Re: [PATCH 2/5] mm/sparse: optimize sparse_index_alloc

[Michal Hocko <mhocko@suse.cz>]

On Sat 23-06-12 23:52:53, Gavin Shan wrote:
> With CONFIG_SPARSEMEM_EXTREME, the two level of memory section
> descriptors are allocated from slab or bootmem. When allocating
> from slab, let slab allocator to clear the memory chunk. However,
> the memory chunk from bootmem allocator, we have to clear that
> explicitly.

I am sorry but I do not see how this optimize the current code. What is
the difference between slab doing memset and doing it explicitly for all
cases?

> 
> Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>
> ---
>  mm/sparse.c |   12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/sparse.c b/mm/sparse.c
> index afd0998..ce50c8b 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -74,14 +74,14 @@ static struct mem_section noinline __init_refok *sparse_index_alloc(int nid)
>  
>  	if (slab_is_available()) {
>  		if (node_state(nid, N_HIGH_MEMORY))
> -			section = kmalloc_node(array_size, GFP_KERNEL, nid);
> +			section = kzalloc_node(array_size, GFP_KERNEL, nid);
>  		else
> -			section = kmalloc(array_size, GFP_KERNEL);
> -	} else
> +			section = kzalloc(array_size, GFP_KERNEL);
> +	} else {
>  		section = alloc_bootmem_node(NODE_DATA(nid), array_size);
> -
> -	if (section)
> -		memset(section, 0, array_size);
> +		if (section)
> +			memset(section, 0, array_size);
> +	}
>  
>  	return section;
>  }
> -- 
> 1.7.9.5
> 
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-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic

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