tools/perf/tests/hists_link.c - maze/linux - Git at Google

 #include "perf.h"
 #include "tests.h"
 #include "debug.h"
 #include "symbol.h"
 #include "sort.h"
 #include "evsel.h"
 #include "evlist.h"
 #include "machine.h"
 #include "thread.h"
 #include "parse-events.h"

 static struct {
 	u32 pid;
 	const char *comm;
 } fake_threads[] = {
 	{ 100, "perf" },
 	{ 200, "perf" },
 	{ 300, "bash" },
 };

 static struct {
 	u32 pid;
 	u64 start;
 	const char *filename;
 } fake_mmap_info[] = {
 	{ 100, 0x40000, "perf" },
 	{ 100, 0x50000, "libc" },
 	{ 100, 0xf0000, "[kernel]" },
 	{ 200, 0x40000, "perf" },
 	{ 200, 0x50000, "libc" },
 	{ 200, 0xf0000, "[kernel]" },
 	{ 300, 0x40000, "bash" },
 	{ 300, 0x50000, "libc" },
 	{ 300, 0xf0000, "[kernel]" },
 };

 struct fake_sym {
 	u64 start;
 	u64 length;
 	const char *name;
 };

 static struct fake_sym perf_syms[] = {
 	{ 700, 100, "main" },
 	{ 800, 100, "run_command" },
 	{ 900, 100, "cmd_record" },
 };

 static struct fake_sym bash_syms[] = {
 	{ 700, 100, "main" },
 	{ 800, 100, "xmalloc" },
 	{ 900, 100, "xfree" },
 };

 static struct fake_sym libc_syms[] = {
 	{ 700, 100, "malloc" },
 	{ 800, 100, "free" },
 	{ 900, 100, "realloc" },
 };

 static struct fake_sym kernel_syms[] = {
 	{ 700, 100, "schedule" },
 	{ 800, 100, "page_fault" },
 	{ 900, 100, "sys_perf_event_open" },
 };

 static struct {
 	const char *dso_name;
 	struct fake_sym *syms;
 	size_t nr_syms;
 } fake_symbols[] = {
 	{ "perf", perf_syms, ARRAY_SIZE(perf_syms) },
 	{ "bash", bash_syms, ARRAY_SIZE(bash_syms) },
 	{ "libc", libc_syms, ARRAY_SIZE(libc_syms) },
 	{ "[kernel]", kernel_syms, ARRAY_SIZE(kernel_syms) },
 };

 static struct machine *setup_fake_machine(struct machines *machines)
 {
 	struct machine *machine = machines__find(machines, HOST_KERNEL_ID);
 	size_t i;

 	if (machine == NULL) {
 		pr_debug("Not enough memory for machine setup\n");
 		return NULL;
 	}

 	for (i = 0; i < ARRAY_SIZE(fake_threads); i++) {
 		struct thread *thread;

 		thread = machine__findnew_thread(machine, fake_threads[i].pid,
 						 fake_threads[i].pid);
 		if (thread == NULL)
 			goto out;

 		thread__set_comm(thread, fake_threads[i].comm, 0);
 	}

 	for (i = 0; i < ARRAY_SIZE(fake_mmap_info); i++) {
 		union perf_event fake_mmap_event = {
 			.mmap = {
 				.header = { .misc = PERF_RECORD_MISC_USER, },
 				.pid = fake_mmap_info[i].pid,
 				.tid = fake_mmap_info[i].pid,
 				.start = fake_mmap_info[i].start,
 				.len = 0x1000ULL,
 				.pgoff = 0ULL,
 			},
 		};

 		strcpy(fake_mmap_event.mmap.filename,
 		       fake_mmap_info[i].filename);

 		machine__process_mmap_event(machine, &fake_mmap_event, NULL);
 	}

 	for (i = 0; i < ARRAY_SIZE(fake_symbols); i++) {
 		size_t k;
 		struct dso *dso;

 		dso = __dsos__findnew(&machine->user_dsos,
 				      fake_symbols[i].dso_name);
 		if (dso == NULL)
 			goto out;

 		/* emulate dso__load() */
 		dso__set_loaded(dso, MAP__FUNCTION);

 		for (k = 0; k < fake_symbols[i].nr_syms; k++) {
 			struct symbol *sym;
 			struct fake_sym *fsym = &fake_symbols[i].syms[k];

 			sym = symbol__new(fsym->start, fsym->length,
 					  STB_GLOBAL, fsym->name);
 			if (sym == NULL)
 				goto out;

 			symbols__insert(&dso->symbols[MAP__FUNCTION], sym);
 		}
 	}

 	return machine;

 out:
 	pr_debug("Not enough memory for machine setup\n");
 	machine__delete_threads(machine);
 	machine__delete(machine);
 	return NULL;
 }

 struct sample {
 	u32 pid;
 	u64 ip;
 	struct thread *thread;
 	struct map *map;
 	struct symbol *sym;
 };

 static struct sample fake_common_samples[] = {
 	/* perf [kernel] schedule() */
 	{ .pid = 100, .ip = 0xf0000 + 700, },
 	/* perf [perf]   main() */
 	{ .pid = 200, .ip = 0x40000 + 700, },
 	/* perf [perf]   cmd_record() */
 	{ .pid = 200, .ip = 0x40000 + 900, },
 	/* bash [bash]   xmalloc() */
 	{ .pid = 300, .ip = 0x40000 + 800, },
 	/* bash [libc]   malloc() */
 	{ .pid = 300, .ip = 0x50000 + 700, },
 };

 static struct sample fake_samples[][5] = {
 	{
 		/* perf [perf]   run_command() */
 		{ .pid = 100, .ip = 0x40000 + 800, },
 		/* perf [libc]   malloc() */
 		{ .pid = 100, .ip = 0x50000 + 700, },
 		/* perf [kernel] page_fault() */
 		{ .pid = 100, .ip = 0xf0000 + 800, },
 		/* perf [kernel] sys_perf_event_open() */
 		{ .pid = 200, .ip = 0xf0000 + 900, },
 		/* bash [libc]   free() */
 		{ .pid = 300, .ip = 0x50000 + 800, },
 	},
 	{
 		/* perf [libc]   free() */
 		{ .pid = 200, .ip = 0x50000 + 800, },
 		/* bash [libc]   malloc() */
 		{ .pid = 300, .ip = 0x50000 + 700, }, /* will be merged */
 		/* bash [bash]   xfee() */
 		{ .pid = 300, .ip = 0x40000 + 900, },
 		/* bash [libc]   realloc() */
 		{ .pid = 300, .ip = 0x50000 + 900, },
 		/* bash [kernel] page_fault() */
 		{ .pid = 300, .ip = 0xf0000 + 800, },
 	},
 };

 static int add_hist_entries(struct perf_evlist *evlist, struct machine *machine)
 {
 	struct perf_evsel *evsel;
 	struct addr_location al;
 	struct hist_entry *he;
 	struct perf_sample sample = { .cpu = 0, };
 	size_t i = 0, k;

 	/*
 	 * each evsel will have 10 samples - 5 common and 5 distinct.
 	 * However the second evsel also has a collapsed entry for
 	 * "bash [libc] malloc" so total 9 entries will be in the tree.
 	 */
 	evlist__for_each(evlist, evsel) {
 		for (k = 0; k < ARRAY_SIZE(fake_common_samples); k++) {
 			const union perf_event event = {
 				.header = {
 					.misc = PERF_RECORD_MISC_USER,
 				},
 			};

 			sample.pid = fake_common_samples[k].pid;
 			sample.ip = fake_common_samples[k].ip;
 			if (perf_event__preprocess_sample(&event, machine, &al,
 							  &sample) < 0)
 				goto out;

 			he = __hists__add_entry(&evsel->hists, &al, NULL,
 						NULL, NULL, 1, 1, 0);
 			if (he == NULL)
 				goto out;

 			fake_common_samples[k].thread = al.thread;
 			fake_common_samples[k].map = al.map;
 			fake_common_samples[k].sym = al.sym;
 		}

 		for (k = 0; k < ARRAY_SIZE(fake_samples[i]); k++) {
 			const union perf_event event = {
 				.header = {
 					.misc = PERF_RECORD_MISC_USER,
 				},
 			};

 			sample.pid = fake_samples[i][k].pid;
 			sample.ip = fake_samples[i][k].ip;
 			if (perf_event__preprocess_sample(&event, machine, &al,
 							  &sample) < 0)
 				goto out;

 			he = __hists__add_entry(&evsel->hists, &al, NULL,
 						NULL, NULL, 1, 1, 0);
 			if (he == NULL)
 				goto out;

 			fake_samples[i][k].thread = al.thread;
 			fake_samples[i][k].map = al.map;
 			fake_samples[i][k].sym = al.sym;
 		}
 		i++;
 	}

 	return 0;

 out:
 	pr_debug("Not enough memory for adding a hist entry\n");
 	return -1;
 }

 static int find_sample(struct sample *samples, size_t nr_samples,
 		       struct thread *t, struct map *m, struct symbol *s)
 {
 	while (nr_samples--) {
 		if (samples->thread == t && samples->map == m &&
 		    samples->sym == s)
 			return 1;
 		samples++;
 	}
 	return 0;
 }

 static int __validate_match(struct hists *hists)
 {
 	size_t count = 0;
 	struct rb_root *root;
 	struct rb_node *node;

 	/*
 	 * Only entries from fake_common_samples should have a pair.
 	 */
 	if (sort__need_collapse)
 		root = &hists->entries_collapsed;
 	else
 		root = hists->entries_in;

 	node = rb_first(root);
 	while (node) {
 		struct hist_entry *he;

 		he = rb_entry(node, struct hist_entry, rb_node_in);

 		if (hist_entry__has_pairs(he)) {
 			if (find_sample(fake_common_samples,
 					ARRAY_SIZE(fake_common_samples),
 					he->thread, he->ms.map, he->ms.sym)) {
 				count++;
 			} else {
 				pr_debug("Can't find the matched entry\n");
 				return -1;
 			}
 		}

 		node = rb_next(node);
 	}

 	if (count != ARRAY_SIZE(fake_common_samples)) {
 		pr_debug("Invalid count for matched entries: %zd of %zd\n",
 			 count, ARRAY_SIZE(fake_common_samples));
 		return -1;
 	}

 	return 0;
 }

 static int validate_match(struct hists *leader, struct hists *other)
 {
 	return __validate_match(leader) || __validate_match(other);
 }

 static int __validate_link(struct hists *hists, int idx)
 {
 	size_t count = 0;
 	size_t count_pair = 0;
 	size_t count_dummy = 0;
 	struct rb_root *root;
 	struct rb_node *node;

 	/*
 	 * Leader hists (idx = 0) will have dummy entries from other,
 	 * and some entries will have no pair.  However every entry
 	 * in other hists should have (dummy) pair.
 	 */
 	if (sort__need_collapse)
 		root = &hists->entries_collapsed;
 	else
 		root = hists->entries_in;

 	node = rb_first(root);
 	while (node) {
 		struct hist_entry *he;

 		he = rb_entry(node, struct hist_entry, rb_node_in);

 		if (hist_entry__has_pairs(he)) {
 			if (!find_sample(fake_common_samples,
 					 ARRAY_SIZE(fake_common_samples),
 					 he->thread, he->ms.map, he->ms.sym) &&
 			    !find_sample(fake_samples[idx],
 					 ARRAY_SIZE(fake_samples[idx]),
 					 he->thread, he->ms.map, he->ms.sym)) {
 				count_dummy++;
 			}
 			count_pair++;
 		} else if (idx) {
 			pr_debug("A entry from the other hists should have pair\n");
 			return -1;
 		}

 		count++;
 		node = rb_next(node);
 	}

 	/*
 	 * Note that we have a entry collapsed in the other (idx = 1) hists.
 	 */
 	if (idx == 0) {
 		if (count_dummy != ARRAY_SIZE(fake_samples[1]) - 1) {
 			pr_debug("Invalid count of dummy entries: %zd of %zd\n",
 				 count_dummy, ARRAY_SIZE(fake_samples[1]) - 1);
 			return -1;
 		}
 		if (count != count_pair + ARRAY_SIZE(fake_samples[0])) {
 			pr_debug("Invalid count of total leader entries: %zd of %zd\n",
 				 count, count_pair + ARRAY_SIZE(fake_samples[0]));
 			return -1;
 		}
 	} else {
 		if (count != count_pair) {
 			pr_debug("Invalid count of total other entries: %zd of %zd\n",
 				 count, count_pair);
 			return -1;
 		}
 		if (count_dummy > 0) {
 			pr_debug("Other hists should not have dummy entries: %zd\n",
 				 count_dummy);
 			return -1;
 		}
 	}

 	return 0;
 }

 static int validate_link(struct hists *leader, struct hists *other)
 {
 	return __validate_link(leader, 0) || __validate_link(other, 1);
 }

 static void print_hists(struct hists *hists)
 {
 	int i = 0;
 	struct rb_root *root;
 	struct rb_node *node;

 	if (sort__need_collapse)
 		root = &hists->entries_collapsed;
 	else
 		root = hists->entries_in;

 	pr_info("----- %s --------\n", __func__);
 	node = rb_first(root);
 	while (node) {
 		struct hist_entry *he;

 		he = rb_entry(node, struct hist_entry, rb_node_in);

 		pr_info("%2d: entry: %-8s [%-8s] %20s: period = %"PRIu64"\n",
 			i, thread__comm_str(he->thread), he->ms.map->dso->short_name,
 			he->ms.sym->name, he->stat.period);

 		i++;
 		node = rb_next(node);
 	}
 }

 int test__hists_link(void)
 {
 	int err = -1;
 	struct machines machines;
 	struct machine *machine = NULL;
 	struct perf_evsel *evsel, *first;
 	struct perf_evlist *evlist = perf_evlist__new();

 	if (evlist == NULL)
                 return -ENOMEM;

 	err = parse_events(evlist, "cpu-clock");
 	if (err)
 		goto out;
 	err = parse_events(evlist, "task-clock");
 	if (err)
 		goto out;

 	/* default sort order (comm,dso,sym) will be used */
 	if (setup_sorting() < 0)
 		goto out;

 	machines__init(&machines);

 	/* setup threads/dso/map/symbols also */
 	machine = setup_fake_machine(&machines);
 	if (!machine)
 		goto out;

 	if (verbose > 1)
 		machine__fprintf(machine, stderr);

 	/* process sample events */
 	err = add_hist_entries(evlist, machine);
 	if (err < 0)
 		goto out;

 	evlist__for_each(evlist, evsel) {
 		hists__collapse_resort(&evsel->hists, NULL);

 		if (verbose > 2)
 			print_hists(&evsel->hists);
 	}

 	first = perf_evlist__first(evlist);
 	evsel = perf_evlist__last(evlist);

 	/* match common entries */
 	hists__match(&first->hists, &evsel->hists);
 	err = validate_match(&first->hists, &evsel->hists);
 	if (err)
 		goto out;

 	/* link common and/or dummy entries */
 	hists__link(&first->hists, &evsel->hists);
 	err = validate_link(&first->hists, &evsel->hists);
 	if (err)
 		goto out;

 	err = 0;

 out:
 	/* tear down everything */
 	perf_evlist__delete(evlist);
 	machines__exit(&machines);

 	return err;
 }
	#include "perf.h"
	#include "tests.h"
	#include "debug.h"
	#include "symbol.h"
	#include "sort.h"
	#include "evsel.h"
	#include "evlist.h"
	#include "machine.h"
	#include "thread.h"
	#include "parse-events.h"

	static struct {
	u32 pid;
	const char *comm;
	} fake_threads[] = {
	{ 100, "perf" },
	{ 200, "perf" },
	{ 300, "bash" },
	};

	static struct {
	u32 pid;
	u64 start;
	const char *filename;
	} fake_mmap_info[] = {
	{ 100, 0x40000, "perf" },
	{ 100, 0x50000, "libc" },
	{ 100, 0xf0000, "[kernel]" },
	{ 200, 0x40000, "perf" },
	{ 200, 0x50000, "libc" },
	{ 200, 0xf0000, "[kernel]" },
	{ 300, 0x40000, "bash" },
	{ 300, 0x50000, "libc" },
	{ 300, 0xf0000, "[kernel]" },
	};

	struct fake_sym {
	u64 start;
	u64 length;
	const char *name;
	};

	static struct fake_sym perf_syms[] = {
	{ 700, 100, "main" },
	{ 800, 100, "run_command" },
	{ 900, 100, "cmd_record" },
	};

	static struct fake_sym bash_syms[] = {
	{ 700, 100, "main" },
	{ 800, 100, "xmalloc" },
	{ 900, 100, "xfree" },
	};

	static struct fake_sym libc_syms[] = {
	{ 700, 100, "malloc" },
	{ 800, 100, "free" },
	{ 900, 100, "realloc" },
	};

	static struct fake_sym kernel_syms[] = {
	{ 700, 100, "schedule" },
	{ 800, 100, "page_fault" },
	{ 900, 100, "sys_perf_event_open" },
	};

	static struct {
	const char *dso_name;
	struct fake_sym *syms;
	size_t nr_syms;
	} fake_symbols[] = {
	{ "perf", perf_syms, ARRAY_SIZE(perf_syms) },
	{ "bash", bash_syms, ARRAY_SIZE(bash_syms) },
	{ "libc", libc_syms, ARRAY_SIZE(libc_syms) },
	{ "[kernel]", kernel_syms, ARRAY_SIZE(kernel_syms) },
	};

	static struct machine setup_fake_machine(struct machines machines)
	{
	struct machine *machine = machines__find(machines, HOST_KERNEL_ID);
	size_t i;

	if (machine == NULL) {
	pr_debug("Not enough memory for machine setup\n");
	return NULL;
	}

	for (i = 0; i < ARRAY_SIZE(fake_threads); i++) {
	struct thread *thread;

	thread = machine__findnew_thread(machine, fake_threads[i].pid,
	fake_threads[i].pid);
	if (thread == NULL)
	goto out;

	thread__set_comm(thread, fake_threads[i].comm, 0);
	}

	for (i = 0; i < ARRAY_SIZE(fake_mmap_info); i++) {
	union perf_event fake_mmap_event = {
	.mmap = {
	.header = { .misc = PERF_RECORD_MISC_USER, },
	.pid = fake_mmap_info[i].pid,
	.tid = fake_mmap_info[i].pid,
	.start = fake_mmap_info[i].start,
	.len = 0x1000ULL,
	.pgoff = 0ULL,
	},
	};

	strcpy(fake_mmap_event.mmap.filename,
	fake_mmap_info[i].filename);

	machine__process_mmap_event(machine, &fake_mmap_event, NULL);
	}

	for (i = 0; i < ARRAY_SIZE(fake_symbols); i++) {
	size_t k;
	struct dso *dso;

	dso = __dsos__findnew(&machine->user_dsos,
	fake_symbols[i].dso_name);
	if (dso == NULL)
	goto out;

	/* emulate dso__load() */
	dso__set_loaded(dso, MAP__FUNCTION);

	for (k = 0; k < fake_symbols[i].nr_syms; k++) {
	struct symbol *sym;
	struct fake_sym *fsym = &fake_symbols[i].syms[k];

	sym = symbol__new(fsym->start, fsym->length,
	STB_GLOBAL, fsym->name);
	if (sym == NULL)
	goto out;

	symbols__insert(&dso->symbols[MAP__FUNCTION], sym);
	}
	}

	return machine;

	out:
	pr_debug("Not enough memory for machine setup\n");
	machine__delete_threads(machine);
	machine__delete(machine);
	return NULL;
	}

	struct sample {
	u32 pid;
	u64 ip;
	struct thread *thread;
	struct map *map;
	struct symbol *sym;
	};

	static struct sample fake_common_samples[] = {
	/* perf [kernel] schedule() */
	{ .pid = 100, .ip = 0xf0000 + 700, },
	/* perf [perf] main() */
	{ .pid = 200, .ip = 0x40000 + 700, },
	/* perf [perf] cmd_record() */
	{ .pid = 200, .ip = 0x40000 + 900, },
	/* bash [bash] xmalloc() */
	{ .pid = 300, .ip = 0x40000 + 800, },
	/* bash [libc] malloc() */
	{ .pid = 300, .ip = 0x50000 + 700, },
	};

	static struct sample fake_samples[][5] = {
	{
	/* perf [perf] run_command() */
	{ .pid = 100, .ip = 0x40000 + 800, },
	/* perf [libc] malloc() */
	{ .pid = 100, .ip = 0x50000 + 700, },
	/* perf [kernel] page_fault() */
	{ .pid = 100, .ip = 0xf0000 + 800, },
	/* perf [kernel] sys_perf_event_open() */
	{ .pid = 200, .ip = 0xf0000 + 900, },
	/* bash [libc] free() */
	{ .pid = 300, .ip = 0x50000 + 800, },
	},
	{
	/* perf [libc] free() */
	{ .pid = 200, .ip = 0x50000 + 800, },
	/* bash [libc] malloc() */
	{ .pid = 300, .ip = 0x50000 + 700, }, /* will be merged */
	/* bash [bash] xfee() */
	{ .pid = 300, .ip = 0x40000 + 900, },
	/* bash [libc] realloc() */
	{ .pid = 300, .ip = 0x50000 + 900, },
	/* bash [kernel] page_fault() */
	{ .pid = 300, .ip = 0xf0000 + 800, },
	},
	};

	static int add_hist_entries(struct perf_evlist evlist, struct machine machine)
	{
	struct perf_evsel *evsel;
	struct addr_location al;
	struct hist_entry *he;
	struct perf_sample sample = { .cpu = 0, };
	size_t i = 0, k;

	/*
	* each evsel will have 10 samples - 5 common and 5 distinct.
	* However the second evsel also has a collapsed entry for
	* "bash [libc] malloc" so total 9 entries will be in the tree.
	*/
	evlist__for_each(evlist, evsel) {
	for (k = 0; k < ARRAY_SIZE(fake_common_samples); k++) {
	const union perf_event event = {
	.header = {
	.misc = PERF_RECORD_MISC_USER,
	},
	};

	sample.pid = fake_common_samples[k].pid;
	sample.ip = fake_common_samples[k].ip;
	if (perf_event__preprocess_sample(&event, machine, &al,
	&sample) < 0)
	goto out;

	he = __hists__add_entry(&evsel->hists, &al, NULL,
	NULL, NULL, 1, 1, 0);
	if (he == NULL)
	goto out;

	fake_common_samples[k].thread = al.thread;
	fake_common_samples[k].map = al.map;
	fake_common_samples[k].sym = al.sym;
	}

	for (k = 0; k < ARRAY_SIZE(fake_samples[i]); k++) {
	const union perf_event event = {
	.header = {
	.misc = PERF_RECORD_MISC_USER,
	},
	};

	sample.pid = fake_samples[i][k].pid;
	sample.ip = fake_samples[i][k].ip;
	if (perf_event__preprocess_sample(&event, machine, &al,
	&sample) < 0)
	goto out;

	he = __hists__add_entry(&evsel->hists, &al, NULL,
	NULL, NULL, 1, 1, 0);
	if (he == NULL)
	goto out;

	fake_samples[i][k].thread = al.thread;
	fake_samples[i][k].map = al.map;
	fake_samples[i][k].sym = al.sym;
	}
	i++;
	}

	return 0;

	out:
	pr_debug("Not enough memory for adding a hist entry\n");
	return -1;
	}

	static int find_sample(struct sample *samples, size_t nr_samples,
	struct thread t, struct map m, struct symbol *s)
	{
	while (nr_samples--) {
	if (samples->thread == t && samples->map == m &&
	samples->sym == s)
	return 1;
	samples++;
	}
	return 0;
	}

	static int __validate_match(struct hists *hists)
	{
	size_t count = 0;
	struct rb_root *root;
	struct rb_node *node;

	/*
	* Only entries from fake_common_samples should have a pair.
	*/
	if (sort__need_collapse)
	root = &hists->entries_collapsed;
	else
	root = hists->entries_in;

	node = rb_first(root);
	while (node) {
	struct hist_entry *he;

	he = rb_entry(node, struct hist_entry, rb_node_in);

	if (hist_entry__has_pairs(he)) {
	if (find_sample(fake_common_samples,
	ARRAY_SIZE(fake_common_samples),
	he->thread, he->ms.map, he->ms.sym)) {
	count++;
	} else {
	pr_debug("Can't find the matched entry\n");
	return -1;
	}
	}

	node = rb_next(node);
	}

	if (count != ARRAY_SIZE(fake_common_samples)) {
	pr_debug("Invalid count for matched entries: %zd of %zd\n",
	count, ARRAY_SIZE(fake_common_samples));
	return -1;
	}

	return 0;
	}

	static int validate_match(struct hists leader, struct hists other)
	{
	return __validate_match(leader) \|\| __validate_match(other);
	}

	static int __validate_link(struct hists *hists, int idx)
	{
	size_t count = 0;
	size_t count_pair = 0;
	size_t count_dummy = 0;
	struct rb_root *root;
	struct rb_node *node;

	/*
	* Leader hists (idx = 0) will have dummy entries from other,
	* and some entries will have no pair. However every entry
	* in other hists should have (dummy) pair.
	*/
	if (sort__need_collapse)
	root = &hists->entries_collapsed;
	else
	root = hists->entries_in;

	node = rb_first(root);
	while (node) {
	struct hist_entry *he;

	he = rb_entry(node, struct hist_entry, rb_node_in);

	if (hist_entry__has_pairs(he)) {
	if (!find_sample(fake_common_samples,
	ARRAY_SIZE(fake_common_samples),
	he->thread, he->ms.map, he->ms.sym) &&
	!find_sample(fake_samples[idx],
	ARRAY_SIZE(fake_samples[idx]),
	he->thread, he->ms.map, he->ms.sym)) {
	count_dummy++;
	}
	count_pair++;
	} else if (idx) {
	pr_debug("A entry from the other hists should have pair\n");
	return -1;
	}

	count++;
	node = rb_next(node);
	}

	/*
	* Note that we have a entry collapsed in the other (idx = 1) hists.
	*/
	if (idx == 0) {
	if (count_dummy != ARRAY_SIZE(fake_samples[1]) - 1) {
	pr_debug("Invalid count of dummy entries: %zd of %zd\n",
	count_dummy, ARRAY_SIZE(fake_samples[1]) - 1);
	return -1;
	}
	if (count != count_pair + ARRAY_SIZE(fake_samples[0])) {
	pr_debug("Invalid count of total leader entries: %zd of %zd\n",
	count, count_pair + ARRAY_SIZE(fake_samples[0]));
	return -1;
	}
	} else {
	if (count != count_pair) {
	pr_debug("Invalid count of total other entries: %zd of %zd\n",
	count, count_pair);
	return -1;
	}
	if (count_dummy > 0) {
	pr_debug("Other hists should not have dummy entries: %zd\n",
	count_dummy);
	return -1;
	}
	}

	return 0;
	}

	static int validate_link(struct hists leader, struct hists other)
	{
	return __validate_link(leader, 0) \|\| __validate_link(other, 1);
	}

	static void print_hists(struct hists *hists)
	{
	int i = 0;
	struct rb_root *root;
	struct rb_node *node;

	if (sort__need_collapse)
	root = &hists->entries_collapsed;
	else
	root = hists->entries_in;

	pr_info("----- %s --------\n", __func__);
	node = rb_first(root);
	while (node) {
	struct hist_entry *he;

	he = rb_entry(node, struct hist_entry, rb_node_in);

	pr_info("%2d: entry: %-8s [%-8s] %20s: period = %"PRIu64"\n",
	i, thread__comm_str(he->thread), he->ms.map->dso->short_name,
	he->ms.sym->name, he->stat.period);

	i++;
	node = rb_next(node);
	}
	}

	int test__hists_link(void)
	{
	int err = -1;
	struct machines machines;
	struct machine *machine = NULL;
	struct perf_evsel evsel, first;
	struct perf_evlist *evlist = perf_evlist__new();

	if (evlist == NULL)
	return -ENOMEM;

	err = parse_events(evlist, "cpu-clock");
	if (err)
	goto out;
	err = parse_events(evlist, "task-clock");
	if (err)
	goto out;

	/* default sort order (comm,dso,sym) will be used */
	if (setup_sorting() < 0)
	goto out;

	machines__init(&machines);

	/* setup threads/dso/map/symbols also */
	machine = setup_fake_machine(&machines);
	if (!machine)
	goto out;

	if (verbose > 1)
	machine__fprintf(machine, stderr);

	/* process sample events */
	err = add_hist_entries(evlist, machine);
	if (err < 0)
	goto out;

	evlist__for_each(evlist, evsel) {
	hists__collapse_resort(&evsel->hists, NULL);

	if (verbose > 2)
	print_hists(&evsel->hists);
	}

	first = perf_evlist__first(evlist);
	evsel = perf_evlist__last(evlist);

	/* match common entries */
	hists__match(&first->hists, &evsel->hists);
	err = validate_match(&first->hists, &evsel->hists);
	if (err)
	goto out;

	/* link common and/or dummy entries */
	hists__link(&first->hists, &evsel->hists);
	err = validate_link(&first->hists, &evsel->hists);
	if (err)
	goto out;

	err = 0;

	out:
	/* tear down everything */
	perf_evlist__delete(evlist);
	machines__exit(&machines);

	return err;
	}