Re: [libusb] libusb task utilization

[Tim R. <ti...@pr...>]

Doak, Roger (GE Healthcare) wrote:
>  
>
> We are using Libusb 1.0.9 on a Linux platform.  Our host is using
> Asynchronous device I/O and interrupt transfer.  We have a dedicated
> high priority task that calls libusb handle events.  When a device is
> connected eight 64 byte buffers are submitted to ensure the library
> always has a buffer to write incoming data into.  The host can have up
> to 8 USB devices connected.  We wanted to ensure we had enough CPU to
> handle all 8 simultaneously so we programed the USB devices to send
> 506 bytes at 120Hz (these will be segmented into seven 64 byte packets
> and one 58 byte packet).
>

What are your latency requirements?  If your fundamental transfers will
always be 506 bytes, then make your buffers 512 bytes instead of 64. 
That will reduce the kernel/user/kernel transition overhead by a factor
of 8.

-- 
Tim Roberts, ti...@pr...
Providenza & Boekelheide, Inc.