From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juergen Gross Subject: Re: pvUSB backend performance Date: Thu, 25 Jun 2015 05:36:04 +0200 Message-ID: <558B7724.20402@suse.com> References: <558A9D2A.2020006@suse.com> <20150624135732.GC2742@l.oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150624135732.GC2742@l.oracle.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Konrad Rzeszutek Wilk Cc: "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On 06/24/2015 03:57 PM, Konrad Rzeszutek Wilk wrote: > On Wed, Jun 24, 2015 at 02:06:02PM +0200, Juergen Gross wrote: >> Hi, >> >> my qemu integrated pvUSB backend is now running stable enough to do >> some basic performance measurements. I've passed a memory-stick with >> about 90MB of data on it to a pv-domU. Then I read all the data on >> it with tar and looked how long this would take (elapsed time): >> >> in dom0: 5.2s >> in domU with kernel backend: 6.1s >> in domU with qemu backend: 8.2s >> >> So the qemu backend is about 30% slower than the kernel backend. Is >> this acceptable? > > That sounds about right. I remember seeing (two years ago?) an demonstration > by kraxel where he was doing USB camera in a guest. He pointed out > that USB1 (which is default one in QEMU) implementation sucks as QEMU > has to poll for the commands every time. The XHCI implementation is > better as it has some better API, or such (-EFORGOT). > > Oh, this has more details: > https://www.kraxel.org/blog/2014/03/qemu-and-usb-tablet-cpu-consumtion/ This should be no problem in my case. I'm using libusb, so there is no host adapter emulation active in qemu. Juergen