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I am hoping someone with more experience in Windows 7 can help me out. I have written a php script that utilizes curl_multi to do some spidering. This script runs on an install of WAMP. I originally had this script running on a Windows XP machine but decided to build a faster computer so I could utilize more threads. (The old machine was fairly slow and would max out CPU usage pretty quickly).

I have put together a Windows 7 box with a 6 core AMD 1090T, 16GB of ram and an SSD drive. The new machine is fast and my script WAS running exponentially faster. I was able to dial up the number of threads I was using and get the CPU usage up to about 90% across all cores.

After about an hour or so of running, the CPU usage dropped down to about 16% (every now and then it spikes up to 50%) and the script began running much slower.

I have spent the last 2 days searching the internet for an answer. I have tried disabling my firewall, changing power save modes in the bios, changing power management settings in Windows 7, editing throttling settings in the registry. Somewhere I am missing something. Is the CPU usage being throttled? Are the threads created by this script being throttled? How come it ran fine for that first hour?

Before I uninstall Windows and go with Ubuntu, I am hoping someone has an answer.

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What is the CPU percent usage at this time (when your script is using only 16%)? –  soandos Jan 6 '12 at 3:12
    
16% is the CPU usage, sorry if that was unclear in my post. –  Chris Jan 6 '12 at 3:14
    
Have you tried running the PHP script outside of WAMP? –  kobaltz Jan 6 '12 at 3:23
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~16% just happens to be ~100% /6 Cores, which would be full load for a single threaded application. (just spread across the 6 cores or not). The first thing i would do is run 6X prime (cpu testing) the same way and see if it holds full load. If it does not did threads stop. I dont see anything that confirms that the threads were all still running, and it sounds most like One single hard working thread (16), and other stuff (50) –  Psycogeek Jan 6 '12 at 3:30
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Windows does some weird things. I believe it attempts to determine whether a given application is "foreground" or "background", and that determination is "sticky". Try, eg, going into SystemProperties/Advanced/Performance Settings/Advanced and clicking the "best performance of background services" button. –  Daniel R Hicks Jan 7 '12 at 3:09

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