On Tue 26-06-12 14:07:35, 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?
> >
>
> Yeah, I do agree it won't do much optimization here. However, I'm wandering
> if I can remove the whole peice of code doing memset(setion, 0, array_size)
> since it seems that alloc_bootmem_node() also clears the allocated memory
> chunk :-)
Yes, alloc_bootem_node clears the memory (strange, I thought it doesn't
do that), so the memset is really not necessary after s/kmalloc/kzalloc/.
>
> Please correct me if I'm wrong about alloc_bootmem_node() :-)
>
> Thanks,
> Gavin
>
> >>
> >> Signed-off-by: Gavin Shan <shangw@xxxxxxxxxxxxxxxxxx>
> >> ---
> >> 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
> >>
> >> --
> >> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> >> the body to majordomo@xxxxxxxxx. For more info on Linux MM,
> >> see: http://www.linux-mm.org/ .
> >> Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
> >
> >--
> >Michal Hocko
> >SUSE Labs
> >SUSE LINUX s.r.o.
> >Lihovarska 1060/12
> >190 00 Praha 9
> >Czech Republic
> >
> >--
> >To unsubscribe, send a message with 'unsubscribe linux-mm' in
> >the body to majordomo@xxxxxxxxx. For more info on Linux MM,
> >see: http://www.linux-mm.org/ .
> >Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
> >
>
--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic
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