From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [RESEND PATCH 3/3 V2] kvm mmu: reduce 50% memory usage Date: Wed, 26 May 2010 13:04:26 +0300 Message-ID: <4BFCF22A.8050804@redhat.com> References: <4BFCE0B7.1090105@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , LKML , kvm@vger.kernel.org To: Lai Jiangshan Return-path: In-Reply-To: <4BFCE0B7.1090105@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 05/26/2010 11:49 AM, Lai Jiangshan wrote: > I think users will enable tdp when their hardwares support ept or npt. > This patch can reduce about 50% kvm mmu memory usage for they. > > This simple patch use the fact that: > > When sp->role.direct is set, sp->gfns does not contain any essential > information, leaf sptes reachable from this sp are for a continuate > guest physical memory range(a linear range). > So sp->gfns[i](if it was set) equals to sp->gfn + i. (PT_PAGE_TABLE_LEVEL) > Obviously, it is not essential information, we can calculate it when need. > > It means we don't need sp->gfns when sp->role.direct=1, > Thus we can save one page usage for every kvm_mmu_page. > > Note: > Access to sp->gfns must be wrapped by kvm_mmu_page_get_gfn() > or kvm_mmu_page_set_gfn(). > It is only exposed in FNAME(sync_page). > > Applied, thanks. -- error compiling committee.c: too many arguments to function