Re: [PATCH 1/9] perf tools: add test for reading object code

[Adrian Hunter <adrian.hunter@intel.com>]

On 29/07/2013 9:28 a.m., Namhyung Kim wrote:
> Hi Adrian,
>
> Just a few nitpicks below..
>
>
> On Thu, 25 Jul 2013 17:01:22 +0300, Adrian Hunter wrote:
>> Using the information in mmap events, perf tools can read object
>> code associated with sampled addresses.  A test is added that
>> compares bytes read by perf with the same bytes read using
>> objdump.
>>
> [SNIP]
>> +
>> +static int read_objdump_line(char *line, size_t line_len, void **buf,
>> +			     size_t *len)
>> +{
>> +	size_t i;
>> +
>> +	/* Skip to a colon */
>> +	for (i = 0; i<  line_len; i++) {
>> +		if (line[i] == ':')
>> +			break;
>> +	}
>> +	if (line[i++] != ':')
>> +		return 0;
>
> strchr() ?

Fixed in V2

>
>> +
>> +	/* Read bytes */
>> +	while (*len) {
>> +		char c1, c2;
>> +
>> +		/* Skip spaces */
>> +		for (; i<  line_len; i++) {
>> +			if (!isspace(line[i]))
>> +				break;
>> +		}
>> +		/* Get 2 hex digits */
>> +		if (i>= line_len || !isxdigit(line[i]))
>> +			break;
>> +		c1 = line[i++];
>> +		if (i>= line_len || !isxdigit(line[i]))
>> +			break;
>> +		c2 = line[i++];
>> +		/* Followed by a space */
>> +		if (i<  line_len&&  line[i]&&  !isspace(line[i]))
>> +			break;
>> +		/* Store byte */
>> +		*(unsigned char *)*buf = (hex(c1)<<  4) | hex(c2);
>> +		*buf += 1;
>> +		*len -= 1;
>> +	}
>> +
>> +	return 0;
>
> It seems this function always returns 0..

Fixed in V2

>
>
>> +}
>> +
>> +static int read_objdump_output(FILE *f, void **buf, size_t *len)
>> +{
>> +	char *line = NULL;
>> +	size_t line_len;
>> +	ssize_t ret;
>> +	int err = 0;
>> +
>> +	while (1) {
>> +		ret = getline(&line,&line_len, f);
>> +		if (feof(f))
>> +			break;
>> +		if (ret<  0 || read_objdump_line(line, ret, buf, len)) {
>
> so no need to check the return value.

Fixed in V2

>
>
>> +			pr_debug("getline failed\n");
>> +			err = -1;
>> +			break;
>> +		}
>> +	}
>> +
>> +	free(line);
>> +
>> +	return err;
>> +}
>> +
> [SNIP]
>> +
>> +static int do_test_code_reading(void)
>> +{
>> +	struct machines machines;
>> +	struct machine *machine;
>> +	struct thread *thread;
>> +	struct perf_record_opts opts = {
>> +		.mmap_pages	     = UINT_MAX,
>> +		.user_freq	     = UINT_MAX,
>> +		.user_interval	     = ULLONG_MAX,
>> +		.freq		     = 40000,
>
> Is it intended to use the freq of 40000 instead of 4000 (default)?

Yes.  The "workload" is small so a higher sampling rate is preferable.

>
>
>> +		.target		     = {
>> +			.uses_mmap   = true,
>> +		},
>> +	};
>> +	struct thread_map *threads = NULL;
>> +	struct cpu_map *cpus = NULL;
>> +	struct perf_evlist *evlist = NULL;
>> +	struct perf_evsel *evsel = NULL;
>> +	int err = -1, ret;
>> +	pid_t pid;
>> +	struct map *map;
>> +	bool have_vmlinux, excl_kernel = false;
>> +
>> +	pid = getpid();
>> +
>> +	machines__init(&machines);
>> +	machine =&machines.host;
>> +
>> +	ret = machine__create_kernel_maps(machine);
>> +	if (ret<  0) {
>> +		pr_debug("machine__create_kernel_maps failed\n");
>> +		goto out_err;
>> +	}
>> +
>> +	/* Load kernel map */
>> +	map = machine->vmlinux_maps[MAP__FUNCTION];
>> +	ret = map__load(map, NULL);
>> +	if (ret<  0) {
>> +		pr_debug("map__load failed\n");
>> +		goto out_err;
>> +	}
>> +	have_vmlinux = map->dso->symtab_type == DSO_BINARY_TYPE__VMLINUX;
>> +	/* No point getting kernel events if there is no vmlinux */
>> +	if (!have_vmlinux)
>> +		excl_kernel = true;
>> +
>> +	threads = thread_map__new_by_tid(pid);
>> +	if (!threads) {
>> +		pr_debug("thread_map__new_by_tid failed\n");
>> +		goto out_err;
>> +	}
>> +
>> +	ret = perf_event__synthesize_thread_map(NULL, threads,
>> +						perf_event__process, machine);
>> +	if (ret<  0) {
>> +		pr_debug("perf_event__synthesize_thread_map failed\n");
>> +		goto out_err;
>> +	}
>> +
>> +	thread = machine__findnew_thread(machine, pid, pid);
>> +	if (!thread) {
>> +		pr_debug("machine__findnew_thread failed\n");
>> +		goto out_err;
>> +	}
>> +
>> +	cpus = cpu_map__new(NULL);
>> +	if (!cpus) {
>> +		pr_debug("cpu_map__new failed\n");
>> +		goto out_err;
>> +	}
>> +
>> +	while (1) {
>> +		const char *str;
>> +
>> +		evlist = perf_evlist__new();
>> +		if (!evlist) {
>> +			pr_debug("perf_evlist__new failed\n");
>> +			goto out_err;
>> +		}
>> +
>> +		perf_evlist__set_maps(evlist, cpus, threads);
>> +
>> +		if (excl_kernel)
>> +			str =  "cycles:u";
>
> A double whitespace.

Fixed in V2

>
>
>> +		else
>> +			str = "cycles";
>> +		pr_debug("Parsing event '%s'\n", str);
>> +		ret = parse_events(evlist, str);
>> +		if (ret<  0) {
>> +			pr_debug("parse_events failed\n");
>> +			goto out_err;
>> +		}
>> +
>> +		perf_evlist__config(evlist,&opts);
>> +
>> +		evsel = perf_evlist__first(evlist);
>> +
>> +		evsel->attr.comm = 1;
>> +		evsel->attr.disabled = 1;
>> +		evsel->attr.enable_on_exec = 0;
>> +
>> +		ret = perf_evlist__open(evlist);
>> +		if (ret<  0) {
>> +			if (!excl_kernel) {
>> +				excl_kernel = true;
>> +				continue;
>
> It seems the evlist is leaked.  perf_evlist__delete(evlist) is needed.

Fixed in V2

>
> Thanks,
> Namhyung
>
>
>> +			}
>> +			pr_debug("perf_evlist__open failed\n");
>> +			goto out_err;
>> +		}
>> +		break;
>> +	}
>> +
>> +	ret = perf_evlist__mmap(evlist, UINT_MAX, false);
>> +	if (ret<  0) {
>> +		pr_debug("perf_evlist__mmap failed\n");
>> +		goto out_err;
>> +	}
>> +
>> +	perf_evlist__enable(evlist);
>> +
>> +	do_something();
>> +
>> +	perf_evlist__disable(evlist);
>> +
>> +	ret = process_events(machine, evlist);
>> +	if (ret<  0)
>> +		goto out_err;
>> +
>> +	if (!have_vmlinux)
>> +		err = TEST_CODE_READING_NO_VMLINUX;
>> +	else if (excl_kernel)
>> +		err = TEST_CODE_READING_NO_ACCESS;
>> +	else
>> +		err = TEST_CODE_READING_OK;
>> +out_err:
>> +	if (evlist) {
>> +		perf_evlist__disable(evlist);
>> +		perf_evlist__munmap(evlist);
>> +		perf_evlist__close(evlist);
>> +		perf_evlist__delete(evlist);
>> +	}
>> +	if (cpus)
>> +		cpu_map__delete(cpus);
>> +	if (threads)
>> +		thread_map__delete(threads);
>> +	machines__destroy_kernel_maps(&machines);
>> +	machine__delete_threads(machine);
>> +	machines__exit(&machines);
>> +
>> +	return err;
>> +}
>> +
>> +int test__code_reading(void)
>> +{
>> +	int ret;
>> +
>> +	ret = do_test_code_reading();
>> +
>> +	switch (ret) {
>> +	case TEST_CODE_READING_OK:
>> +		return 0;
>> +	case TEST_CODE_READING_NO_VMLINUX:
>> +		fprintf(stderr, " (no vmlinux)");
>> +		return 0;
>> +	case TEST_CODE_READING_NO_ACCESS:
>> +		fprintf(stderr, " (no access)");
>> +		return 0;
>> +	default:
>> +		return -1;
>> +	};
>> +}
>> diff --git a/tools/perf/tests/tests.h b/tools/perf/tests/tests.h
>> index 90e3056..fda12266 100644
>> --- a/tools/perf/tests/tests.h
>> +++ b/tools/perf/tests/tests.h
>> @@ -36,5 +36,6 @@ int test__bp_signal_overflow(void);
>>   int test__task_exit(void);
>>   int test__sw_clock_freq(void);
>>   int test__sample_parsing(void);
>> +int test__code_reading(void);
>>
>>   #endif /* TESTS_H */