From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47322) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1chBwz-0005i7-Tn for qemu-devel@nongnu.org; Fri, 24 Feb 2017 04:14:06 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1chBww-0002cy-OL for qemu-devel@nongnu.org; Fri, 24 Feb 2017 04:14:05 -0500 Received: from 9.mo6.mail-out.ovh.net ([87.98.171.146]:48005) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1chBww-0002cd-Hh for qemu-devel@nongnu.org; Fri, 24 Feb 2017 04:14:02 -0500 Received: from player761.ha.ovh.net (b9.ovh.net [213.186.33.59]) by mo6.mail-out.ovh.net (Postfix) with ESMTP id 3503FAB40E for ; Fri, 24 Feb 2017 10:14:00 +0100 (CET) Date: Fri, 24 Feb 2017 10:13:50 +0100 From: Greg Kurz Message-ID: <20170224101350.043b97a6@bahia.lan> In-Reply-To: <20170224045531.7026-1-aik@ozlabs.ru> References: <20170224045531.7026-1-aik@ozlabs.ru> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; boundary="Sig_/LPtf+KqfFXu_u5.JUq0NN3v"; protocol="application/pgp-signature" Subject: Re: [Qemu-devel] [Qemu-ppc] [PATCH qemu] sysemu: support up to 1024 vCPUs List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexey Kardashevskiy Cc: qemu-devel@nongnu.org, qemu-ppc@nongnu.org, Greg Kurz , David Gibson --Sig_/LPtf+KqfFXu_u5.JUq0NN3v Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Fri, 24 Feb 2017 15:55:31 +1100 Alexey Kardashevskiy wrote: > From: Greg Kurz >=20 > Some systems can already provide more than 255 hardware threads. >=20 > Bumping the QEMU limit to 1024 seems reasonable: > - it has no visible overhead in top; > - the limit itself has no effect on hot paths. >=20 > Cc: Greg Kurz > Signed-off-by: Alexey Kardashevskiy > --- >=20 > With ulimit -u/-n bumped (nproc and nofile), I was able to boot a guest > with 1024 CPUs, both with threads=3D1 and threads=3D8. >=20 > It takes time though - 3:15 to get to the guest shell but it is probably > expected on 160-threads machine. >=20 I remember something similiar at the time... also I had to give more RAM to the guest to be able to run 1024 CPUs (sth like 6 gigs versus 512 megs for 1 CPU). With the same amount of guest RAM, each extra CPU would cause the memory used by QEMU to grow about 8 megs. > --- > hw/ppc/spapr.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) >=20 > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > index e465d7ac98..46b81a625d 100644 > --- a/hw/ppc/spapr.c > +++ b/hw/ppc/spapr.c > @@ -2712,7 +2712,7 @@ static void spapr_machine_class_init(ObjectClass *o= c, void *data) > mc->init =3D ppc_spapr_init; > mc->reset =3D ppc_spapr_reset; > mc->block_default_type =3D IF_SCSI; > - mc->max_cpus =3D 255; > + mc->max_cpus =3D 1024; > mc->no_parallel =3D 1; > mc->default_boot_order =3D ""; > mc->default_ram_size =3D 512 * M_BYTE; --Sig_/LPtf+KqfFXu_u5.JUq0NN3v Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iEYEARECAAYFAliv+U4ACgkQAvw66wEB28L5jACdFYQn7nsXoYykpcIEHHs5A0o9 y54AniPdQdcUNXtEAabkZFPEabbJ63Tn =pwL6 -----END PGP SIGNATURE----- --Sig_/LPtf+KqfFXu_u5.JUq0NN3v--