From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gregory Haskins Subject: Re: Host latency peaks due to kvm-intel Date: Thu, 23 Jul 2009 15:43:25 -0400 Message-ID: <4A68BD5D.1070302@gmail.com> References: <4A68A6E5.6010808@siemens.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig55B498C56C17C035599A340D" Cc: kvm-devel , RT To: Jan Kiszka Return-path: Received: from mail-pz0-f192.google.com ([209.85.222.192]:36577 "EHLO mail-pz0-f192.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751866AbZGWUIx (ORCPT ); Thu, 23 Jul 2009 16:08:53 -0400 In-Reply-To: <4A68A6E5.6010808@siemens.com> Sender: linux-rt-users-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig55B498C56C17C035599A340D Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: quoted-printable Jan Kiszka wrote: > Hi, > > did anyone recently tried current KVM for Intel over some real-time > Linux? I'm seeing more than 500 us latency peaks on the host, > specifically during VM startup. This applies to both 2.6.29.6-rt23 and > Xenomai/I-pipe. For -rt, I both tried the included (patched) KVM module= s > as well as kvm.git head with some additionally required -rt fixes. > Xenomai ran over a 2.6.30 kernel with my own KVM-enabler patch. > > Early instrumentation actually points to the guest exit itself: I added= > markers right before and after the assembly part of vmx_vcpu_run, and > further instrumentation reports that the next host APIC tick should go > off right inside guest mode. But KVM leaves the switching part 500 us > too late in that case - as if guest exit on external IRQs was disabled.= > > Will debug this further, but I'm also curious to hear other user > experiences. > > Jan > > =20 Hi Jan, Did you try to run with latency-tracer enabled? If not, this may pinpoint the source for you. Regards, -Greg --------------enig55B498C56C17C035599A340D Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.11 (Darwin) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkpovV0ACgkQP5K2CMvXmqEmEQCfaio2q20QBumCXQuhzYyK8zng RPMAnifTfYVEiZjwR7GKm6F5K4Q+MfVl =MQsz -----END PGP SIGNATURE----- --------------enig55B498C56C17C035599A340D--