![](/img/trans.png)
[英]Why time.sleep() delay doesn't work as intended inside the nested while loop?
[英]Why doesn't SIGVTALRM trigger inside time.sleep()?
我正在嘗試使用SIGVTALRM
快照配置文件我的Python代碼,但它似乎沒有觸發阻塞操作,如time.sleep()
和套接字操作。
這是為什么? 有沒有辦法解決這個問題,所以我可以在阻止操作時收集樣本?
我也嘗試過使用ITIMER_PROF
/ SIGPROF
和ITIMER_REAL
/ SIGALRM
,兩者似乎都產生了類似的結果。
我正在測試的代碼如下,輸出類似於:
$ python profiler-test.py
<module>(__main__:1);test_sampling_profiler(__main__:53): 1
<module>(__main__:1);test_sampling_profiler(__main__:53);busyloop(__main__:48): 1509
請注意, timesleep
不顯示時間timesleep
功能。
測試代碼:
import time
import signal
import collections
class SamplingProfiler(object):
def __init__(self, interval=0.001, logger=None):
self.interval = interval
self.running = False
self.counter = collections.Counter()
def _sample(self, signum, frame):
if not self.running:
return
stack = []
while frame is not None:
formatted_frame = "%s(%s:%s)" %(
frame.f_code.co_name,
frame.f_globals.get('__name__'),
frame.f_code.co_firstlineno,
)
stack.append(formatted_frame)
frame = frame.f_back
formatted_stack = ';'.join(reversed(stack))
self.counter[formatted_stack] += 1
signal.setitimer(signal.ITIMER_VIRTUAL, self.interval, 0)
def start(self):
if self.running:
return
signal.signal(signal.SIGVTALRM, self._sample)
signal.setitimer(signal.ITIMER_VIRTUAL, self.interval, 0)
self.running = True
def stop(self):
if not self.running:
return
self.running = False
signal.signal(signal.SIGVTALRM, signal.SIG_IGN)
def flush(self):
res = self.counter
self.counter = collections.Counter()
return res
def busyloop():
start = time.time()
while time.time() - start < 5:
pass
def timesleep():
time.sleep(5)
def test_sampling_profiler():
p = SamplingProfiler()
p.start()
busyloop()
timesleep()
p.stop()
print "\n".join("%s: %s" %x for x in sorted(p.flush().items()))
if __name__ == "__main__":
test_sampling_profiler()
不知道為什么time.sleep會以這種方式工作(它可以使用SIGALRM來知道何時恢復嗎?)但是Popen.wait不會阻止信號,所以最糟糕的情況是你可以調用OS睡眠。
另一種方法是使用單獨的線程來觸發采樣:
import sys
import threading
import time
import collections
class SamplingProfiler(object):
def __init__(self, interval=0.001):
self.interval = interval
self.running = False
self.counter = collections.Counter()
self.thread = threading.Thread(target=self._sample)
def _sample(self):
while self.running:
next_wakeup_time = time.time() + self.interval
for thread_id, frame in sys._current_frames().items():
if thread_id == self.thread.ident:
continue
stack = []
while frame is not None:
formatted_frame = "%s(%s:%s)" % (
frame.f_code.co_name,
frame.f_globals.get('__name__'),
frame.f_code.co_firstlineno,
)
stack.append(formatted_frame)
frame = frame.f_back
formatted_stack = ';'.join(reversed(stack))
self.counter[formatted_stack] += 1
sleep_time = next_wakeup_time - time.time()
if sleep_time > 0:
time.sleep(sleep_time)
def start(self):
if self.running:
return
self.running = True
self.thread.start()
def stop(self):
if not self.running:
return
self.running = False
def flush(self):
res = self.counter
self.counter = collections.Counter()
return res
def busyloop():
start = time.time()
while time.time() - start < 5:
pass
def timesleep():
time.sleep(5)
def test_sampling_profiler():
p = SamplingProfiler()
p.start()
busyloop()
timesleep()
p.stop()
print "\n".join("%s: %s" %x for x in sorted(p.flush().items()))
if __name__ == "__main__":
test_sampling_profiler()
這樣做的結果是:
$ python profiler-test.py
<module>(__main__:1);test_sampling_profiler(__main__:62);busyloop(__main__:54): 2875
<module>(__main__:1);test_sampling_profiler(__main__:62);start(__main__:37);start(threading:717);wait(threading:597);wait(threading:309): 1
<module>(__main__:1);test_sampling_profiler(__main__:62);timesleep(__main__:59): 4280
仍然不完全公平,但在睡眠期間完全沒有樣品。
sleep()
期間缺少SIGVTALRM並不讓我感到驚訝,因為ITIMER_VIRTUAL “ 僅在進程執行時才運行。 ” (另外,非Windows平台上的CPython在select()
方面實現time.sleep()
select()
。)
然而,使用普通的SIGALRM,我預計會出現信號中斷,實際上我會觀察到一個:
<module>(__main__:1);test_sampling_profiler(__main__:62);busyloop(__main__:54): 4914
<module>(__main__:1);test_sampling_profiler(__main__:62);timesleep(__main__:59): 1
我有點改變了代碼,但是你明白了:
class SamplingProfiler(object):
TimerSigs = {
signal.ITIMER_PROF : signal.SIGPROF,
signal.ITIMER_REAL : signal.SIGALRM,
signal.ITIMER_VIRTUAL : signal.SIGVTALRM,
}
def __init__(self, interval=0.001, timer = signal.ITIMER_REAL): # CHANGE
self.interval = interval
self.running = False
self.counter = collections.Counter()
self.timer = timer # CHANGE
self.signal = self.TimerSigs[timer] # CHANGE
....
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.