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Subject: Re: What is wrong with FreeBSD and USB Support
To: Markus Rechberger <mrechberger@gmail.com>
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Cc: freebsd-multimedia@freebsd.org
From: Hans Petter Selasky <hps@selasky.org>
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Date: Mon, 6 Mar 2017 12:40:48 +0100
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Hi,

On 03/06/17 12:36, Markus Rechberger wrote:
> libusb20 - usb userspace interface - usb - roundtrip problem that
> causes this high latency.

If you are using an old FreeBSD kernel, more than two years old, there 
was an issue where malloc() was used in the generic IOCTL path. This 
piece has in later versions of FreeBSD been replace with a conditional 
on-stack buffer. If you have this issue you should see high CPU usage on 
one of the CPU cores while doing USB transfers fast.

--HPS