builtin-report.c

/*
 * builtin-report.c
 *
 * Builtin report command: Analyze the perf.data input file,
 * look up and read DSOs and symbol information and display
 * a histogram of results, along various sorting keys.
 */
#include "builtin.h"

#include "util/util.h"

#include "util/color.h"
#include <linux/list.h>
#include "util/cache.h"
#include <linux/rbtree.h>
#include "util/symbol.h"
#include "util/string.h"
#include "util/callchain.h"
#include "util/strlist.h"
#include "util/values.h"

#include "perf.h"
#include "util/debug.h"
#include "util/header.h"

#include "util/parse-options.h"
#include "util/parse-events.h"

#include "util/thread.h"
#include "util/sort.h"
#include "util/hist.h"

static char		const *input_name = "perf.data";

static char		*dso_list_str, *comm_list_str, *sym_list_str,
			*col_width_list_str;
static struct strlist	*dso_list, *comm_list, *sym_list;

static int		force;
static int		input;

static int		full_paths;
static int		show_nr_samples;

static int		show_threads;
static struct perf_read_values	show_threads_values;

static char		default_pretty_printing_style[] = "normal";
static char		*pretty_printing_style = default_pretty_printing_style;

static unsigned long	page_size;
static unsigned long	mmap_window = 32;

static int		exclude_other = 1;

static char		callchain_default_opt[] = "fractal,0.5";

static char		__cwd[PATH_MAX];
static char		*cwd = __cwd;
static int		cwdlen;

static struct rb_root	threads;
static struct thread	*last_match;

static struct perf_header *header;

static u64		sample_type;

static size_t ipchain__fprintf_graph_line(FILE *fp, int depth, int depth_mask)
{
	int i;
	size_t ret = 0;

	ret += fprintf(fp, "%s", "                ");

	for (i = 0; i < depth; i++)
		if (depth_mask & (1 << i))
			ret += fprintf(fp, "|          ");
		else
			ret += fprintf(fp, "           ");

	ret += fprintf(fp, "\n");

	return ret;
}
static size_t
ipchain__fprintf_graph(FILE *fp, struct callchain_list *chain, int depth,
		       int depth_mask, int count, u64 total_samples,
		       int hits)
{
	int i;
	size_t ret = 0;

	ret += fprintf(fp, "%s", "                ");
	for (i = 0; i < depth; i++) {
		if (depth_mask & (1 << i))
			ret += fprintf(fp, "|");
		else
			ret += fprintf(fp, " ");
		if (!count && i == depth - 1) {
			double percent;

			percent = hits * 100.0 / total_samples;
			ret += percent_color_fprintf(fp, "--%2.2f%%-- ", percent);
		} else
			ret += fprintf(fp, "%s", "          ");
	}
	if (chain->sym)
		ret += fprintf(fp, "%s\n", chain->sym->name);
	else
		ret += fprintf(fp, "%p\n", (void *)(long)chain->ip);

	return ret;
}

static struct symbol *rem_sq_bracket;
static struct callchain_list rem_hits;

static void init_rem_hits(void)
{
	rem_sq_bracket = malloc(sizeof(*rem_sq_bracket) + 6);
	if (!rem_sq_bracket) {
		fprintf(stderr, "Not enough memory to display remaining hits\n");
		return;
	}

	strcpy(rem_sq_bracket->name, "[...]");
	rem_hits.sym = rem_sq_bracket;
}

static size_t
callchain__fprintf_graph(FILE *fp, struct callchain_node *self,
			u64 total_samples, int depth, int depth_mask)
{
	struct rb_node *node, *next;
	struct callchain_node *child;
	struct callchain_list *chain;
	int new_depth_mask = depth_mask;
	u64 new_total;
	u64 remaining;
	size_t ret = 0;
	int i;

	if (callchain_param.mode == CHAIN_GRAPH_REL)
		new_total = self->children_hit;
	else
		new_total = total_samples;

	remaining = new_total;

	node = rb_first(&self->rb_root);
	while (node) {
		u64 cumul;

		child = rb_entry(node, struct callchain_node, rb_node);
		cumul = cumul_hits(child);
		remaining -= cumul;

		/*
		 * The depth mask manages the output of pipes that show
		 * the depth. We don't want to keep the pipes of the current
		 * level for the last child of this depth.
		 * Except if we have remaining filtered hits. They will
		 * supersede the last child
		 */
		next = rb_next(node);
		if (!next && (callchain_param.mode != CHAIN_GRAPH_REL || !remaining))
			new_depth_mask &= ~(1 << (depth - 1));

		/*
		 * But we keep the older depth mask for the line seperator
		 * to keep the level link until we reach the last child
		 */
		ret += ipchain__fprintf_graph_line(fp, depth, depth_mask);
		i = 0;
		list_for_each_entry(chain, &child->val, list) {
			if (chain->ip >= PERF_CONTEXT_MAX)
				continue;
			ret += ipchain__fprintf_graph(fp, chain, depth,
						      new_depth_mask, i++,
						      new_total,
						      cumul);
		}
		ret += callchain__fprintf_graph(fp, child, new_total,
						depth + 1,
						new_depth_mask | (1 << depth));
		node = next;
	}

	if (callchain_param.mode == CHAIN_GRAPH_REL &&
		remaining && remaining != new_total) {

		if (!rem_sq_bracket)
			return ret;

		new_depth_mask &= ~(1 << (depth - 1));

		ret += ipchain__fprintf_graph(fp, &rem_hits, depth,
					      new_depth_mask, 0, new_total,
					      remaining);
	}

	return ret;
}

static size_t
callchain__fprintf_flat(FILE *fp, struct callchain_node *self,
			u64 total_samples)
{
	struct callchain_list *chain;
	size_t ret = 0;

	if (!self)
		return 0;

	ret += callchain__fprintf_flat(fp, self->parent, total_samples);


	list_for_each_entry(chain, &self->val, list) {
		if (chain->ip >= PERF_CONTEXT_MAX)
			continue;
		if (chain->sym)
			ret += fprintf(fp, "                %s\n", chain->sym->name);
		else
			ret += fprintf(fp, "                %p\n",
					(void *)(long)chain->ip);
	}

	return ret;
}

static size_t
hist_entry_callchain__fprintf(FILE *fp, struct hist_entry *self,
			      u64 total_samples)
{
	struct rb_node *rb_node;
	struct callchain_node *chain;
	size_t ret = 0;

	rb_node = rb_first(&self->sorted_chain);
	while (rb_node) {
		double percent;

		chain = rb_entry(rb_node, struct callchain_node, rb_node);
		percent = chain->hit * 100.0 / total_samples;
		switch (callchain_param.mode) {
		case CHAIN_FLAT:
			ret += percent_color_fprintf(fp, "           %6.2f%%\n",
						     percent);
			ret += callchain__fprintf_flat(fp, chain, total_samples);
			break;
		case CHAIN_GRAPH_ABS: /* Falldown */
		case CHAIN_GRAPH_REL:
			ret += callchain__fprintf_graph(fp, chain,
							total_samples, 1, 1);
		case CHAIN_NONE:
		default:
			break;
		}
		ret += fprintf(fp, "\n");
		rb_node = rb_next(rb_node);
	}

	return ret;
}

static size_t
hist_entry__fprintf(FILE *fp, struct hist_entry *self, u64 total_samples)
{
	struct sort_entry *se;
	size_t ret;

	if (exclude_other && !self->parent)
		return 0;

	if (total_samples)
		ret = percent_color_fprintf(fp,
					    field_sep ? "%.2f" : "   %6.2f%%",
					(self->count * 100.0) / total_samples);
	else
		ret = fprintf(fp, field_sep ? "%lld" : "%12lld ", self->count);

	if (show_nr_samples) {
		if (field_sep)
			fprintf(fp, "%c%lld", *field_sep, self->count);
		else
			fprintf(fp, "%11lld", self->count);
	}

	list_for_each_entry(se, &hist_entry__sort_list, list) {
		if (se->elide)
			continue;

		fprintf(fp, "%s", field_sep ?: "  ");
		ret += se->print(fp, self, se->width ? *se->width : 0);
	}

	ret += fprintf(fp, "\n");

	if (callchain)
		hist_entry_callchain__fprintf(fp, self, total_samples);

	return ret;
}

/*
 *
 */

static void dso__calc_col_width(struct dso *self)
{
	if (!col_width_list_str && !field_sep &&
	    (!dso_list || strlist__has_entry(dso_list, self->name))) {
		unsigned int slen = strlen(self->name);
		if (slen > dsos__col_width)
			dsos__col_width = slen;
	}

	self->slen_calculated = 1;
}

static void thread__comm_adjust(struct thread *self)
{
	char *comm = self->comm;

	if (!col_width_list_str && !field_sep &&
	    (!comm_list || strlist__has_entry(comm_list, comm))) {
		unsigned int slen = strlen(comm);

		if (slen > comms__col_width) {
			comms__col_width = slen;
			threads__col_width = slen + 6;
		}
	}
}

static int thread__set_comm_adjust(struct thread *self, const char *comm)
{
	int ret = thread__set_comm(self, comm);

	if (ret)
		return ret;

	thread__comm_adjust(self);

	return 0;
}


static struct symbol *
resolve_symbol(struct thread *thread, struct map **mapp, u64 *ipp)
{
	struct map *map = mapp ? *mapp : NULL;
	u64 ip = *ipp;

	if (map)
		goto got_map;

	if (!thread)
		return NULL;

	map = thread__find_map(thread, ip);
	if (map != NULL) {
		/*
		 * We have to do this here as we may have a dso
		 * with no symbol hit that has a name longer than
		 * the ones with symbols sampled.
		 */
		if (!sort_dso.elide && !map->dso->slen_calculated)
			dso__calc_col_width(map->dso);

		if (mapp)
			*mapp = map;
got_map:
		ip = map->map_ip(map, ip);
	} else {
		/*
		 * If this is outside of all known maps,
		 * and is a negative address, try to look it
		 * up in the kernel dso, as it might be a
		 * vsyscall or vdso (which executes in user-mode).
		 *
		 * XXX This is nasty, we should have a symbol list in
		 * the "[vdso]" dso, but for now lets use the old
		 * trick of looking in the whole kernel symbol list.
		 */
		if ((long long)ip < 0) {
			map = kernel_map;
			if (mapp)
				*mapp = map;
		}
	}
	dump_printf(" ...... dso: %s\n",
		    map ? map->dso->long_name : "<not found>");
	dump_printf(" ...... map: %Lx -> %Lx\n", *ipp, ip);
	*ipp  = ip;

	return map ? map->dso->find_symbol(map->dso, ip) : NULL;
}

static int call__match(struct symbol *sym)
{
	if (sym->name && !regexec(&parent_regex, sym->name, 0, NULL, 0))
		return 1;

	return 0;
}

static struct symbol **resolve_callchain(struct thread *thread, struct map *map,
					 struct ip_callchain *chain,
					 struct symbol **parent)
{
	u64 context = PERF_CONTEXT_MAX;
	struct symbol **syms = NULL;
	unsigned int i;

	if (callchain) {
		syms = calloc(chain->nr, sizeof(*syms));
		if (!syms) {
			fprintf(stderr, "Can't allocate memory for symbols\n");
			exit(-1);
		}
	}

	for (i = 0; i < chain->nr; i++) {
		u64 ip = chain->ips[i];
		struct symbol *sym = NULL;

		if (ip >= PERF_CONTEXT_MAX) {
			context = ip;
			continue;
		}

		switch (context) {
		case PERF_CONTEXT_HV:
			break;
		case PERF_CONTEXT_KERNEL:
			sym = kernel_maps__find_symbol(ip, &map);
			break;
		default:
			sym = resolve_symbol(thread, &map, &ip);
			break;
		}

		if (sym) {
			if (sort__has_parent && !*parent && call__match(sym))
				*parent = sym;
			if (!callchain)
				break;
			syms[i] = sym;
		}
	}

	return syms;
}

/*
 * collect histogram counts
 */

static int
hist_entry__add(struct thread *thread, struct map *map,
		struct symbol *sym, u64 ip, struct ip_callchain *chain,
		char level, u64 count)
{
	struct symbol **syms = NULL, *parent = NULL;
	bool hit;
	struct hist_entry *he;

	if ((sort__has_parent || callchain) && chain)
		syms = resolve_callchain(thread, map, chain, &parent);

	he = __hist_entry__add(thread, map, sym, parent,
			       ip, count, level, &hit);
	if (he == NULL)
		return -ENOMEM;

	if (hit)
		he->count += count;

	if (callchain) {
		if (!hit)
			callchain_init(&he->callchain);
		append_chain(&he->callchain, chain, syms);
		free(syms);
	}

	return 0;
}

static size_t output__fprintf(FILE *fp, u64 total_samples)
{
	struct hist_entry *pos;
	struct sort_entry *se;
	struct rb_node *nd;
	size_t ret = 0;
	unsigned int width;
	char *col_width = col_width_list_str;
	int raw_printing_style;

	raw_printing_style = !strcmp(pretty_printing_style, "raw");

	init_rem_hits();

	fprintf(fp, "# Samples: %Ld\n", (u64)total_samples);
	fprintf(fp, "#\n");

	fprintf(fp, "# Overhead");
	if (show_nr_samples) {
		if (field_sep)
			fprintf(fp, "%cSamples", *field_sep);
		else
			fputs("  Samples  ", fp);
	}
	list_for_each_entry(se, &hist_entry__sort_list, list) {
		if (se->elide)
			continue;
		if (field_sep) {
			fprintf(fp, "%c%s", *field_sep, se->header);
			continue;
		}
		width = strlen(se->header);
		if (se->width) {
			if (col_width_list_str) {
				if (col_width) {
					*se->width = atoi(col_width);
					col_width = strchr(col_width, ',');
					if (col_width)
						++col_width;
				}
			}
			width = *se->width = max(*se->width, width);
		}
		fprintf(fp, "  %*s", width, se->header);
	}
	fprintf(fp, "\n");

	if (field_sep)
		goto print_entries;

	fprintf(fp, "# ........");
	if (show_nr_samples)
		fprintf(fp, " ..........");
	list_for_each_entry(se, &hist_entry__sort_list, list) {
		unsigned int i;

		if (se->elide)
			continue;

		fprintf(fp, "  ");
		if (se->width)
			width = *se->width;
		else
			width = strlen(se->header);
		for (i = 0; i < width; i++)
			fprintf(fp, ".");
	}
	fprintf(fp, "\n");

	fprintf(fp, "#\n");

print_entries:
	for (nd = rb_first(&output_hists); nd; nd = rb_next(nd)) {
		pos = rb_entry(nd, struct hist_entry, rb_node);
		ret += hist_entry__fprintf(fp, pos, total_samples);
	}

	if (sort_order == default_sort_order &&
			parent_pattern == default_parent_pattern) {
		fprintf(fp, "#\n");
		fprintf(fp, "# (For a higher level overview, try: perf report --sort comm,dso)\n");
		fprintf(fp, "#\n");
	}
	fprintf(fp, "\n");

	free(rem_sq_bracket);

	if (show_threads)
		perf_read_values_display(fp, &show_threads_values,
					 raw_printing_style);

	return ret;
}

static int validate_chain(struct ip_callchain *chain, event_t *event)
{
	unsigned int chain_size;

	chain_size = event->header.size;
	chain_size -= (unsigned long)&event->ip.__more_data - (unsigned long)event;

	if (chain->nr*sizeof(u64) > chain_size)
		return -1;

	return 0;
}

static int
process_sample_event(event_t *event, unsigned long offset, unsigned long head)
{
	char level;
	struct symbol *sym = NULL;
	struct thread *thread;
	u64 ip = event->ip.ip;
	u64 period = 1;
	struct map *map = NULL;
	void *more_data = event->ip.__more_data;
	struct ip_callchain *chain = NULL;
	int cpumode;

	thread = threads__findnew(event->ip.pid, &threads, &last_match);

	if (sample_type & PERF_SAMPLE_PERIOD) {
		period = *(u64 *)more_data;
		more_data += sizeof(u64);
	}

	dump_printf("%p [%p]: PERF_RECORD_SAMPLE (IP, %d): %d/%d: %p period: %Ld\n",
		(void *)(offset + head),
		(void *)(long)(event->header.size),
		event->header.misc,
		event->ip.pid, event->ip.tid,
		(void *)(long)ip,
		(long long)period);

	if (sample_type & PERF_SAMPLE_CALLCHAIN) {
		unsigned int i;

		chain = (void *)more_data;

		dump_printf("... chain: nr:%Lu\n", chain->nr);

		if (validate_chain(chain, event) < 0) {
			eprintf("call-chain problem with event, skipping it.\n");
			return 0;
		}

		if (dump_trace) {
			for (i = 0; i < chain->nr; i++)
				dump_printf("..... %2d: %016Lx\n", i, chain->ips[i]);
		}
	}

	dump_printf(" ... thread: %s:%d\n", thread->comm, thread->pid);

	if (thread == NULL) {
		eprintf("problem processing %d event, skipping it.\n",
			event->header.type);
		return -1;
	}

	if (comm_list && !strlist__has_entry(comm_list, thread->comm))
		return 0;

	cpumode = event->header.misc & PERF_RECORD_MISC_CPUMODE_MASK;

	if (cpumode == PERF_RECORD_MISC_KERNEL) {
		level = 'k';
		sym = kernel_maps__find_symbol(ip, &map);
		dump_printf(" ...... dso: %s\n",
			    map ? map->dso->long_name : "<not found>");
	} else if (cpumode == PERF_RECORD_MISC_USER) {
		level = '.';
		sym = resolve_symbol(thread, &map, &ip);

	} else {
		level = 'H';
		dump_printf(" ...... dso: [hypervisor]\n");
	}

	if (dso_list &&
	    (!map || !map->dso ||
	     !(strlist__has_entry(dso_list, map->dso->short_name) ||
	       (map->dso->short_name != map->dso->long_name &&
		strlist__has_entry(dso_list, map->dso->long_name)))))
		return 0;

	if (sym_list && sym && !strlist__has_entry(sym_list, sym->name))
		return 0;

	if (hist_entry__add(thread, map, sym, ip,
			    chain, level, period)) {
		eprintf("problem incrementing symbol count, skipping event\n");
		return -1;
	}

	total += period;

	return 0;
}

static int
process_mmap_event(event_t *event, unsigned long offset, unsigned long head)
{
	struct thread *thread;
	struct map *map = map__new(&event->mmap, cwd, cwdlen);

	thread = threads__findnew(event->mmap.pid, &threads, &last_match);

	dump_printf("%p [%p]: PERF_RECORD_MMAP %d/%d: [%p(%p) @ %p]: %s\n",
		(void *)(offset + head),
		(void *)(long)(event->header.size),
		event->mmap.pid,
		event->mmap.tid,
		(void *)(long)event->mmap.start,
		(void *)(long)event->mmap.len,
		(void *)(long)event->mmap.pgoff,
		event->mmap.filename);

	if (thread == NULL || map == NULL) {
		dump_printf("problem processing PERF_RECORD_MMAP, skipping event.\n");
		return 0;
	}

	thread__insert_map(thread, map);
	total_mmap++;

	return 0;
}

static int
process_comm_event(event_t *event, unsigned long offset, unsigned long head)
{
	struct thread *thread;

	thread = threads__findnew(event->comm.pid, &threads, &last_match);

	dump_printf("%p [%p]: PERF_RECORD_COMM: %s:%d\n",
		(void *)(offset + head),
		(void *)(long)(event->header.size),
		event->comm.comm, event->comm.pid);

	if (thread == NULL ||
	    thread__set_comm_adjust(thread, event->comm.comm)) {
		dump_printf("problem processing PERF_RECORD_COMM, skipping event.\n");
		return -1;
	}
	total_comm++;

	return 0;
}

static int
process_task_event(event_t *event, unsigned long offset, unsigned long head)
{
	struct thread *thread;
	struct thread *parent;

	thread = threads__findnew(event->fork.pid, &threads, &last_match);
	parent = threads__findnew(event->fork.ppid, &threads, &last_match);

	dump_printf("%p [%p]: PERF_RECORD_%s: (%d:%d):(%d:%d)\n",
		(void *)(offset + head),
		(void *)(long)(event->header.size),
		event->header.type == PERF_RECORD_FORK ? "FORK" : "EXIT",
		event->fork.pid, event->fork.tid,
		event->fork.ppid, event->fork.ptid);

	/*
	 * A thread clone will have the same PID for both
	 * parent and child.
	 */
	if (thread == parent)
		return 0;

	if (event->header.type == PERF_RECORD_EXIT)
		return 0;

	if (!thread || !parent || thread__fork(thread, parent)) {
		dump_printf("problem processing PERF_RECORD_FORK, skipping event.\n");
		return -1;
	}
	total_fork++;

	return 0;
}

static int
process_lost_event(event_t *event, unsigned long offset, unsigned long head)
{
	dump_printf("%p [%p]: PERF_RECORD_LOST: id:%Ld: lost:%Ld\n",
		(void *)(offset + head),
		(void *)(long)(event->header.size),
		event->lost.id,
		event->lost.lost);

	total_lost += event->lost.lost;

	return 0;
}

static int
process_read_event(event_t *event, unsigned long offset, unsigned long head)
{
	struct perf_event_attr *attr;

	attr = perf_header__find_attr(event->read.id, header);

	if (show_threads) {
		const char *name = attr ? __event_name(attr->type, attr->config)
				   : "unknown";
		perf_read_values_add_value(&show_threads_values,
					   event->read.pid, event->read.tid,
					   event->read.id,
					   name,
					   event->read.value);
	}

	dump_printf("%p [%p]: PERF_RECORD_READ: %d %d %s %Lu\n",
			(void *)(offset + head),
			(void *)(long)(event->header.size),
			event->read.pid,
			event->read.tid,
			attr ? __event_name(attr->type, attr->config)
			     : "FAIL",
			event->read.value);

	return 0;
}

static int
process_event(event_t *event, unsigned long offset, unsigned long head)
{
	trace_event(event);

	switch (event->header.type) {
	case PERF_RECORD_SAMPLE:
		return process_sample_event(event, offset, head);

	case PERF_RECORD_MMAP:
		return process_mmap_event(event, offset, head);

	case PERF_RECORD_COMM:
		return process_comm_event(event, offset, head);

	case PERF_RECORD_FORK:
	case PERF_RECORD_EXIT:
		return process_task_event(event, offset, head);

	case PERF_RECORD_LOST:
		return process_lost_event(event, offset, head);

	case PERF_RECORD_READ:
		return process_read_event(event, offset, head);

	/*
	 * We dont process them right now but they are fine:
	 */

	case PERF_RECORD_THROTTLE:
	case PERF_RECORD_UNTHROTTLE:
		return 0;

	default:
		return -1;
	}

	return 0;
}

static int __cmd_report(void)
{
	int ret, rc = EXIT_FAILURE;
	unsigned long offset = 0;
	unsigned long head, shift;
	struct stat input_stat;
	struct thread *idle;
	event_t *event;
	uint32_t size;
	char *buf;

	idle = register_idle_thread(&threads, &last_match);
	thread__comm_adjust(idle);

	if (show_threads)
		perf_read_values_init(&show_threads_values);

	input = open(input_name, O_RDONLY);
	if (input < 0) {
		fprintf(stderr, " failed to open file: %s", input_name);
		if (!strcmp(input_name, "perf.data"))
			fprintf(stderr, "  (try 'perf record' first)");
		fprintf(stderr, "\n");
		exit(-1);
	}

	ret = fstat(input, &input_stat);
	if (ret < 0) {
		perror("failed to stat file");
		exit(-1);
	}

	if (!force && input_stat.st_uid && (input_stat.st_uid != geteuid())) {
		fprintf(stderr, "file: %s not owned by current user or root\n", input_name);
		exit(-1);
	}

	if (!input_stat.st_size) {
		fprintf(stderr, "zero-sized file, nothing to do!\n");
		exit(0);
	}

	header = perf_header__read(input);
	head = header->data_offset;

	sample_type = perf_header__sample_type(header);

	if (!(sample_type & PERF_SAMPLE_CALLCHAIN)) {
		if (sort__has_parent) {
			fprintf(stderr, "selected --sort parent, but no"
					" callchain data. Did you call"
					" perf record without -g?\n");
			exit(-1);
		}
		if (callchain) {
			fprintf(stderr, "selected -g but no callchain data."
					" Did you call perf record without"
					" -g?\n");
			exit(-1);
		}
	} else if (callchain_param.mode != CHAIN_NONE && !callchain) {
			callchain = 1;
			if (register_callchain_param(&callchain_param) < 0) {
				fprintf(stderr, "Can't register callchain"
						" params\n");
				exit(-1);
			}
	}

	if (load_kernel() < 0) {
		perror("failed to load kernel symbols");
		return EXIT_FAILURE;
	}

	if (!full_paths) {
		if (getcwd(__cwd, sizeof(__cwd)) == NULL) {
			perror("failed to get the current directory");
			return EXIT_FAILURE;
		}
		cwdlen = strlen(cwd);
	} else {
		cwd = NULL;
		cwdlen = 0;
	}

	shift = page_size * (head / page_size);
	offset += shift;
	head -= shift;

remap:
	buf = (char *)mmap(NULL, page_size * mmap_window, PROT_READ,
			   MAP_SHARED, input, offset);
	if (buf == MAP_FAILED) {
		perror("failed to mmap file");
		exit(-1);
	}

more:
	event = (event_t *)(buf + head);

	size = event->header.size;
	if (!size)
		size = 8;

	if (head + event->header.size >= page_size * mmap_window) {
		int munmap_ret;

		shift = page_size * (head / page_size);

		munmap_ret = munmap(buf, page_size * mmap_window);
		assert(munmap_ret == 0);

		offset += shift;
		head -= shift;
		goto remap;
	}

	size = event->header.size;

	dump_printf("\n%p [%p]: event: %d\n",
			(void *)(offset + head),
			(void *)(long)event->header.size,
			event->header.type);

	if (!size || process_event(event, offset, head) < 0) {

		dump_printf("%p [%p]: skipping unknown header type: %d\n",
			(void *)(offset + head),
			(void *)(long)(event->header.size),
			event->header.type);

		total_unknown++;

		/*
		 * assume we lost track of the stream, check alignment, and
		 * increment a single u64 in the hope to catch on again 'soon'.
		 */

		if (unlikely(head & 7))
			head &= ~7ULL;