From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:47244) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TOPQS-00027Z-8D for qemu-devel@nongnu.org; Wed, 17 Oct 2012 04:56:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TOPQM-00080e-Le for qemu-devel@nongnu.org; Wed, 17 Oct 2012 04:56:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:17096) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TOPQM-00080U-DQ for qemu-devel@nongnu.org; Wed, 17 Oct 2012 04:56:22 -0400 Message-ID: <507E72B3.2010003@redhat.com> Date: Wed, 17 Oct 2012 10:56:19 +0200 From: Gerd Hoffmann MIME-Version: 1.0 References: <507E6F32.4070009@msgid.tls.msk.ru> In-Reply-To: <507E6F32.4070009@msgid.tls.msk.ru> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] udev 42-qemu-usb.rules considered harmful? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Michael Tokarev Cc: qemu-devel On 10/17/12 10:41, Michael Tokarev wrote: > Hello. > > I noticed that "some" versions of linux guests shows quite What is "some"? > As far as I can see, this rule is to reduce polling interrupt > frequency, but apparently it does not help: any usb device > connected to guest, and the host CPU usage rises anyway, with > or without this rule. No, it is for suspending the usb bus, so qemu stops doing 1000 wakeups per second when the usb tablet is idle. Works only in case all devices on the usb bus support it, but for the typical usb use case (-usbdevice tablet for the abs ptr) this is the case. > Now the question: should we remove this rule? No. We should fix whatever is broken. > Why it is needed > to start with? See above. cheers, Gerd