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I'm using a systhread in my external. In the thread i have an infinite loop calling ReadFile, to call from a USB device. As soon as I add the external to a patch, I can see max using around 94% CPU even though the thread is not necessarily doing anything (e.g. ReadFile unsuccesful).

I'm on Windows XP SP2 Pro and MAX/MSP 4.5.7. Any ideas? Is it just a matter of thread priority?

I'm using a systhread in my external. In the thread i have an infinite loop calling ReadFile, to call from a USB device. As soon as I add the external to a patch, I can see max using around 94% CPU even though the thread is not necessarily doing anything (e.g. ReadFile unsuccesful). 

systhread-readfile-and-cpu-usage

> I'm using a systhread in my external. In the thread i have an 

> infinite loop calling ReadFile, to call from a USB device. As soon 

> as I add the external to a patch, I can see max using around 94% 

> CPU even though the thread is not necessarily doing anything (e.g. 

As is typical in multi-threaded programming using infinite loops, you 

probably want your thread to sleep periodically (systhread_sleep) or 

some other means of thread synchronization with your main thread 

(e.g. condition variables, semaphores, etc.). Otherwise the thread 

will consume 100% CPU. For example the following code, even though it 

If this is confusing, I would highly recommend reading some 

literature on multi-threaded programming. One text book I like is 

"Modern Operating Systems" by Andrew Tanenbaum, but there are also 

> I'm using a systhread in my external. In the thread i have an  
> infinite loop calling ReadFile, to call from a USB device. As soon  
> as I add the external to a patch, I can see max using around 94%  
> CPU even though the thread is not necessarily doing anything (e.g.  
> ReadFile unsuccesful).

As is typical in multi-threaded programming using infinite loops, you  
probably want your thread to sleep periodically (systhread_sleep)  or  
some other means of thread synchronization with your main thread  
(e.g. condition variables, semaphores, etc.). Otherwise the thread  
will consume 100% CPU. For example the following code, even though it  
"does nothing", will use 100% CPU:

If this is confusing, I would highly recommend reading some  
literature on multi-threaded programming. One text book I like is  
"Modern Operating Systems" by Andrew Tanenbaum, but there are also  
lots of articles on the subject online.

systhread, ReadFile and cpu usage