Re: [Libusb-win32-devel] performance

[Stephan M. <ste...@we...>]

I tried the same on my system (WinXP, 2GHz CPU) and my test program
(code attached) consumes less than 5% of CPU resources.

But if I enable debugging by calling usb_set_debug(4) and if I connect
a tool such as DebugView to capture the debug messages then CPU
load goes up to 80%.

Try to disable debug messages by calling usb_set_debug(0) after usb_init().

My test program also calls usb_find_devices() from a seperate thread and
it doesn't crash (as you mentioned in your other mail). If I unplug my device
then the application just terminates. 
The current DLL isn't fully thread safe but refreshing the device list from
a second thread shouldn't crash the DLL.

Which version of the DLL are you using? Have you tried one of the latest
development versions?

Stephan

> 
> Hi,
> 
> 
> I'm encountering performance problems. The code below runs on a linux system with for abot 1400 cycles per second, not consuming a lot of CPU. This is near the theoretic maximum. Under windows it runs at less than 800 cycles, taking 70% of the CPU, mostly kernel times. Any ideas.
> 
> 
> for (;;) {
> 
>         while (usb_interrupt_read(MyHandle, 0x88, (char*)Buffer, sizeof(Buffer), 1000) < 0) ;
> 
>         // build Command
> 
>         usb_interrupt_write(MyHandle, 0x04, (char*)Command, 5, 1000);
> 
> }
> 
> 
> Thanks,
> 
> Steffen
> 
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