From: Michal Hocko <mhocko@suse.cz>
To: Gavin Shan <shangw@linux.vnet.ibm.com>
Cc: linux-mm@kvack.org, rientjes@google.com, hannes@cmpxchg.org,
akpm@linux-foundation.org
Subject: Re: [PATCH 1/5] mm/sparse: check size of struct mm_section
Date: Tue, 26 Jun 2012 09:39:13 +0200 [thread overview]
Message-ID: <20120626073913.GC6713@tiehlicka.suse.cz> (raw)
In-Reply-To: <20120625163522.GA5476@shangw>
On Tue 26-06-12 00:35:22, Gavin Shan wrote:
[...]
> >> In order to fully utilize the memory chunk allocated from bootmem
> >> allocator, it'd better to assure memory sector descriptor won't run
> >> across the boundary (PAGE_SIZE).
OK, I misread this part of the changelog changelog.
> >
> >Why? The memory is continuous, right?
>
> Yes, the memory is conginous and the capacity of specific entry
> in mem_section[NR_SECTION_ROOTS] has been defined as follows:
>
>
> #define SECTIONS_PER_ROOT (PAGE_SIZE / sizeof (struct mem_section))
>
> Also, the memory is prone to be allocated from bootmem by function
> alloc_bootmem_node(), which has PAGE_SIZE alignment. So I think it's
> reasonable to introduce the extra check here from my personal view :-)
No it is not necessary because we will never cross the page boundary
because (SECTIONS_PER_ROOT uses an int division)
--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic
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next prev parent reply other threads:[~2012-06-26 7:39 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-23 15:52 [PATCH 1/5] mm/sparse: check size of struct mm_section Gavin Shan
2012-06-23 15:52 ` [PATCH 2/5] mm/sparse: optimize sparse_index_alloc Gavin Shan
2012-06-25 15:30 ` Michal Hocko
2012-06-26 6:07 ` Gavin Shan
2012-06-26 7:04 ` Michal Hocko
2012-06-26 7:13 ` Gavin Shan
2012-06-23 15:52 ` [PATCH 3/5] mm/sparse: fix possible memory leak Gavin Shan
2012-06-25 15:48 ` Michal Hocko
2012-06-26 6:11 ` Gavin Shan
2012-06-26 7:14 ` Michal Hocko
2012-06-26 7:17 ` Gavin Shan
2012-06-23 15:52 ` [PATCH 4/5] mm/sparse: more check on mem_section number Gavin Shan
2012-06-26 16:15 ` Dave Hansen
2012-06-27 0:29 ` Gavin Shan
2012-06-23 15:52 ` [PATCH 5/5] mm/sparse: return 0 if root mem_section exists Gavin Shan
2012-06-24 19:18 ` KOSAKI Motohiro
2012-06-25 1:09 ` Gavin Shan
2012-06-25 15:39 ` Michal Hocko
2012-06-25 16:03 ` [PATCH 1/5] mm/sparse: check size of struct mm_section Michal Hocko
2012-06-25 16:35 ` Gavin Shan
2012-06-26 7:39 ` Michal Hocko [this message]
2012-06-26 7:48 ` Gavin Shan
2012-06-26 8:06 ` Michal Hocko
2012-06-26 8:24 ` Gavin Shan
2012-06-26 17:57 ` Michal Hocko
2012-06-27 3:01 ` Gavin Shan
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