From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gregory Haskins Subject: Re: [PATCH 4/4] Convert irq notifiers lists to RCU locking. Date: Mon, 13 Jul 2009 09:44:41 -0400 Message-ID: <4A5B3A49.1050906@gmail.com> References: <1247400233-24243-1-git-send-email-gleb@redhat.com> <1247400233-24243-5-git-send-email-gleb@redhat.com> <20090713130256.GC10402@redhat.com> <20090713131128.GI28046@redhat.com> <4A5B35FD.9090208@gmail.com> <20090713133234.GN28046@redhat.com> <20090713134058.GG10402@redhat.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig839CE0AE90520DF6419774E6" Cc: Gleb Natapov , avi@redhat.com, "kvm@vger.kernel.org" , paulmck@linux.vnet.ibm.com To: "Michael S. Tsirkin" Return-path: Received: from mail-px0-f185.google.com ([209.85.216.185]:34049 "EHLO mail-px0-f185.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755860AbZGMNot (ORCPT ); Mon, 13 Jul 2009 09:44:49 -0400 Received: by pxi15 with SMTP id 15so560756pxi.33 for ; Mon, 13 Jul 2009 06:44:49 -0700 (PDT) In-Reply-To: <20090713134058.GG10402@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig839CE0AE90520DF6419774E6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Michael S. Tsirkin wrote: > On Mon, Jul 13, 2009 at 04:32:34PM +0300, Gleb Natapov wrote: > =20 >> Yeah I understand that other RCU read section may introduce delays too= =2E >> The question is how big the delay may be. >> =20 > > I recall seeing the number "at least 3 jiffies" somewhere, but that > might have changed since. > =20 I think it is dependent on how you configure your kernel...but that sounds ballpark for one of the worst-case types IIRC. > =20 >> I don't think multiple >> milliseconds delay in device de-assignment is a big issue though. >> =20 > > Right. My point was that since the sync is done under kvm lock, the > guest can easily get blocked trying to get kvm lock meanwhile. > =20 Yeah, that is really the biggest issue here, I agree. The delay in the actual deassignment path is NBD. Kind Regards, -Greg --------------enig839CE0AE90520DF6419774E6 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 iEYEARECAAYFAkpbOkkACgkQP5K2CMvXmqExSACbBmVGykVqUrsu6K3Hg2GjElOj uZEAn37tvPDc/jlOwYnpADo6z2qA+iBD =pD8T -----END PGP SIGNATURE----- --------------enig839CE0AE90520DF6419774E6--