From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: assign-dev: Purpose of interrupt_work Date: Mon, 12 Oct 2009 11:04:23 +0200 Message-ID: <4AD2F117.7000403@web.de> References: <4AD2D4B6.7030203@web.de> <20091012071310.GT16702@redhat.com> <4AD2DA57.6030006@web.de> <20091012074513.GV16702@redhat.com> <4AD2DFE2.4050406@web.de> <20091012075715.GW16702@redhat.com> <4AD2E5F8.4070107@web.de> <20091012083913.GX16702@redhat.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigDD812B7E4FBB787C3C6B3F27" Cc: Avi Kivity , kvm-devel To: Gleb Natapov Return-path: Received: from fmmailgate03.web.de ([217.72.192.234]:43344 "EHLO fmmailgate03.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755260AbZJLJIo (ORCPT ); Mon, 12 Oct 2009 05:08:44 -0400 In-Reply-To: <20091012083913.GX16702@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigDD812B7E4FBB787C3C6B3F27 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Gleb Natapov wrote: > On Mon, Oct 12, 2009 at 10:16:56AM +0200, Jan Kiszka wrote: >>>>> Apic is lockless. For ioapic/pic I used spinlocks initially, but Av= i >>>>> prefers mutexes. Theoretically it is possible to make them lockless= , >>>>> but code will be complex and eventually more slow, since more then = two >>>>> atomic operation will be used on irq injection path. >>>> Well, lockless is another thing. >>>> >>>> But also converting to spinlocks would indeed add some overhead: >>>> irqsave/restore. But I wonder if this isn't worth it, at least when >>>> looking at the (supposed to be fast) device passthrough scenario whi= ch >>>> would be simpler and faster. >>>> >>> Avi's point in favor of mutex is: they are as fast as spinlocks when >>> congested and allows preemption when held. >> ...but require scheduler activity in case of dev-passthrough, which is= >> surely playing in a different league. >> > I'd rather remove dev-passthrough completely than continue adding hack = upon hack > upon hack to make is some times kinda sorta work :) Hmm, is this code not needed for the VT-d & Co. case? Or what is the alternative? Jan --------------enigDD812B7E4FBB787C3C6B3F27 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org iEYEARECAAYFAkrS8RcACgkQitSsb3rl5xSVpQCcCnn3/ZX02dhZk8fr40c+Le4K ABEAn3RTJhInkiHDiD0KoCTKecn4R+fp =mP3W -----END PGP SIGNATURE----- --------------enigDD812B7E4FBB787C3C6B3F27--