linux-kernel - Re: [RESEND PATCH 3/3 V2] kvm mmu: reduce 50% memory usage

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Date:	Wed, 26 May 2010 13:04:26 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Lai Jiangshan <laijs@...fujitsu.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, kvm@...r.kernel.org
Subject: Re: [RESEND PATCH 3/3 V2] kvm mmu: reduce 50% memory usage

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

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