From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <owner-linux-mm@kvack.org>
Received: from mail-wr0-f200.google.com (mail-wr0-f200.google.com [209.85.128.200])
	by kanga.kvack.org (Postfix) with ESMTP id 7DDDD6B02C3
	for <linux-mm@kvack.org>; Thu, 17 Aug 2017 05:00:43 -0400 (EDT)
Received: by mail-wr0-f200.google.com with SMTP id z96so1655160wrb.5
        for <linux-mm@kvack.org>; Thu, 17 Aug 2017 02:00:43 -0700 (PDT)
Received: from mail-wr0-x242.google.com (mail-wr0-x242.google.com. [2a00:1450:400c:c0c::242])
        by mx.google.com with ESMTPS id c30si2763631edd.454.2017.08.17.02.00.41
        for <linux-mm@kvack.org>
        (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128);
        Thu, 17 Aug 2017 02:00:42 -0700 (PDT)
Received: by mail-wr0-x242.google.com with SMTP id p8so1188689wrf.2
        for <linux-mm@kvack.org>; Thu, 17 Aug 2017 02:00:41 -0700 (PDT)
Date: Thu, 17 Aug 2017 11:00:38 +0200
From: Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCHv4 08/14] x86/mm: Make PGDIR_SHIFT and PTRS_PER_P4D
 variable
Message-ID: <20170817090038.lfhmuk7hpuw2zzwo@gmail.com>
References: <20170808125415.78842-1-kirill.shutemov@linux.intel.com>
 <20170808125415.78842-9-kirill.shutemov@linux.intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20170808125415.78842-9-kirill.shutemov@linux.intel.com>
Sender: owner-linux-mm@kvack.org
List-ID: <linux-mm.kvack.org>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>, Andrew Morton <akpm@linux-foundation.org>, x86@kernel.org, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, Andi Kleen <ak@linux.intel.com>, Dave Hansen <dave.hansen@intel.com>, Andy Lutomirski <luto@amacapital.net>, Michal Hocko <mhocko@kernel.org>, linux-mm@kvack.org, linux-kernel@vger.kernel.org


* Kirill A. Shutemov <kirill.shutemov@linux.intel.com> wrote:

> For boot-time switching between 4- and 5-level paging we need to be able
> to fold p4d page table level at runtime. It requires variable
> PGDIR_SHIFT and PTRS_PER_P4D.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> ---
>  arch/x86/boot/compressed/kaslr.c        |  5 +++++
>  arch/x86/include/asm/pgtable_32.h       |  2 ++
>  arch/x86/include/asm/pgtable_32_types.h |  2 ++
>  arch/x86/include/asm/pgtable_64_types.h | 15 +++++++++++++--
>  arch/x86/kernel/head64.c                |  9 ++++++++-
>  arch/x86/mm/dump_pagetables.c           | 12 +++++-------
>  arch/x86/mm/init_64.c                   |  2 +-
>  arch/x86/mm/kasan_init_64.c             |  2 +-
>  arch/x86/platform/efi/efi_64.c          |  4 ++--
>  include/asm-generic/5level-fixup.h      |  1 +
>  include/asm-generic/pgtable-nop4d.h     |  1 +
>  include/linux/kasan.h                   |  2 +-
>  mm/kasan/kasan_init.c                   |  2 +-
>  13 files changed, 43 insertions(+), 16 deletions(-)

So I'm wondering what the code generation effect of this is - what's the 
before/after vmlinux size?

My guess is that the effect should be very small, as these constants are not 
widely used - but I'm only guessing and could be wrong.

Thanks,

	Ingo

--
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: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>