From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:37575) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QMO9A-0003dK-O3 for qemu-devel@nongnu.org; Tue, 17 May 2011 13:33:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QMO99-0007hU-N6 for qemu-devel@nongnu.org; Tue, 17 May 2011 13:33:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47017) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QMO99-0007hN-DS for qemu-devel@nongnu.org; Tue, 17 May 2011 13:33:27 -0400 Message-ID: <4DD2B21D.8040502@redhat.com> Date: Tue, 17 May 2011 19:36:29 +0200 From: Hans de Goede MIME-Version: 1.0 References: <1305575782-31766-1-git-send-email-kraxel@redhat.com> <1305575782-31766-19-git-send-email-kraxel@redhat.com> <4DD1E1DD.3060605@cisco.com> <4DD221AB.7070009@redhat.com> <4DD26D45.3070309@cisco.com> <4DD27D9D.1050109@cisco.com> <4DD28E0A.2050808@redhat.com> <4DD2AAC6.6060501@cisco.com> In-Reply-To: <4DD2AAC6.6060501@cisco.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 18/18] usb: add ehci adapter List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Ahern Cc: Gerd Hoffmann , qemu-devel@nongnu.org Hi, On 05/17/2011 07:05 PM, David Ahern wrote: > > > On 05/17/11 09:02, Gerd Hoffmann wrote: >> >> Hi, >> >>> (And by the way, where are the focused patches for each, especially the >>> last one - nuking the 8kHz code? >> >> It's squashed in, like everything else. >> >>> We know that it worked on linux and >>> that printers, scanners and storage devices worked ok (mostly). >> >> 8 kHz is insane. >> >> I looked closely while trying to make 8 kHz a runtime option instead of >> a compile time option, then decided to drop it altogether as it is >> totally pointless. qemu simply can't handle that wakeup rate. It maxed >> out at ~3 kHz wakeups in my tests. And it burns tons of CPU time. > > Our mileage varies. While CPU usage was high (30%'ish) when the device > was in use, the controller was stopped when devices are not accessed. > All in all my laptop was billowing smoke while using it. > >> >> I also don't see what it would buy us. We can wakeup with 1 kHz rate >> (maybe even lower), then emulate 8 (or more) microframes each time. > > How much time have you spent looking at isochronous devices (web cams, > audio streaming, iphones)? Your positive that the 8k code will not be > needed for it? Very likely it won't be needed both the guest OS, as well as any emulated hardware (or redirection code) will be doing some amount of buffering. Normal bufferering for usb video devices is 32 iso packets per urb and then 2-4 queued urbs, so that means that the OS does not even ask to be bothered with iso transfers till 32 of them have completed, or in other words 4 ms have passed in the usb 2 case with an endpoint with the lowest possible interval. Regards, Hans