* + mm-sparse-refine-usemap_size-a-little.patch added to -mm tree
@ 2017-03-10 22:41 akpm
2017-03-16 9:17 ` Michal Hocko
0 siblings, 1 reply; 4+ messages in thread
From: akpm @ 2017-03-10 22:41 UTC (permalink / raw)
To: richard.weiyang, tj, mm-commits
The patch titled
Subject: mm/sparse: refine usemap_size() a little
has been added to the -mm tree. Its filename is
mm-sparse-refine-usemap_size-a-little.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-sparse-refine-usemap_size-a-little.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-sparse-refine-usemap_size-a-little.patch
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------------------------------------------------------
From: Wei Yang <richard.weiyang@gmail.com>
Subject: mm/sparse: refine usemap_size() a little
Current implementation calculates usemap_size in two steps:
* calculate number of bytes to cover these bits
* calculate number of "unsigned long" to cover these bytes
It would be more clear by:
* calculate number of "unsigned long" to cover these bits
* multiple it with sizeof(unsigned long)
This patch refine usemap_size() a little to make it more easy to
understand.
Link: http://lkml.kernel.org/r/20170310043713.96871-1-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/sparse.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff -puN mm/sparse.c~mm-sparse-refine-usemap_size-a-little mm/sparse.c
--- a/mm/sparse.c~mm-sparse-refine-usemap_size-a-little
+++ a/mm/sparse.c
@@ -248,10 +248,7 @@ static int __meminit sparse_init_one_sec
unsigned long usemap_size(void)
{
- unsigned long size_bytes;
- size_bytes = roundup(SECTION_BLOCKFLAGS_BITS, 8) / 8;
- size_bytes = roundup(size_bytes, sizeof(unsigned long));
- return size_bytes;
+ return BITS_TO_LONGS(SECTION_BLOCKFLAGS_BITS) * sizeof(unsigned long);
}
#ifdef CONFIG_MEMORY_HOTPLUG
_
Patches currently in -mm which might be from richard.weiyang@gmail.com are
mm-sparse-refine-usemap_size-a-little.patch
mm-page_alloc-return-0-in-case-this-node-has-no-page-within-the-zone.patch
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: + mm-sparse-refine-usemap_size-a-little.patch added to -mm tree
2017-03-10 22:41 + mm-sparse-refine-usemap_size-a-little.patch added to -mm tree akpm
@ 2017-03-16 9:17 ` Michal Hocko
0 siblings, 0 replies; 4+ messages in thread
From: Michal Hocko @ 2017-03-16 9:17 UTC (permalink / raw)
To: linux-kernel; +Cc: richard.weiyang, tj, mm-commits, Mel Gorman, linux-mm
[CC Mel]
On Fri 10-03-17 14:41:22, Andrew Morton wrote:
> From: Wei Yang <richard.weiyang@gmail.com>
> Subject: mm/sparse: refine usemap_size() a little
>
> Current implementation calculates usemap_size in two steps:
> * calculate number of bytes to cover these bits
> * calculate number of "unsigned long" to cover these bytes
>
> It would be more clear by:
> * calculate number of "unsigned long" to cover these bits
> * multiple it with sizeof(unsigned long)
>
> This patch refine usemap_size() a little to make it more easy to
> understand.
I haven't checked deeply yet but reading through 5c0e3066474b ("Fix
corruption of memmap on IA64 SPARSEMEM when mem_section is not a power
of 2") made me ask whether the case described in the commit message
still applies after this change or whether it has been considered at
all.
> Link: http://lkml.kernel.org/r/20170310043713.96871-1-richard.weiyang@gmail.com
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> Cc: Tejun Heo <tj@kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
>
> mm/sparse.c | 5 +----
> 1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff -puN mm/sparse.c~mm-sparse-refine-usemap_size-a-little mm/sparse.c
> --- a/mm/sparse.c~mm-sparse-refine-usemap_size-a-little
> +++ a/mm/sparse.c
> @@ -248,10 +248,7 @@ static int __meminit sparse_init_one_sec
>
> unsigned long usemap_size(void)
> {
> - unsigned long size_bytes;
> - size_bytes = roundup(SECTION_BLOCKFLAGS_BITS, 8) / 8;
> - size_bytes = roundup(size_bytes, sizeof(unsigned long));
> - return size_bytes;
> + return BITS_TO_LONGS(SECTION_BLOCKFLAGS_BITS) * sizeof(unsigned long);
> }
>
> #ifdef CONFIG_MEMORY_HOTPLUG
> _
>
> Patches currently in -mm which might be from richard.weiyang@gmail.com are
>
> mm-sparse-refine-usemap_size-a-little.patch
> mm-page_alloc-return-0-in-case-this-node-has-no-page-within-the-zone.patch
>
> --
> To unsubscribe from this list: send the line "unsubscribe mm-commits" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: + mm-sparse-refine-usemap_size-a-little.patch added to -mm tree
@ 2017-03-16 9:17 ` Michal Hocko
0 siblings, 0 replies; 4+ messages in thread
From: Michal Hocko @ 2017-03-16 9:17 UTC (permalink / raw)
To: linux-kernel; +Cc: richard.weiyang, tj, mm-commits, Mel Gorman, linux-mm
[CC Mel]
On Fri 10-03-17 14:41:22, Andrew Morton wrote:
> From: Wei Yang <richard.weiyang@gmail.com>
> Subject: mm/sparse: refine usemap_size() a little
>
> Current implementation calculates usemap_size in two steps:
> * calculate number of bytes to cover these bits
> * calculate number of "unsigned long" to cover these bytes
>
> It would be more clear by:
> * calculate number of "unsigned long" to cover these bits
> * multiple it with sizeof(unsigned long)
>
> This patch refine usemap_size() a little to make it more easy to
> understand.
I haven't checked deeply yet but reading through 5c0e3066474b ("Fix
corruption of memmap on IA64 SPARSEMEM when mem_section is not a power
of 2") made me ask whether the case described in the commit message
still applies after this change or whether it has been considered at
all.
> Link: http://lkml.kernel.org/r/20170310043713.96871-1-richard.weiyang@gmail.com
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> Cc: Tejun Heo <tj@kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
>
> mm/sparse.c | 5 +----
> 1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff -puN mm/sparse.c~mm-sparse-refine-usemap_size-a-little mm/sparse.c
> --- a/mm/sparse.c~mm-sparse-refine-usemap_size-a-little
> +++ a/mm/sparse.c
> @@ -248,10 +248,7 @@ static int __meminit sparse_init_one_sec
>
> unsigned long usemap_size(void)
> {
> - unsigned long size_bytes;
> - size_bytes = roundup(SECTION_BLOCKFLAGS_BITS, 8) / 8;
> - size_bytes = roundup(size_bytes, sizeof(unsigned long));
> - return size_bytes;
> + return BITS_TO_LONGS(SECTION_BLOCKFLAGS_BITS) * sizeof(unsigned long);
> }
>
> #ifdef CONFIG_MEMORY_HOTPLUG
> _
>
> Patches currently in -mm which might be from richard.weiyang@gmail.com are
>
> mm-sparse-refine-usemap_size-a-little.patch
> mm-page_alloc-return-0-in-case-this-node-has-no-page-within-the-zone.patch
>
> --
> To unsubscribe from this list: send the line "unsubscribe mm-commits" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Michal Hocko
SUSE Labs
--
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: + mm-sparse-refine-usemap_size-a-little.patch added to -mm tree
2017-03-16 9:17 ` Michal Hocko
(?)
@ 2017-03-17 1:47 ` Wei Yang
-1 siblings, 0 replies; 4+ messages in thread
From: Wei Yang @ 2017-03-17 1:47 UTC (permalink / raw)
To: Michal Hocko
Cc: linux-kernel, richard.weiyang, tj, mm-commits, Mel Gorman, linux-mm
[-- Attachment #1: Type: text/plain, Size: 1702 bytes --]
On Thu, Mar 16, 2017 at 10:17:18AM +0100, Michal Hocko wrote:
>[CC Mel]
>
>On Fri 10-03-17 14:41:22, Andrew Morton wrote:
>> From: Wei Yang <richard.weiyang@gmail.com>
>> Subject: mm/sparse: refine usemap_size() a little
>>
>> Current implementation calculates usemap_size in two steps:
>> * calculate number of bytes to cover these bits
>> * calculate number of "unsigned long" to cover these bytes
>>
>> It would be more clear by:
>> * calculate number of "unsigned long" to cover these bits
>> * multiple it with sizeof(unsigned long)
>>
>> This patch refine usemap_size() a little to make it more easy to
>> understand.
>
>I haven't checked deeply yet but reading through 5c0e3066474b ("Fix
>corruption of memmap on IA64 SPARSEMEM when mem_section is not a power
>of 2") made me ask whether the case described in the commit message
>still applies after this change or whether it has been considered at
>all.
>
Hi, Michal
Thanks for your comment.
By looking into the commit 5c0e3066474b, I think it does two things:
1. Recalculate the SECTION_BLOCKFLAGS_BITS
2. Move pageblock_flags out mem_section to make the structure power of 2 in
size.
When we look at the original data structure, pageblock_flags originally is
defined as a bitmap:
DECLARE_BITMAP(pageblock_flags, SECTION_BLOCKFLAGS_BITS);
Which in turn is:
#define DECLARE_BITMAP(pageblock_flags,SECTION_BLOCKFLAGS_BITS) \
unsigned long pageblock_flags[BITS_TO_LONGS(SECTION_BLOCKFLAGS_BITS)]
My patch is using BITS_TO_LONGS() to simplify the code and obviously has the
same effect.
Does this resolve your concern?
--
Wei Yang
Help you, Help me
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^ permalink raw reply [flat|nested] 4+ messages in thread
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2017-03-10 22:41 + mm-sparse-refine-usemap_size-a-little.patch added to -mm tree akpm
2017-03-16 9:17 ` Michal Hocko
2017-03-16 9:17 ` Michal Hocko
2017-03-17 1:47 ` Wei Yang
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