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Groups > linux.kernel > #1473005 > unrolled thread
| Started by | Anshuman Khandual <khandual@linux.vnet.ibm.com> |
|---|---|
| First post | 2016-08-31 05:30 +0200 |
| Last post | 2016-09-02 06:30 +0200 |
| Articles | 3 — 2 participants |
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[PATCH 1/2] mm: Move definition of 'zone_names' array into mmzone.h Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2016-08-31 05:30 +0200
Re: [PATCH 1/2] mm: Move definition of 'zone_names' array into mmzone.h Andrew Morton <akpm@linux-foundation.org> - 2016-08-31 23:20 +0200
Re: [PATCH 1/2] mm: Move definition of 'zone_names' array into mmzone.h Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2016-09-02 06:30 +0200
| From | Anshuman Khandual <khandual@linux.vnet.ibm.com> |
|---|---|
| Date | 2016-08-31 05:30 +0200 |
| Subject | [PATCH 1/2] mm: Move definition of 'zone_names' array into mmzone.h |
| Message-ID | <sc4nZ-5qM-7@gated-at.bofh.it> |
zone_names[] is used to identify any zone given it's index which
can be used in many other places. So moving the definition into
include/linux/mmzone.h for broader access.
Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
---
include/linux/mmzone.h | 17 +++++++++++++++++
mm/page_alloc.c | 17 -----------------
2 files changed, 17 insertions(+), 17 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index d572b78..01ca3f4 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -341,6 +341,23 @@ enum zone_type {
};
+static char * const zone_names[__MAX_NR_ZONES] = {
+#ifdef CONFIG_ZONE_DMA
+ "DMA",
+#endif
+#ifdef CONFIG_ZONE_DMA32
+ "DMA32",
+#endif
+ "Normal",
+#ifdef CONFIG_HIGHMEM
+ "HighMem",
+#endif
+ "Movable",
+#ifdef CONFIG_ZONE_DEVICE
+ "Device",
+#endif
+};
+
#ifndef __GENERATING_BOUNDS_H
struct zone {
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3fbe73a..8e2261c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -207,23 +207,6 @@ int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1] = {
EXPORT_SYMBOL(totalram_pages);
-static char * const zone_names[MAX_NR_ZONES] = {
-#ifdef CONFIG_ZONE_DMA
- "DMA",
-#endif
-#ifdef CONFIG_ZONE_DMA32
- "DMA32",
-#endif
- "Normal",
-#ifdef CONFIG_HIGHMEM
- "HighMem",
-#endif
- "Movable",
-#ifdef CONFIG_ZONE_DEVICE
- "Device",
-#endif
-};
-
char * const migratetype_names[MIGRATE_TYPES] = {
"Unmovable",
"Movable",
--
1.9.3
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| From | Andrew Morton <akpm@linux-foundation.org> |
|---|---|
| Date | 2016-08-31 23:20 +0200 |
| Subject | Re: [PATCH 1/2] mm: Move definition of 'zone_names' array into mmzone.h |
| Message-ID | <scl5n-7Av-3@gated-at.bofh.it> |
| In reply to | #1473005 |
On Wed, 31 Aug 2016 08:55:49 +0530 Anshuman Khandual <khandual@linux.vnet.ibm.com> wrote:
> zone_names[] is used to identify any zone given it's index which
> can be used in many other places. So moving the definition into
> include/linux/mmzone.h for broader access.
>
> ...
>
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -341,6 +341,23 @@ enum zone_type {
>
> };
>
> +static char * const zone_names[__MAX_NR_ZONES] = {
> +#ifdef CONFIG_ZONE_DMA
> + "DMA",
> +#endif
> +#ifdef CONFIG_ZONE_DMA32
> + "DMA32",
> +#endif
> + "Normal",
> +#ifdef CONFIG_HIGHMEM
> + "HighMem",
> +#endif
> + "Movable",
> +#ifdef CONFIG_ZONE_DEVICE
> + "Device",
> +#endif
> +};
> +
> #ifndef __GENERATING_BOUNDS_H
>
> struct zone {
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 3fbe73a..8e2261c 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -207,23 +207,6 @@ int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1] = {
>
> EXPORT_SYMBOL(totalram_pages);
>
> -static char * const zone_names[MAX_NR_ZONES] = {
> -#ifdef CONFIG_ZONE_DMA
> - "DMA",
> -#endif
> -#ifdef CONFIG_ZONE_DMA32
> - "DMA32",
> -#endif
> - "Normal",
> -#ifdef CONFIG_HIGHMEM
> - "HighMem",
> -#endif
> - "Movable",
> -#ifdef CONFIG_ZONE_DEVICE
> - "Device",
> -#endif
> -};
> -
> char * const migratetype_names[MIGRATE_TYPES] = {
> "Unmovable",
> "Movable",
This is worrisome. On some (ancient) compilers, this will produce a
copy of that array into each compilation unit which includes mmzone.h.
On smarter compilers, it will produce a copy of the array in each
compilation unit which *uses* zone_names[].
On even smarter compilers (and linkers!), only one copy of zone_names[]
will exist in vmlinux.
I don't know if gcc is an "even smarter compiler" and I didn't check,
and I didn't check which gcc versions are even smarter. I'd rather not
have to ;) It is risky.
So, let's just make it non-static and add a declaration into mmzone.h,
please.
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| From | Anshuman Khandual <khandual@linux.vnet.ibm.com> |
|---|---|
| Date | 2016-09-02 06:30 +0200 |
| Message-ID | <scOh4-33O-15@gated-at.bofh.it> |
| In reply to | #1473886 |
On 09/01/2016 02:40 AM, Andrew Morton wrote:
> On Wed, 31 Aug 2016 08:55:49 +0530 Anshuman Khandual <khandual@linux.vnet.ibm.com> wrote:
>
>> zone_names[] is used to identify any zone given it's index which
>> can be used in many other places. So moving the definition into
>> include/linux/mmzone.h for broader access.
>>
>> ...
>>
>> --- a/include/linux/mmzone.h
>> +++ b/include/linux/mmzone.h
>> @@ -341,6 +341,23 @@ enum zone_type {
>>
>> };
>>
>> +static char * const zone_names[__MAX_NR_ZONES] = {
>> +#ifdef CONFIG_ZONE_DMA
>> + "DMA",
>> +#endif
>> +#ifdef CONFIG_ZONE_DMA32
>> + "DMA32",
>> +#endif
>> + "Normal",
>> +#ifdef CONFIG_HIGHMEM
>> + "HighMem",
>> +#endif
>> + "Movable",
>> +#ifdef CONFIG_ZONE_DEVICE
>> + "Device",
>> +#endif
>> +};
>> +
>> #ifndef __GENERATING_BOUNDS_H
>>
>> struct zone {
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 3fbe73a..8e2261c 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -207,23 +207,6 @@ int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1] = {
>>
>> EXPORT_SYMBOL(totalram_pages);
>>
>> -static char * const zone_names[MAX_NR_ZONES] = {
>> -#ifdef CONFIG_ZONE_DMA
>> - "DMA",
>> -#endif
>> -#ifdef CONFIG_ZONE_DMA32
>> - "DMA32",
>> -#endif
>> - "Normal",
>> -#ifdef CONFIG_HIGHMEM
>> - "HighMem",
>> -#endif
>> - "Movable",
>> -#ifdef CONFIG_ZONE_DEVICE
>> - "Device",
>> -#endif
>> -};
>> -
>> char * const migratetype_names[MIGRATE_TYPES] = {
>> "Unmovable",
>> "Movable",
>
> This is worrisome. On some (ancient) compilers, this will produce a
> copy of that array into each compilation unit which includes mmzone.h.
>
> On smarter compilers, it will produce a copy of the array in each
> compilation unit which *uses* zone_names[].
>
> On even smarter compilers (and linkers!), only one copy of zone_names[]
> will exist in vmlinux.
>
> I don't know if gcc is an "even smarter compiler" and I didn't check,
> and I didn't check which gcc versions are even smarter. I'd rather not
> have to ;) It is risky.
>
> So, let's just make it non-static and add a declaration into mmzone.h,
> please.
>
I understand your concern, will change it.
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