为什么python没有垃圾收集器线程？ [英] Why python doesn't have Garbage Collector thread?

问题描述

Java有daemon线程来监视内存使用情况并执行gc任务。从jstack中我可以看到

$ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $'$'$ ]
java.lang.Thread.sleep的
（原生方法）
....
GC任务线程＃
java.lang.Thread.State：TIMED_WAITING（sleeping） 0（ParallelGC）os_prio = 0 tid = 0x00007f34b0023000 nid = 0x809 runnable
GC任务线程＃1（ParallelGC）os_prio = 0 tid = 0x00007f34b0024800 nid = 0x80a可运行
GC任务线程＃2 ParallelGC）os_prio = 0 tid = 0x00007f34b0026800 nid = 0x80b runnable

但是在谈到python时，我写了一篇

$ b $ pre $ ＃！/ usr / bin / env python
导入gc
导入时间
gc .enable（）
，而True：
print每分钟打印一次。
time.sleep（60）


我看到python进程只有一个线程，

  $ cat / proc / 1627 / status 
名称：python 
 ... 
线程：1 
  

问题是，为什么python没有像Java那样的gc线程？然后哪个线程执行gc任务？

解决方案

如果您使用 -XX启动java：+ UseSerialGC 选项，您将看不到任何GC线程。
对于单线程GC算法，应用程序线程可用于执行GC活动。

所需的专用线程

并行GC（您需要多于单线程）

并行GC（与应用程序逻辑并行运行的GC活动）

Java has daemon thread to monitor memory usage and do the gc task. From jstack I see

"main" #1 prio=5 os_prio=0 tid=0x00007f34b000e000 nid=0x808 waiting on condition [0x00007f34b6f02000]
   java.lang.Thread.State: TIMED_WAITING (sleeping)
    at java.lang.Thread.sleep(Native Method)
....
"GC task thread#0 (ParallelGC)" os_prio=0 tid=0x00007f34b0023000 nid=0x809 runnable 
"GC task thread#1 (ParallelGC)" os_prio=0 tid=0x00007f34b0024800 nid=0x80a runnable 
"GC task thread#2 (ParallelGC)" os_prio=0 tid=0x00007f34b0026800 nid=0x80b runnable

But speaking of python, I wrote a

#!/usr/bin/env python
import gc
import time 
gc.enable()
while True:
    print "This prints once a minute."
    time.sleep(60) 

I saw the the python process has only one thread,

$ cat /proc/1627/status
Name:   python
...
Threads:    1

The question is, why python doesn't have gc thread like Java? Then which thread does the gc task?

解决方案

If you start java with -XX:+UseSerialGC options you will not see any GC thread. For single threaded GC algorithm application thread can be used to do GC activities.

Dedicated threads required for

• Parallel GC (you need more than single thread)
• Concurrent GC (GC activities running in parallel with application logic)

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