From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Smith Subject: Re: Paravirtualised drivers for fully virtualised domains, rev9 Date: Sat, 12 Aug 2006 09:32:23 +0100 Message-ID: <20060812083223.GA2029@cam.ac.uk> References: <20060811101704.GA3476@cam.ac.uk> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============0276187459==" Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Mime-version: 1.0 Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Steve Dobbelstein Cc: xen-devel@lists.xensource.com, sos22@srcf.ucam.org List-Id: xen-devel@lists.xenproject.org --===============0276187459== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="cNdxnHkX5QqsyA0e" Content-Disposition: inline --cNdxnHkX5QqsyA0e Content-Type: text/plain; charset=us-ascii Content-Disposition: inline > > > Here is what I have found so far in trying to chase down the cause of > the > > > slowdown. > > > The qemu-dm process is running 99.9% of the CPU on dom0. > > That seems very wrong. When I try this, the device model is almost > > completely idle. Could you see what strace says, please, or if there > > are any strange messages in the /var/log/qemu-dm. file? > Looks like I jumped the gun in relating the 99.9% CPU usage for qemu-dm and > the network. I start up the HVM domain and without running any tests > qemu-dm is chewing up 99.9% of the CPU in dom0. So it appears that the > 100% CPU qemu usage is a problem by itself. Looks like the same problem > Harry Butterworth is seeing. qemu-dm misbehaving could certainly lead to the netif going very slowly. > > 2) How often is the event channel interrupt firing according to > > /proc/interrupts? I see about 50k-150k/second. > I'm seeing ~ 500/s when netpipe-tcp reports decent throughput at smaller > buffer sizes and then ~50/s when the throughput drops at larger buffer > sizes. How large do they have to be to cause problems? > > The other thing is that these drivers seem to be very sensitive to > > kernel debugging options in the domU. If you've got anything enabled > > in the kernel hacking menu it might be worth trying again with that > > switched off. > Kernel debugging is on. I also have Oprofile enabled. I'll build a kernel > without those and see if it helps. Worth a shot. It shouldn't cause the problems with qemu, though. > > > It appears there is some interaction between using the xen-vnif > > > driver and the qemu timer code. I'm still exploring. > > I'd be happier if I could reproduce this problem here. Are you > > running SMP? PAE? 64 bit? What kernel are you running in the domU? > UP kernels in both the domU and dom0 (although the scheduler likes to move > the 1 vcpu in dom0 around to different physical CPUs). 64-bit kernels on > both. I've mostly been testing with 32 bit PAE. I'll have a go with a 64 bit system on Monday. Thanks, Steven. --cNdxnHkX5QqsyA0e Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.3 (GNU/Linux) iD8DBQFE3ZIXO4S8/gLNrjcRApkWAJ9hhBqd1YuX8Q/BArlzV3LU4SKgIQCfVWZu eYC3rJ+wNPDQq5gGL0aJgaY= =e0gT -----END PGP SIGNATURE----- --cNdxnHkX5QqsyA0e-- --===============0276187459== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel --===============0276187459==--