linux-kernel - Re: [PATCH] mm, x86: no zeroing of hugetlbfs pages at boot

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Date:	Thu, 14 Mar 2013 09:51:38 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Cliff Wickman <cpw@....com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
	wli@...omorphy.com
Subject: Re: [PATCH] mm, x86: no zeroing of hugetlbfs pages at boot

On Wed 06-03-13 15:50:20, Cliff Wickman wrote:
[...]
> I propose passing a flag to the early allocator to indicate that no zeroing
> of a page should be done.  The 'no zeroing' flag would have to be passed
> down this code path:
> 
>   hugetlb_hstate_alloc_pages
>     alloc_bootmem_huge_page
>       __alloc_bootmem_node_nopanic NO_ZERO  (nobootmem.c)
>         __alloc_memory_core_early  NO_ZERO
> 	  if (!(flags & NO_ZERO))
>             memset(ptr, 0, size);
> 
> Or this path if CONFIG_NO_BOOTMEM is not set:
> 
>   hugetlb_hstate_alloc_pages
>     alloc_bootmem_huge_page
>       __alloc_bootmem_node_nopanic  NO_ZERO  (bootmem.c)
>         alloc_bootmem_core          NO_ZERO
> 	  if (!(flags & NO_ZERO))
>             memset(region, 0, size);
>         __alloc_bootmem_nopanic     NO_ZERO
>           ___alloc_bootmem_nopanic  NO_ZERO
>             alloc_bootmem_core      NO_ZERO
> 	      if (!(flags & NO_ZERO))
>                 memset(region, 0, size);

Yes, the patch makes sense. I just think it make unnecessary churn.
Can we just add __alloc_bootmem_node_nopanic_nozero and hide the flag
downwards the call chain so that we do not have to touch all
__alloc_bootmem_node_nopanic callers?

Thanks

> Signed-off-by: Cliff Wickman <cpw@....com>
> 
> ---
>  arch/x86/kernel/setup_percpu.c |    4 ++--
>  include/linux/bootmem.h        |   23 ++++++++++++++++-------
>  mm/bootmem.c                   |   12 +++++++-----
>  mm/hugetlb.c                   |    3 ++-
>  mm/nobootmem.c                 |   41 +++++++++++++++++++++++------------------
>  mm/page_cgroup.c               |    2 +-
>  mm/sparse.c                    |    2 +-
>  7 files changed, 52 insertions(+), 35 deletions(-)
> 
[...]
-- 
Michal Hocko
SUSE Labs
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