目錄
- 概述
- 源碼解析
- 1. atrace-進程打樁端
- 1.1 vold進程中對atrace的使用
- 1.2 atrace_set_tracing_enabled-設置atrace_is_enabled變量，設置atrace_enabled_tags
- 1.3 atrace_update_tags-如果atrace_is_enabled為true則atrace_enabled_tags為debug.atrace.tags.enableflags屬性值否則為ATRACE_TAG_NOT_READY
- 1.4 atrace_get_property-獲取debug.atrace.tags.enableflags的值，默認為ATRACE_TAG_ALWAYS
- 1.5 atrace_is_app_tracing_enabled-進程名字和debug.atrace.app_%d屬性值匹配
- 1.6 atrace_is_cmdline_match-進程名字和debug.atrace.app_%d屬性值匹配
- 1.7 ATRACE_BEGIN-初始化atrace並寫trace信息
- 1.8 ATRACE_ENABLED-atrace_is_tag_enabled-初始化atrace
- 1.9 atrace_get_enabled_tags-初始化atrace，更新tags
- 1.10 atrace_init-初始化atrace，更新tags
- 1.11 atrace_seq_number_changed-初始化atrace，更新tags
- 1.12 atrace_init_once-打開trace_marker文件初始化atrace
- 1.13 atrace_begin_body-寫到trace_marker文件中
- 1.14 WRITE_MSG-寫到trace_marker文件中
- 2. atrace-數據采集端
- 3. ftrace
- 1. atrace-進程打樁端
- systrace工具的使用
- 問題
- 補充
- 參考
概述
ftrace：是一個內核函數跟蹤器，function tracer，旨在幫助開發人員和系統設計者可以找到內核內部發生的事情。
atrace：Android tracer，使用ftrace來跟蹤Android上層的函數調用。為數據采集部分
systrace：Android的trace數據分析工具，將atrace采集上來的數據，以圖形化的方式展現出來。
源碼解析
1. atrace-進程打樁端
主要為android/system/core/libcutils/trace-dev.cpp和trace-dev.inc文件
#define ATRACE_TAG ATRACE_TAG_PACKAGE_MANAGER // 定義tags，這里屬於pm類，就是抓systrace的時候：python systrace.py -o mynewtrace.html pm 所選擇的pm類
ATRACE_BEGIN("VoldNativeService::start"); // 往/sys/kernel/debug/tracing/trace_marker文件寫一個時間點
ATRACE_END(); // 結束的時候，又寫一個時間點
中間的trace文件生成
<unknown>-4668 ( 4668) [001] .... 201.584372: tracing_mark_write: B|4668|main
<unknown>-4668 ( 4668) [001] .... 201.594438: tracing_mark_write: B|4668|VolumeManager::start
<unknown>-4668 ( 4668) [001] .... 201.594459: tracing_mark_write: B|4668|VolumeManager::unmountAll()
<unknown>-4668 ( 4668) [001] .... 201.601562: tracing_mark_write: E|4668
<unknown>-4668 ( 4668) [001] .... 201.601578: tracing_mark_write: B|4668|Devmapper::destroyAll
<unknown>-4668 ( 4668) [001] .... 201.602094: tracing_mark_write: E|4668
<unknown>-4668 ( 4668) [001] .... 201.602110: tracing_mark_write: B|4668|Loop::destroyAll
<unknown>-4668 ( 4668) [001] .... 201.604609: tracing_mark_write: E|4668
<unknown>-4668 ( 4668) [001] .... 201.604988: tracing_mark_write: B|4668|VolumeManager::updateVirtualDisk
<unknown>-4668 ( 4668) [001] .... 201.605140: tracing_mark_write: E|4668
<unknown>-4668 ( 4668) [001] .... 201.605147: tracing_mark_write: E|4668
<unknown>-4668 ( 4668) [001] .... 201.605153: tracing_mark_write: B|4668|process_config
<unknown>-4668 ( 4668) [001] .... 201.607640: tracing_mark_write: E|4668
<unknown>-4668 ( 4668) [001] .... 201.607880: tracing_mark_write: B|4668|VoldNativeService::start
<unknown>-4668 ( 4668) [001] .... 201.609138: tracing_mark_write: E|4668
<unknown>-4668 ( 4668) [001] .... 201.609334: tracing_mark_write: B|4668|NetlinkManager::start
<unknown>-4668 ( 4668) [001] .... 201.609720: tracing_mark_write: E|4668
<unknown>-4668 ( 4668) [003] .... 201.610778: tracing_mark_write: B|4668|coldboot
<unknown>-4670 ( 4668) [000] .... 201.647880: tracing_mark_write: B|4668|setListener
<unknown>-4670 ( 4668) [000] .... 201.647894: tracing_mark_write: E|4668
<unknown>-4670 ( 4668) [000] .... 201.649346: tracing_mark_write: B|4668|unmount
<unknown>-4670 ( 4668) [000] .... 201.649660: tracing_mark_write: E|4668
1.1 vold進程中對atrace的使用
int main(int argc, char** argv) {
// 設置atrace_enabled_tags = ATRACE_TAG_NOT_READY;
// 設置atrace_is_enabled為false，相當於是關閉atrace
// 需要將atrace_set_tracing_enabled設為true，打開systrace，選擇pm項，才會抓到
atrace_set_tracing_enabled(false);
。。。。
ATRACE_BEGIN("VoldNativeService::start");
if (android::vold::VoldNativeService::start() != android::OK) {
LOG(ERROR) << "Unable to start VoldNativeService";
exit(1);
}
ATRACE_END();
LOG(DEBUG) << "VoldNativeService::start() completed OK";
ATRACE_BEGIN("NetlinkManager::start");
if (nm->start()) {
PLOG(ERROR) << "Unable to start NetlinkManager";
exit(1);
}
ATRACE_END();
// This call should go after listeners are started to avoid
// a deadlock between vold and init (see b/34278978 for details)
android::base::SetProperty("vold.has_adoptable", has_adoptable ? "1" : "0");
android::base::SetProperty("vold.has_quota", has_quota ? "1" : "0");
android::base::SetProperty("vold.has_reserved", has_reserved ? "1" : "0");
// Do coldboot here so it won't block booting,
// also the cold boot is needed in case we have flash drive
// connected before Vold launched
coldboot("/sys/block");
ATRACE_END();
。。。
}
1.2 atrace_set_tracing_enabled-設置atrace_is_enabled變量，設置atrace_enabled_tags
void atrace_set_tracing_enabled(bool enabled)
{
atomic_store_explicit(&atrace_is_enabled, enabled, memory_order_release);
atrace_update_tags();
}
1.3 atrace_update_tags-如果atrace_is_enabled為true則atrace_enabled_tags為debug.atrace.tags.enableflags屬性值否則為ATRACE_TAG_NOT_READY
// Update tags if tracing is ready. Useful as a sysprop change callback.
void atrace_update_tags()
{
uint64_t tags;
// 為true，走這里
if (atomic_load_explicit(&atrace_is_enabled, memory_order_acquire)) {
// 獲取debug.atrace.tags.enableflags的值，默認為ATRACE_TAG_ALWAYS，或者加上APP
tags = atrace_get_property();
pthread_mutex_lock(&atrace_tags_mutex);
atrace_enabled_tags = tags;
pthread_mutex_unlock(&atrace_tags_mutex);
} else {
// Tracing is disabled for this process, so we simply don't
// initialize the tags.
pthread_mutex_lock(&atrace_tags_mutex);
// 第63位為1
atrace_enabled_tags = ATRACE_TAG_NOT_READY;
pthread_mutex_unlock(&atrace_tags_mutex);
}
}
1.4 atrace_get_property-獲取debug.atrace.tags.enableflags的值，默認為ATRACE_TAG_ALWAYS
// Read the sysprop and return the value tags should be set to
static uint64_t atrace_get_property()
{
char value[PROPERTY_VALUE_MAX];
char *endptr;
uint64_t tags;
property_get("debug.atrace.tags.enableflags", value, "0");
errno = 0;
tags = strtoull(value, &endptr, 0);
if (value[0] == '\0' || *endptr != '\0') {
ALOGE("Error parsing trace property: Not a number: %s", value);
return 0;
} else if (errno == ERANGE || tags == ULLONG_MAX) {
ALOGE("Error parsing trace property: Number too large: %s", value);
return 0;
}
// Only set the "app" tag if this process was selected for app-level debug
// tracing.
if (atrace_is_app_tracing_enabled()) {
// 匹配的話，tags就有APP，APP的是第12位為1
tags |= ATRACE_TAG_APP;
} else {
tags &= ~ATRACE_TAG_APP;
}
// ATRACE_TAG_VALID_MASK表示前26位都為1，ATRACE_TAG_ALWAYS表示第1位為1
return (tags | ATRACE_TAG_ALWAYS) & ATRACE_TAG_VALID_MASK;
}
1.5 atrace_is_app_tracing_enabled-進程名字和debug.atrace.app_%d屬性值匹配
// Determine whether application-level tracing is enabled for this process.
static bool atrace_is_app_tracing_enabled()
{
bool sys_debuggable = property_get_bool("ro.debuggable", 0);
bool result = false;
if (sys_debuggable || atrace_is_debuggable) {
// Check whether tracing is enabled for this process.
FILE * file = fopen("/proc/self/cmdline", "re");
if (file) {
char cmdline[4096];
if (fgets(cmdline, sizeof(cmdline), file)) {
// 進程名字和debug.atrace.app_%d屬性值匹配，debug.atrace.app_%d屬性值可為*
result = atrace_is_cmdline_match(cmdline);
} else {
ALOGE("Error reading cmdline: %s (%d)", strerror(errno), errno);
}
fclose(file);
} else {
ALOGE("Error opening /proc/self/cmdline: %s (%d)", strerror(errno),
errno);
}
}
return result;
}
1.6 atrace_is_cmdline_match-進程名字和debug.atrace.app_%d屬性值匹配
// Check whether the given command line matches one of the comma-separated
// values listed in the app_cmdlines property.
static bool atrace_is_cmdline_match(const char* cmdline)
{
int count = property_get_int32("debug.atrace.app_number", 0);
char buf[PROPERTY_KEY_MAX];
char value[PROPERTY_VALUE_MAX];
for (int i = 0; i < count; i++) {
snprintf(buf, sizeof(buf), "debug.atrace.app_%d", i);
property_get(buf, value, "");
if (strcmp(value, "*") == 0 || strcmp(value, cmdline) == 0) {
return true;
}
}
return false;
}
1.7 ATRACE_BEGIN-初始化atrace並寫trace信息
// vold中定義#define ATRACE_TAG ATRACE_TAG_PACKAGE_MANAGER，屬於pm
#define ATRACE_BEGIN(name) atrace_begin(ATRACE_TAG, name)
static inline void atrace_begin(uint64_t tag, const char* name)
{// 為false，則打印
if (CC_UNLIKELY(atrace_is_tag_enabled(tag))) {
void atrace_begin_body(const char*);
// 走這里
atrace_begin_body(name);
}
}
1.8 ATRACE_ENABLED-atrace_is_tag_enabled-初始化atrace
#define ATRACE_ENABLED() atrace_is_tag_enabled(ATRACE_TAG)
static inline uint64_t atrace_is_tag_enabled(uint64_t tag)
{// atrace_get_enabled_tags返回為ATRACE_TAG_ALWAYS，vold的話，tag就是pm，所以這里false
return atrace_get_enabled_tags() & tag;
}
1.9 atrace_get_enabled_tags-初始化atrace，更新tags
uint64_t atrace_get_enabled_tags()
{
atrace_init();
return atrace_enabled_tags;
}
1.10 atrace_init-初始化atrace，更新tags
void atrace_init() {
#if defined(__BIONIC__)
// 獲取__system_property_serial，用來判斷屬性更新的
uint32_t seq_no = __system_property_serial(atrace_property_info); // Acquire semantics.
#else
uint32_t seq_no = 0;
#endif
uint32_t prev_seq_no = atomic_load_explicit(&last_sequence_number, memory_order_relaxed);
// 如果屬性更新了
if (CC_UNLIKELY(seq_no != prev_seq_no)) {
// 初始化atrace，更新tags
atrace_seq_number_changed(prev_seq_no, seq_no);
}
}
1.11 atrace_seq_number_changed-初始化atrace，更新tags
static void atrace_seq_number_changed(uint32_t prev_seq_no, uint32_t seq_no) {
// atrace_is_enabled的值為false，直接返回了；它默認是true的，如果不設置的話，默認是可以抓trace的
if (!atomic_load_explicit(&atrace_is_enabled, memory_order_acquire)) {
return;
}
// Someone raced us.
if (!atomic_compare_exchange_strong(&last_sequence_number, &prev_seq_no, seq_no)) {
return;
}
if (CC_UNLIKELY(prev_seq_no == kSeqNoNotInit)) {
#if defined(__BIONIC__)
const prop_info* new_pi = __system_property_find("debug.atrace.tags.enableflags");
if (new_pi) atrace_property_info = new_pi;
#endif
// 在這里調用atrace_init_once函數，打開trace_marker文件初始化atrace
pthread_once(&atrace_once_control, atrace_init_once);
}
// 更新tags
atrace_update_tags();
}
1.12 atrace_init_once-打開trace_marker文件初始化atrace
static void atrace_init_once()
{
atrace_marker_fd = open("/sys/kernel/debug/tracing/trace_marker", O_WRONLY | O_CLOEXEC);
if (atrace_marker_fd == -1) {
atrace_marker_fd = open("/sys/kernel/tracing/trace_marker", O_WRONLY | O_CLOEXEC);
}
if (atrace_marker_fd == -1) {
ALOGE("Error opening trace file: %s (%d)", strerror(errno), errno);
atrace_enabled_tags = 0;
} else {
atrace_enabled_tags = atrace_get_property();
}
}
1.13 atrace_begin_body-寫到trace_marker文件中
void atrace_begin_body(const char* name)
{
WRITE_MSG("B|%d|", "%s", name, "");
}
1.14 WRITE_MSG-寫到trace_marker文件中
#define WRITE_MSG(format_begin, format_end, name, value) { \
char buf[ATRACE_MESSAGE_LENGTH] __attribute__((uninitialized)); \
int pid = getpid(); \
int len = snprintf(buf, sizeof(buf), format_begin "%s" format_end, pid, \
name, value); \
if (len >= (int) sizeof(buf)) { \
/* Given the sizeof(buf), and all of the current format buffers, \
* it is impossible for name_len to be < 0 if len >= sizeof(buf). */ \
int name_len = strlen(name) - (len - sizeof(buf)) - 1; \
/* Truncate the name to make the message fit. */ \
ALOGW("Truncated name in %s: %s\n", __FUNCTION__, name); \
len = snprintf(buf, sizeof(buf), format_begin "%.*s" format_end, pid, \
name_len, name, value); \
} \
write(atrace_marker_fd, buf, len); \
}
2. atrace-數據采集端
3. ftrace
systrace工具的使用
1. 使用adb的systrace工具
該命令在android-sdk/platform-tools/systrace/中，需要安裝python
python systrace.py -o mynewtrace.html sched freq idle am wm gfx view binder_driver hal dalvik camera input res
python systrace.py --list-categories 列出支持的策略
也可以使用android-studio中的monitor.bat工具來抓systrace
2. 使用perfetto工具或者開發者選項打開
perfetto -o /data/misc/perfetto-traces/trace -t 10s sched freq idle am wm gfx view
也可以在開發者選項中，打開System Tracing，源碼在android/packages/apps/Traceur，用的也是perfetto工具
打開開關，就可以抓trace了
然后可以使用android-sdk/platform-tools/systrace/中的systrace工具，轉成網頁形式的
python systrace.py --from-file=trace
轉換的過程中，會有錯誤：這是因為如果不是adb形式的，它是沒有開頭和結尾的，所以不需要辨認了，直接把讀到的data傳進去就好了
data_start = re.search(TRACE_START_REGEXP, result).end(0)
AttributeError: 'NoneType' object has no attribute 'end'
def _read_trace_data(self):
with open(self._filename, 'rb') as f:
result = f.read()
try:
data_start = re.search(TRACE_START_REGEXP, result).end(0)
data = re.sub(ADB_IGNORE_REGEXP, '', result[data_start:])
except:
data = result
return self._preprocess_data(data)
問題
1. perfetto文件轉html出錯
Reading results from file.
Tracing completed. Collecting output...
Traceback (most recent call last):
File "systrace.py", line 49, in <module>
sys.exit(run_systrace.main())
File "/home/a/Downloads/platform-tools/systrace/catapult/systrace/systrace/run_systrace.py", line 205, in main
main_impl(sys.argv)
File "/home/a/Downloads/platform-tools/systrace/catapult/systrace/systrace/run_systrace.py", line 200, in main_impl
controller.StopTracing()
File "/home/a/Downloads/platform-tools/systrace/catapult/systrace/systrace/systrace_runner.py", line 49, in StopTracing
self._tracing_controller.StopTracing()
File "/home/a/Downloads/platform-tools/systrace/catapult/systrace/systrace/tracing_controller.py", line 187, in StopTracing
if agent.StopAgentTracing(timeout=self._controller_config.timeout):
File "/home/a/Downloads/platform-tools/systrace/catapult/common/py_utils/py_utils/__init__.py", line 103, in RunWithTimeout
return timeout_retry.Run(func, timeout, 0, args=args)
File "/home/a/Downloads/platform-tools/systrace/catapult/systrace/systrace/../../devil/devil/utils/timeout_retry.py", line 164, in Run
error_log_func=error_log_func)
File "/home/a/Downloads/platform-tools/systrace/catapult/systrace/systrace/../../devil/devil/utils/reraiser_thread.py", line 199, in JoinAll
self._JoinAll(watcher, timeout)
File "/home/a/Downloads/platform-tools/systrace/catapult/systrace/systrace/../../devil/devil/utils/reraiser_thread.py", line 171, in _JoinAll
thread.ReraiseIfException()
File "/home/a/Downloads/platform-tools/systrace/catapult/systrace/systrace/../../devil/devil/utils/reraiser_thread.py", line 94, in run
self._ret = self._func(*self._args, **self._kwargs)
File "/home/a/Downloads/platform-tools/systrace/catapult/systrace/systrace/../../devil/devil/utils/timeout_retry.py", line 156, in <lambda>
lambda: func(*args, **kwargs), name=thread_name)
File "/home/a/Downloads/platform-tools/systrace/catapult/systrace/systrace/tracing_agents/atrace_from_file_agent.py", line 104, in StopAgentTracing
self._trace_data = self._read_trace_data()
File "/home/a/Downloads/platform-tools/systrace/catapult/systrace/systrace/tracing_agents/atrace_from_file_agent.py", line 120, in _read_trace_data
data_start = re.search(TRACE_START_REGEXP, result).end(0)
AttributeError: 'NoneType' object has no attribute 'end'
解決辦法：
systrace/systrace/tracing_agents/atrace_from_file_agent.py文件：加個異常處理，就可以轉為html文件了
def _read_trace_data(self):
with open(self._filename, 'rb') as f:
result = f.read()
try:
data_start = re.search(TRACE_START_REGEXP, result).end(0)
data = re.sub(ADB_IGNORE_REGEXP, '', result[data_start:])
except:
data = result
return self._preprocess_data(data)
補充
參考
1. Android Systrace 基礎知識 -- Systrace 簡介
https://www.androidperformance.com/2019/05/28/Android-Systrace-About/
2. ftrace - Function Tracer - 內核文檔
https://www.kernel.org/doc/Documentation/trace/ftrace.txt