From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id AC0226B0069 for ; Thu, 15 Dec 2016 20:38:07 -0500 (EST) Received: by mail-pf0-f198.google.com with SMTP id c4so100018244pfb.7 for ; Thu, 15 Dec 2016 17:38:07 -0800 (PST) Received: from mga09.intel.com (mga09.intel.com. [134.134.136.24]) by mx.google.com with ESMTPS id a23si4919687pfe.35.2016.12.15.17.38.06 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 15 Dec 2016 17:38:06 -0800 (PST) From: "Li, Liang Z" Subject: RE: [Qemu-devel] [PATCH kernel v5 0/5] Extend virtio-balloon for fast (de)inflating & fast live migration Date: Fri, 16 Dec 2016 01:38:01 +0000 Message-ID: References: <1480495397-23225-1-git-send-email-liang.z.li@intel.com> <0b18c636-ee67-cbb4-1ba3-81a06150db76@redhat.com> <0b83db29-ebad-2a70-8d61-756d33e33a48@intel.com> <2171e091-46ee-decd-7348-772555d3a5e3@redhat.com> <20161207183817.GE28786@redhat.com> <20161207202824.GH28786@redhat.com> <060287c7-d1af-45d5-70ea-ad35d4bbeb84@intel.com> <01886693-c73e-3696-860b-086417d695e1@intel.com> In-Reply-To: Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: "Hansen, Dave" , Andrea Arcangeli Cc: David Hildenbrand , "kvm@vger.kernel.org" , "mhocko@suse.com" , "mst@redhat.com" , "linux-kernel@vger.kernel.org" , "qemu-devel@nongnu.org" , "linux-mm@kvack.org" , "dgilbert@redhat.com" , "pbonzini@redhat.com" , "akpm@linux-foundation.org" , "virtualization@lists.linux-foundation.org" , "kirill.shutemov@linux.intel.com" > On 12/15/2016 04:48 PM, Li, Liang Z wrote: > >>> It seems we leave too many bit for the pfn, and the bits leave for > >>> length is not enough, How about keep 45 bits for the pfn and 19 bits > >>> for length, 45 bits for pfn can cover 57 bits physical address, that > >>> should be > >> enough in the near feature. > >>> What's your opinion? > >> I still think 'order' makes a lot of sense. But, as you say, 57 bits > >> is enough for > >> x86 for a while. Other architectures.... who knows? >=20 > Thinking about this some more... There are really only two cases that > matter: 4k pages and "much bigger" ones. >=20 > Squeezing each 4k page into 8 bytes of metadata helps guarantee that this > scheme won't regress over the old scheme in any cases. For bigger ranges= , 8 > vs 16 bytes means *nothing*. And 16 bytes will be as good or better than > the old scheme for everything which is >4k. >=20 > How about this: > * 52 bits of 'pfn', 5 bits of 'order', 7 bits of 'length' > * One special 'length' value to mean "actual length in next 8 bytes" >=20 > That should be pretty simple to produce and decode. We have two record > sizes, but I think it is manageable. It works, Now that we intend to use another 8 bytes for length Why not: Use 52 bits for 'pfn', 12 bits for 'length', when the 12 bits is not long e= nough for the 'length' Set the 'length' to a special value to indicate the "actual length in next = 8 bytes". That will be much more simple. Right? Liang -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org