From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51693) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dN7wQ-0005J9-HA for qemu-devel@nongnu.org; Mon, 19 Jun 2017 21:26:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dN7wP-0008TB-HM for qemu-devel@nongnu.org; Mon, 19 Jun 2017 21:26:50 -0400 Received: from ozlabs.org ([2401:3900:2:1::2]:53421) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dN7wO-0008Rc-6b for qemu-devel@nongnu.org; Mon, 19 Jun 2017 21:26:49 -0400 Date: Tue, 20 Jun 2017 09:02:58 +0800 From: David Gibson Message-ID: <20170620010258.GK22449@umbus> References: <08ab93cb-4d42-2b8b-71e6-057b9529d0b7@suse.de> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="J2pR2RtFp0tAjF3C" Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] spapr guests warn "System page size 0x2000 is not enabled in page_size_mask (0x11000). Performance may be slow" on SPARC hosts List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Thomas Huth Cc: Alexander Graf , Peter Maydell , QEMU Developers , Alexey Kardashevskiy --J2pR2RtFp0tAjF3C Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jun 19, 2017 at 12:32:48PM +0200, Thomas Huth wrote: > On 19.06.2017 11:39, Alexander Graf wrote: > > On 06/15/2017 03:33 PM, Peter Maydell wrote: > >> I've just noticed that on a SPARC host, some of the PPC guests > >> warn during make check: > >> > >> /ppc64/prom-env/pseries: > >> qemu-system-ppc64: System page size 0x2000 is not enabled in > >> page_size_mask (0x11000). Performance may be slow > >> > >> Is this really a performance problem on a TCG guest? > >> It makes the 'make check' output a bit noisy, but not > >> unbearably so. > >=20 > > From what I can tell this really only affects DDW which should be page > > size agnostic when only using emulated devices. Maybe Alexey thought of > > using VFIO-pci devices in a TCG guest? >=20 > Maybe we could at least silence the warning by checking > qtest_enabled()? So, 1) Yes, we should at least silence the warning. 2) Certainly the mentioned slowdown shouldn't be significant for TCG guests. 3) I _think_ the restriction which causes the slowdown doesn't even exist for TCG, but I haven't 100% convinced myself of this. I've been sick lately, so my brain isn't working all that well. --=20 David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson --J2pR2RtFp0tAjF3C Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBCAAGBQJZSHQ9AAoJEGw4ysog2bOSb6sP/jwlQZH40DXo9XoLHu6KnmZb awrmPn6Tjib69rorSrg0R5xNkwdBpvJtYaQs53AT0XYbw4Eh2MDX7YbuVoIyQDdD Z7lJCwC6arorJRnFh/QlPo5n88l/X0trU+YEZS+yip/+ZkahWco7ec67b3EHJ0Ze zjyO8T0JgnIKsQqgYxxQ/N5enoJ2xHIeqTZXJTg35AqiDXaxsJmVD5KpNBG8A2A2 pDdTIAYacM/IWx0LmNyuFa+dfFc9ELBxQPfXEoO3X31K6QOcrRTy9nzTmD7hsPgE E45JQC1MrdqOyec1fd10lTqvZrOMHjGFKHAMKJFHWYo0Jy0UI6lJ6sTAMHqHqmF4 ZVLlcdelO/i0ZRFHUdeP/JbedKaE+Si+w4Mg/VTdND1WCoTvwccTrkFsW6mH4NJD Td8suIwpuvjfc9L5go9aQCiqCedoFM/XD2gJ9Bs/nNuF+YGIHv5PCijhUl8eEeaS GXS/X+ngxRSdgr6v8Exn6w6ZpHCS6xnNUlJk3qVs56NXOk4jRxk8mU7NKppOdxae mC59Gp7IiwlQf5jwJElN/xis9i+z/3lVarI3JoDO60G8fkf+oeBvW4vRSCOeB+zB KlAHTjG4rWTR9NaP7IO446VtPE7NFZXG5ISXgqSDOT+9HJAiYhuIzNg+yNjpi0p3 sAuSzuU14CEWqIuXTmHL =qzrz -----END PGP SIGNATURE----- --J2pR2RtFp0tAjF3C--