[v2,5/5] mm: teach platforms not to zero struct pages memory

If we are using deferred struct page initialization feature, most of
"struct page"es are getting initialized after other CPUs are started, and
hence we are benefiting from doing this job in parallel. However, we are
still zeroing all the memory that is allocated for "struct pages" using the
boot CPU.  This patch solves this problem, by deferring zeroing "struct
pages" to only when they are initialized.

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Shannon Nelson <shannon.nelson@oracle.com>
---
 arch/powerpc/mm/init_64.c |    2 +-
 arch/s390/mm/vmem.c       |    2 +-
 arch/sparc/mm/init_64.c   |    2 +-
 arch/x86/mm/init_64.c     |    2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

On Fri, Mar 24, 2017 at 03:19:52PM -0400, Pavel Tatashin wrote:
> If we are using deferred struct page initialization feature, most of
> "struct page"es are getting initialized after other CPUs are started, and
> hence we are benefiting from doing this job in parallel. However, we are
> still zeroing all the memory that is allocated for "struct pages" using the
> boot CPU.  This patch solves this problem, by deferring zeroing "struct
> pages" to only when they are initialized.
> 
> Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
> Reviewed-by: Shannon Nelson <shannon.nelson@oracle.com>
> ---
>  arch/powerpc/mm/init_64.c |    2 +-
>  arch/s390/mm/vmem.c       |    2 +-
>  arch/sparc/mm/init_64.c   |    2 +-
>  arch/x86/mm/init_64.c     |    2 +-
>  4 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
> index eb4c270..24faf2d 100644
> --- a/arch/powerpc/mm/init_64.c
> +++ b/arch/powerpc/mm/init_64.c
> @@ -181,7 +181,7 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
>  		if (vmemmap_populated(start, page_size))
>  			continue;
> 
> -		p = vmemmap_alloc_block(page_size, node, true);
> +		p = vmemmap_alloc_block(page_size, node, VMEMMAP_ZERO);
>  		if (!p)
>  			return -ENOMEM;
> 
> diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
> index 9c75214..ffe9ba1 100644
> --- a/arch/s390/mm/vmem.c
> +++ b/arch/s390/mm/vmem.c
> @@ -252,7 +252,7 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
>  				void *new_page;
> 
>  				new_page = vmemmap_alloc_block(PMD_SIZE, node,
> -							       true);
> +							       VMEMMAP_ZERO);
>  				if (!new_page)
>  					goto out;
>  				pmd_val(*pm_dir) = __pa(new_page) | sgt_prot;

s390 has two call sites that need to be converted, like you did in one of
your previous patches. The same seems to be true for powerpc, unless there
is a reason to not convert them?

Heiko Carstens <heiko.carstens@de.ibm.com> writes:

> On Fri, Mar 24, 2017 at 03:19:52PM -0400, Pavel Tatashin wrote:
>> If we are using deferred struct page initialization feature, most of
>> "struct page"es are getting initialized after other CPUs are started, and
>> hence we are benefiting from doing this job in parallel. However, we are
>> still zeroing all the memory that is allocated for "struct pages" using the
>> boot CPU.  This patch solves this problem, by deferring zeroing "struct
>> pages" to only when they are initialized.
>> 
>> Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
>> Reviewed-by: Shannon Nelson <shannon.nelson@oracle.com>
>> ---
>>  arch/powerpc/mm/init_64.c |    2 +-
>>  arch/s390/mm/vmem.c       |    2 +-
>>  arch/sparc/mm/init_64.c   |    2 +-
>>  arch/x86/mm/init_64.c     |    2 +-
>>  4 files changed, 4 insertions(+), 4 deletions(-)
>> 
>> diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
>> index eb4c270..24faf2d 100644
>> --- a/arch/powerpc/mm/init_64.c
>> +++ b/arch/powerpc/mm/init_64.c
>> @@ -181,7 +181,7 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
>>  		if (vmemmap_populated(start, page_size))
>>  			continue;
>> 
>> -		p = vmemmap_alloc_block(page_size, node, true);
>> +		p = vmemmap_alloc_block(page_size, node, VMEMMAP_ZERO);
>>  		if (!p)
>>  			return -ENOMEM;
>> 
>> diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
>> index 9c75214..ffe9ba1 100644
>> --- a/arch/s390/mm/vmem.c
>> +++ b/arch/s390/mm/vmem.c
>> @@ -252,7 +252,7 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
>>  				void *new_page;
>> 
>>  				new_page = vmemmap_alloc_block(PMD_SIZE, node,
>> -							       true);
>> +							       VMEMMAP_ZERO);
>>  				if (!new_page)
>>  					goto out;
>>  				pmd_val(*pm_dir) = __pa(new_page) | sgt_prot;
>
> s390 has two call sites that need to be converted, like you did in one of
> your previous patches. The same seems to be true for powerpc, unless there
> is a reason to not convert them?
>

vmemmap_list_alloc is not really struct page allocation right ? We are
just allocating memory to be used as vmemmmap_backing. But considering
we are updating all the three elements of the sturct, we can avoid that
memset . But instead of VMEMMAP_ZERO we can just pass false in that case
?

-aneesh