When section mappings are enabled, we allocate vmemmap pages from physically
continuous memory of size PMD_SIZE using vmemmap_alloc_block_buf(). Section
mappings are good to reduce TLB pressure. But when system is highly fragmented
and memory blocks are being hot-added at runtime, its possible that such
physically continuous memory allocations can fail. Rather than failing the
memory hot-add procedure, add a fallback option to allocate vmemmap pages from
discontinuous pages using vmemmap_populate_basepages().
Signed-off-by: Sudarshan Rajagopalan <[email protected]>
Reviewed-by: Gavin Shan <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Anshuman Khandual <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Logan Gunthorpe <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Steven Price <[email protected]>
---
arch/arm64/mm/mmu.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 75df62fea1b6..44486fd0e883 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1121,8 +1121,11 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
void *p = NULL;
p = vmemmap_alloc_block_buf(PMD_SIZE, node, altmap);
- if (!p)
- return -ENOMEM;
+ if (!p) {
+ if (vmemmap_populate_basepages(addr, next, node, altmap))
+ return -ENOMEM;
+ continue;
+ }
pmd_set_huge(pmdp, __pa(p), __pgprot(PROT_SECT_NORMAL));
} else
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
On 10/13/2020 04:35 AM, Sudarshan Rajagopalan wrote:
> When section mappings are enabled, we allocate vmemmap pages from physically
> continuous memory of size PMD_SIZE using vmemmap_alloc_block_buf(). Section
> mappings are good to reduce TLB pressure. But when system is highly fragmented
> and memory blocks are being hot-added at runtime, its possible that such
> physically continuous memory allocations can fail. Rather than failing the
> memory hot-add procedure, add a fallback option to allocate vmemmap pages from
> discontinuous pages using vmemmap_populate_basepages().
There is a checkpatch warning here, which could be fixed while merging ?
WARNING: Possible unwrapped commit description (prefer a maximum 75 chars per line)
#7:
When section mappings are enabled, we allocate vmemmap pages from physically
total: 0 errors, 1 warnings, 13 lines checked
>
> Signed-off-by: Sudarshan Rajagopalan <[email protected]>
> Reviewed-by: Gavin Shan <[email protected]>
> Cc: Catalin Marinas <[email protected]>
> Cc: Will Deacon <[email protected]>
> Cc: Anshuman Khandual <[email protected]>
> Cc: Mark Rutland <[email protected]>
> Cc: Logan Gunthorpe <[email protected]>
> Cc: David Hildenbrand <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: Steven Price <[email protected]>
Nonetheless, this looks fine. Did not see any particular problem
while creating an experimental vmemmap with interleaving section
and base page mapping.
Reviewed-by: Anshuman Khandual <[email protected]>
> ---
> arch/arm64/mm/mmu.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 75df62fea1b6..44486fd0e883 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -1121,8 +1121,11 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> void *p = NULL;
>
> p = vmemmap_alloc_block_buf(PMD_SIZE, node, altmap);
> - if (!p)
> - return -ENOMEM;
> + if (!p) {
> + if (vmemmap_populate_basepages(addr, next, node, altmap))
> + return -ENOMEM;
> + continue;
> + }
>
> pmd_set_huge(pmdp, __pa(p), __pgprot(PROT_SECT_NORMAL));
> } else
>
On 2020-10-13 04:38, Anshuman Khandual wrote:
> On 10/13/2020 04:35 AM, Sudarshan Rajagopalan wrote:
>> When section mappings are enabled, we allocate vmemmap pages from
>> physically
>> continuous memory of size PMD_SIZE using vmemmap_alloc_block_buf().
>> Section
>> mappings are good to reduce TLB pressure. But when system is highly
>> fragmented
>> and memory blocks are being hot-added at runtime, its possible that
>> such
>> physically continuous memory allocations can fail. Rather than failing
>> the
>> memory hot-add procedure, add a fallback option to allocate vmemmap
>> pages from
>> discontinuous pages using vmemmap_populate_basepages().
>
> There is a checkpatch warning here, which could be fixed while merging
> ?
>
> WARNING: Possible unwrapped commit description (prefer a maximum 75
> chars per line)
> #7:
> When section mappings are enabled, we allocate vmemmap pages from
> physically
>
> total: 0 errors, 1 warnings, 13 lines checked
>
Thanks Anshuman for the review. I sent out an updated patch fixing the
checkpatch warning.
>>
>> Signed-off-by: Sudarshan Rajagopalan <[email protected]>
>> Reviewed-by: Gavin Shan <[email protected]>
>> Cc: Catalin Marinas <[email protected]>
>> Cc: Will Deacon <[email protected]>
>> Cc: Anshuman Khandual <[email protected]>
>> Cc: Mark Rutland <[email protected]>
>> Cc: Logan Gunthorpe <[email protected]>
>> Cc: David Hildenbrand <[email protected]>
>> Cc: Andrew Morton <[email protected]>
>> Cc: Steven Price <[email protected]>
>
> Nonetheless, this looks fine. Did not see any particular problem
> while creating an experimental vmemmap with interleaving section
> and base page mapping.
>
> Reviewed-by: Anshuman Khandual <[email protected]>
>
>> ---
>> arch/arm64/mm/mmu.c | 7 +++++--
>> 1 file changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index 75df62fea1b6..44486fd0e883 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -1121,8 +1121,11 @@ int __meminit vmemmap_populate(unsigned long
>> start, unsigned long end, int node,
>> void *p = NULL;
>>
>> p = vmemmap_alloc_block_buf(PMD_SIZE, node, altmap);
>> - if (!p)
>> - return -ENOMEM;
>> + if (!p) {
>> + if (vmemmap_populate_basepages(addr, next, node, altmap))
>> + return -ENOMEM;
>> + continue;
>> + }
>>
>> pmd_set_huge(pmdp, __pa(p), __pgprot(PROT_SECT_NORMAL));
>> } else
>>
Sudarshan
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
Linux Foundation Collaborative Project