From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: High vm-exit latencies during kvm boot-up/shutdown Date: Tue, 23 Oct 2007 08:38:20 +0200 Message-ID: <471D96DC.7070809@web.de> References: <471D2D8C.1080202@web.de> <10EA09EFD8728347A513008B6B0DA77A02441127@pdsmsx411.ccr.corp.intel.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============2126570947==" Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: "Dong, Eddie" Return-path: In-Reply-To: <10EA09EFD8728347A513008B6B0DA77A02441127-wq7ZOvIWXbNpB2pF5aRoyrfspsVTdybXVpNB7YpNyf8@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --===============2126570947== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig511178EC7BC3435A03A6904A" This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig511178EC7BC3435A03A6904A Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Dong, Eddie wrote: > kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org wrote: >> Hi, >> >> I'm seeing fairly high vm-exit latencies (300-400 us) during and only >> during qemu/kvm startup and shutdown on a Core2 T5500 in 32-bit mode. >> It's most probably while the VM runs inside bios code. During the rest= >> of the time, while some Linux guest is running, the exit latencies are= >> within microseconds, thus perfectly fine for the real-time scenarios >> I have in mind.=20 >=20 > How is this time spent? All in Qemu? Most probably. I have a function tracer installed, and it does not report any kernel function call between the begin of the asm block and its end. > Usually a kernel only VM Exit cost less than 1us. That's what I'm seeing for the rest as well. I have read that certain guest states do not allow preemptions by external interrupts (here it is the timer IRQ), but both GUEST_INTERRUPTIBILITY_INFO and GUEST_ACTIVITY_STATE are 0 on entry, e.g. Is there a way for the guest to trigger a non-preemptible SMM entry, and that without the kernel noticing it? Jan --------------enig511178EC7BC3435A03A6904A Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFHHZbgniDOoMHTA+kRAneFAJ9ezL9uYaHDeZoYRS39rLjYGRB9GACdE8cr umg3/xF6yjfmI88abn+xEZo= =5glx -----END PGP SIGNATURE----- --------------enig511178EC7BC3435A03A6904A-- --===============2126570947== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ --===============2126570947== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ kvm-devel mailing list kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org https://lists.sourceforge.net/lists/listinfo/kvm-devel --===============2126570947==--