From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52676) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1f67e8-0005lu-FS for qemu-devel@nongnu.org; Wed, 11 Apr 2018 00:46:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1f67e4-0006Qq-9n for qemu-devel@nongnu.org; Wed, 11 Apr 2018 00:46:12 -0400 Date: Wed, 11 Apr 2018 14:21:43 +1000 From: David Gibson Message-ID: <20180411042143.GB2124@umbus.fritz.box> References: <20180409062538.1095-1-bharata@linux.vnet.ibm.com> <20180410030245.GF3361@umbus.fritz.box> <20180410041521.GA14855@in.ibm.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="8P1HSweYDcXXzwPJ" Content-Disposition: inline In-Reply-To: <20180410041521.GA14855@in.ibm.com> Subject: Re: [Qemu-devel] [RFC PATCH v2] spapr: Support ibm, dynamic-memory-v2 property List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Bharata B Rao , y@umbus.fritz.box Cc: qemu-devel@nongnu.org, qemu-ppc@nongnu.org, nfont@linux.vnet.ibm.com, mwb@linux.vnet.ibm.com, imammedo@redhat.com --8P1HSweYDcXXzwPJ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Apr 10, 2018 at 09:45:21AM +0530, Bharata B Rao wrote: > On Tue, Apr 10, 2018 at 01:02:45PM +1000, David Gibson wrote: > > On Mon, Apr 09, 2018 at 11:55:38AM +0530, Bharata B Rao wrote: > > > The new property ibm,dynamic-memory-v2 allows memory to be represented > > > in a more compact manner in device tree. > >=20 > > I still need to look at this in more detail, but to start with: > > what's the rationale for this new format? > >=20 > > It's more compact, but why do we care? The embedded people always > > whinge about the size of the deivce tree, but I didn't think that was > > really a concern with PAPR. >=20 > Here's a real example of how this has affected us earlier: >=20 > SLOF's CAS FDT buffer size was initially 32K, was changed to 64k to > support 1TB guest memory and again changed to 2MB to support 16TB guest > memory. Ah.. I hadn't thought of the CAS buffer, that's a legitimate concern. > With ibm,dynamic-memory-v2 we are less likely to hit such scenarios. >=20 > Also, theoretically it should be more efficient in the guest kernel > to handle LMB-sets than individual LMBs. >=20 > We aren't there yet, but I believe grouping of LMBs should eventually > help us do memory hotplug at set (or DIMM) granularity than at individual > LMB granularity (Again theoretical possibility) Ok, sounds like it might be useful. --=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 --8P1HSweYDcXXzwPJ Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEdfRlhq5hpmzETofcbDjKyiDZs5IFAlrNjVcACgkQbDjKyiDZ s5KrPw//Y0rB54al42Zxd+MLlY9wB0Fms6WrUVZZ4qP88dq5R7lTyXmxYFvvsmfx PqXJy+AZ3i+YCpzwG45sjkFzNb5236Uw9bktzKsWoN6dApDIh9S1r2xJR3td1F7X XnIkPt2laXAq30LwaU1NzWyeM8ax+3mB0e5YWLlvO7DVuwVpT3kpNK9Duuda0h+j k+lvmslxNNNVQWQW4liRPuqlcfiUoMw2EK/Q5jAL+VtOtMSZdtTJwe07EYJpp86w txuJsNp5YLdDUsIhmNy9Kgw+wqOp0xEBhcXbmlrM5fz7AZ4D/Zbj13gzF/7btZPD FTsuqfNnoVmMO1ufm13qNxEwGUpMwbyEp9kZVAAJpeZ/pGyuo7rgxJlcB+gx/ia3 jtdHBtphjCa8p/RvXk/zAeu6B1FiH48bzJvkbZuqjNtxAC9BoQSc+DrP3IlM5Jwq QLPNl9nH1sjlXq3GmXFe7YSmxpNrVWJgLi8W3SxepuJ2l7dbMRV9WYjiKE96VsnE fW7fZU+Za0qBHUVBneoLul9wMUR45gqFSfyPfx/rrmWgcOZArA4fIBVhTPyLiCiq qyzxCGFzMz1CypMNfjCO0aTuuNZqGZWnS777TfhpyWahSseQqGdTvqA4BYNNYudD NchnrOVVoh9uG7zGzkD6pVwyrI+A54YI8OfVWMg/AgUXryef0kc= =Qd8I -----END PGP SIGNATURE----- --8P1HSweYDcXXzwPJ--