From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH v3 5/5] KVM: Allow host IRQ sharing for passed-through PCI 2.3 devices Date: Wed, 03 Nov 2010 10:18:05 +0100 Message-ID: <4CD128CD.9000705@web.de> References: <628f014fb1efb8e2208db03d13198ba301a3a34c.1288771873.git.jan.kiszka@web.de> <20101103082921.GD6772@redhat.com> <4CD123B8.8080607@web.de> <20101103091045.GH6772@redhat.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig3BEE624E8420568B660CF758" Cc: Avi Kivity , Marcelo Tosatti , kvm , Alex Williamson , Jan Kiszka To: "Michael S. Tsirkin" Return-path: Received: from fmmailgate01.web.de ([217.72.192.221]:46707 "EHLO fmmailgate01.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753685Ab0KCJSM (ORCPT ); Wed, 3 Nov 2010 05:18:12 -0400 In-Reply-To: <20101103091045.GH6772@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig3BEE624E8420568B660CF758 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Am 03.11.2010 10:10, Michael S. Tsirkin wrote: > On Wed, Nov 03, 2010 at 09:56:24AM +0100, Jan Kiszka wrote: >>> Hmm, this does an extra config read on each interrupt (another one is= in >>> pci_2_3_irq_unmask). These reads are pretty expensive... I do realiz= e >>> locking becomes ugly, though. Maybe my idea to avoid set level to 0 >>> was silly? Thoughts? >> >> Well, reading twice is the price to pay here, putting kvm_set_irq unde= r >> spin_lock_irq again is a no-go. From that POV, the previous version wa= s >> probably the cheapest: no extra efforts in the common case, but still >> avoiding reassertion via the host IRQ handler whenever possible. >> >> Jan >> >=20 > Sigh. I guess so. Any chance of a benchmark to let us figure this out? >=20 Will see what I can do. 2.6.37 claims to have improved IRQ load accounting, maybe that helps to measure something useful. Jan --------------enig3BEE624E8420568B660CF758 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.15 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org/ iEYEARECAAYFAkzRKNIACgkQitSsb3rl5xSgFwCffykM1cEst6wG8QLIi3xFTGCY nAsAnjyXIQn00m6hsEZAMatw/9XOPBq4 =aOB6 -----END PGP SIGNATURE----- --------------enig3BEE624E8420568B660CF758--