, "\n");
+	}
+	fprintf(stderr, "\n");
+	fprintf(stderr, " Wall-clock time elapsed: %12.6f msecs\n",
+			(double)(t1-t0)/1e6);
+	fprintf(stderr, "\n");
+
+	return 0;
+}