Make Process.wait() busy loop on UNIX a little clever

[giampaolo]

From g.rodola on January 19, 2012 21:35:03

Process.wait(timeout=N) on UNIX is implemented as a busy loop which keeps 
calling os.waitpid() until the process is gone or the timeout is reached.
A time.sleep() call is used to avoid hogging CPU resources: 
https://code.google.com/p/psutil/source/browse/tags/release-0.4.1/psutil/_psposix.py#53
 This is not very smart though, as it keeps sleeping for 0.0001 seconds.
I noticed a better solution used in Lib/subprocess.py which increases the sleep 
interval incrementally, saving a considerable amount of CPU cycles if the 
process dies, say, after 20 seconds: 
http://hg.python.org/cpython/file/053fbceaf789/Lib/subprocess.py#l1407 I think 
it's worth to take that as an example.
Also, we might want to keep an eye on http://bugs.python.org/issue12187 and 
hopefully get rid of the busy loop on some UNIX platforms.

Original issue: http://code.google.com/p/psutil/issues/detail?id=245

[giampaolo]

From g.rodola on January 20, 2012 10:53:25

Fixed in r1252 .

Status: FixedInSVN
Labels: Performance

[giampaolo]

From jlo...@gmail.com on January 20, 2012 12:16:23

I didn't get a chance to review this one; did you put in some kind of safeguard 
upper limit? My only concern would be making the sleep delay too large could 
have a negative impact on functionality.

[giampaolo]

From g.rodola on January 20, 2012 12:19:10

Yep, the limit is 0.04 seconds.

[giampaolo]

From jlo...@gmail.com on January 20, 2012 12:30:11

Excellent, nice find on this one

[giampaolo]

From g.rodola on January 30, 2012 04:19:51

Labels: Milestone-0.5.0

[giampaolo]

From g.rodola on June 27, 2012 11:54:03

0.5.0 is finally out. Closing out as fixed.

Status: Fixed

[giampaolo]

From g.rodola on March 02, 2013 04:06:41

Updated csets after the SVN -> Mercurial migration: r1252 == revision 
18d53ff30011