linux-kernel - Re: [PATCH 0/3] Virtual huge zero page

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Message-ID: <20120929143006.GC4110@tassilo.jf.intel.com>
Date:	Sat, 29 Sep 2012 07:30:06 -0700
From:	Andi Kleen <ak@...ux.intel.com>
To:	Andrea Arcangeli <aarcange@...hat.com>
Cc:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Arnd Bergmann <arnd@...db.de>, Ingo Molnar <mingo@...nel.org>,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH 0/3] Virtual huge zero page

On Sat, Sep 29, 2012 at 03:48:11PM +0200, Andrea Arcangeli wrote:
> On Sat, Sep 29, 2012 at 02:37:18AM +0300, Kirill A. Shutemov wrote:
> > Cons:
> >  - increases TLB pressure;
> 
> I generally don't like using 4k tlb entries ever. This only has the

>From theory I would also prefer the 2MB huge page.

But some numbers comparing between the two alternatives are definitely
interesting.  Numbers are often better than theory.

> There would be a small cache benefit here... but even then some first
> level caches are virtually indexed IIRC (always physically tagged to

Modern x86 doesn't have virtually indexed caches.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only
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