perf_counter: add sample user-space to Documentation/perf_counter/ (e0143bad) · Commits · e / devices / android_kernel_fairphone_FP4

Documentation/perf_counter/Makefile

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		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)

Documentation/perf_counter/kerneltop.c

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		/*
		* 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;
		}