From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1KqCTG-0000Ol-CT for qemu-devel@nongnu.org; Wed, 15 Oct 2008 15:55:50 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1KqCTB-0000Mm-Rf for qemu-devel@nongnu.org; Wed, 15 Oct 2008 15:55:49 -0400 Received: from [199.232.76.173] (port=54301 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1KqCTB-0000Mf-Ek for qemu-devel@nongnu.org; Wed, 15 Oct 2008 15:55:45 -0400 Received: from wolverine02.qualcomm.com ([199.106.114.251]:43483) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_ARCFOUR_SHA1:16) (Exim 4.60) (envelope-from ) id 1KqCTA-0008Th-2S for qemu-devel@nongnu.org; Wed, 15 Oct 2008 15:55:45 -0400 Message-ID: <48F64A71.5070303@qualcomm.com> Date: Wed, 15 Oct 2008 12:54:25 -0700 From: Max Krasnyansky MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH 4/5] uhci: rewrite UHCI emulator, fully async operation with multiple outstanding transactions References: <200810112354.m9BNsXXh060894@saturn.kn-bremen.de> In-Reply-To: <200810112354.m9BNsXXh060894@saturn.kn-bremen.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Juergen Lock Cc: qemu-devel@nongnu.org Hi Juergen, Juergen Lock wrote: > This is whats got committed as r5050, right? It causes a large slowdown > with some linux guests, as posted here: > http://lists.gnu.org/archive/html/qemu-devel/2008-09/msg01201.html > As mentioned the guest I tested was: > sidux-2008-03-ourea-pre1-kde-lite-i386-200809142136.iso > It uses a Linux 2.6.26 kernel, a FreeBSD guest is not affected by the > slowness, could this be related to dynticks? > > Oh and on one box transfers over the emulated usb nic even sometimes > stall, I have to ping the guest's ip for them to continue, and the ping > then loses packets too. Can you please clarify your setup. As I understood, from the thread you mentioned above, you're running Linux 2.6.26 guest on QEMU under FreeBSD host,correct ? And what you're saying is that USB is slow in that configuration. Assuming that I got that part correctly let me first say that this means that usb-linux is not activated and you're using built-in QEMU USB devices. What this in turn means is that your USB operation is synchronous (all builtin devices are sync). New async logic with multiple transactions, etc only applies to the real USB devices virtualized via usb-linux & libusb. After doing UHCI rewrite I made sure that new code generates exactly the same UHCI structures as the old code. I may have missed something but in general guests should not be affected, and as I explained new async logic does not even kick in with built-in devices. Is there any chance that there may be something else going on here ? In other words are you sure that it's UHCI changes that cause the slow down. If you are sure can you please recompile hw/usb-uhci.c with DEBUG enabled. Save the trace it generates and send it to me. I can take a look at it and see if there is something obvious. I do not have FreeBSD hosts around to try and reproduce this myself. Thanx Max