linux-kernel - Re: [PATCH v2] Add support for usbfs zerocopy.

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Date:	Fri, 8 Jan 2016 23:00:54 -0500
From:	Lingzhu Xiang <lingzhu.xiang@...l.utoronto.ca>
To:	"Steinar H. Gunderson" <sesse@...gle.com>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>
Subject: Re: [PATCH v2] Add support for usbfs zerocopy.

On Wed, Nov 25, 2015 at 7:19 PM, Steinar H. Gunderson <sesse@...gle.com> wrote:
> Add a new interface for userspace to preallocate memory that can be
> used with usbfs. This gives two primary benefits:

Extended testing over one hour shows significant improved CPU usage
and stability:
The old CPU usage is about 12% +/- 5%. The new CPU usage is 4% +/- 1%.

The setup is an i7-4600U laptop running Kinect v2 with 260MB/s
isochronous and 20MB/s bulk transfers.

The improvement in reducing jitter is particularly preferable to
Kinect v2 driver because the isochronous data is structured and one
packet lost means discarding a lot of data.

Regards,
Lingzhu