Python on windows - conhost.exe CPU usage

Question

I'm running a Python script on Windows, and I've noticed that even though the Python process takes ~8% CPU, the associated conhost.exe process takes ~14%.

Why is this so? How come such a large part of the CPU consumption is in the conhost and not in the Python process?
Is there a way to reduce this CPU consumption? (besides optimizing the code of course)

UPDATE 1: Win7 64bit, Python 2.6.6

UPDATE 2: The Python program uses a C++ package via SWIG Python bindings. The C++ package (quickfix) does I/O with the network quite a bit (1), it also prints to the console (2). The Python code prints to several files (3). Which if these three should be suspect?

Does the CPU usage in conhost.exe mostly disappear if you minimize the console window? If so, it may be an issue with the video device driver: for example, if you are using the Microsoft generic drivers console performance is sometimes poor. — Harry Johnston, Oct 17 '11 at 00:34

score 3 · Accepted Answer · answered Oct 15 '11 at 13:29

3

Since we don't know what your program is doing we have to guess a little. So long as there is no I/O I'd expect conhost to consume 0% CPU. So I hypothesise that you are printing a lot of text to the console. For example, the following program has the same symptoms as you report:

while True:
    print "Hello world!"

answered Oct 15 '11 at 13:29

David Heffernan

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printing to console is only think that should make conhost work – David Heffernan Oct 16 '11 at 18:49
Following this answer I found that diverting the output to file reduces conhost.exe's CPU consumption dramatically. So you could `script.py > output.txt` or even `script.py > nul` if you don't care to lose the output – Jonathan Livni Oct 17 '11 at 17:19
Nice to see my suspicions confirmed. – David Heffernan Oct 17 '11 at 17:20

Python on windows - conhost.exe CPU usage

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