On 7/11/23 11:51 AM, Huang, Ying wrote:
> "Aneesh Kumar K.V" <aneesh.ku...@linux.ibm.com> writes:
>
>> Add a new kconfig option that can be selected if we want to allow
>> pageblock alignment by reserving pages in the vmemmap altmap area.
>> This implies we will be reserving some pages for every memoryblock
>> This also allows the memmap on memory feature to be widely useful
>> with different memory block size values.
>>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
>> ---
>> mm/Kconfig | 9 +++++++
>> mm/memory_hotplug.c | 59 +++++++++++++++++++++++++++++++++++++--------
>> 2 files changed, 58 insertions(+), 10 deletions(-)
>>
>> diff --git a/mm/Kconfig b/mm/Kconfig
>> index 932349271e28..88a1472b2086 100644
>> --- a/mm/Kconfig
>> +++ b/mm/Kconfig
>> @@ -570,6 +570,15 @@ config MHP_MEMMAP_ON_MEMORY
>> depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP
>> depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
>>
>> +config MHP_RESERVE_PAGES_MEMMAP_ON_MEMORY
>> + bool "Allow Reserving pages for page block aligment"
>> + depends on MHP_MEMMAP_ON_MEMORY
>> + help
>> + This option allows memmap on memory feature to be more useful
>> + with different memory block sizes. This is achieved by marking some
>> pages
>> + in each memory block as reserved so that we can get page-block alignment
>> + for the remaining pages.
>> +
>> endif # MEMORY_HOTPLUG
>>
>> config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index 07c99b0cc371..f36aec1f7626 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -1252,15 +1252,17 @@ static inline bool
>> arch_supports_memmap_on_memory(unsigned long size)
>> {
>> unsigned long nr_vmemmap_pages = size >> PAGE_SHIFT;
>> unsigned long vmemmap_size = nr_vmemmap_pages * sizeof(struct page);
>> - unsigned long remaining_size = size - vmemmap_size;
>>
>> - return IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
>> - IS_ALIGNED(remaining_size, (pageblock_nr_pages << PAGE_SHIFT));
>> + return IS_ALIGNED(vmemmap_size, PMD_SIZE);
>> }
>> #endif
>>
>> static bool mhp_supports_memmap_on_memory(unsigned long size)
>> {
>> + unsigned long nr_vmemmap_pages = size >> PAGE_SHIFT;
>> + unsigned long vmemmap_size = nr_vmemmap_pages * sizeof(struct page);
>> + unsigned long remaining_size = size - vmemmap_size;
>> +
>> /*
>> * Besides having arch support and the feature enabled at runtime, we
>> * need a few more assumptions to hold true:
>> @@ -1287,9 +1289,30 @@ static bool mhp_supports_memmap_on_memory(unsigned
>> long size)
>> * altmap as an alternative source of memory, and we do not
>> exactly
>> * populate a single PMD.
>> */
>> - return mhp_memmap_on_memory() &&
>> - size == memory_block_size_bytes() &&
>> - arch_supports_memmap_on_memory(size);
>> + if (!mhp_memmap_on_memory() || size != memory_block_size_bytes())
>> + return false;
>> + /*
>> + * Without page reservation remaining pages should be pageblock
>> aligned.
>> + */
>> + if (!IS_ENABLED(CONFIG_MHP_RESERVE_PAGES_MEMMAP_ON_MEMORY) &&
>> + !IS_ALIGNED(remaining_size, (pageblock_nr_pages << PAGE_SHIFT)))
>> + return false;
>> +
>> + return arch_supports_memmap_on_memory(size);
>> +}
>> +
>> +static inline unsigned long memory_block_align_base(unsigned long size)
>> +{
>> + if (IS_ENABLED(CONFIG_MHP_RESERVE_PAGES_MEMMAP_ON_MEMORY)) {
>> + unsigned long align;
>> + unsigned long nr_vmemmap_pages = size >> PAGE_SHIFT;
>> + unsigned long vmemmap_size;
>> +
>> + vmemmap_size = (nr_vmemmap_pages * sizeof(struct page)) >>
>> PAGE_SHIFT;
>
> DIV_ROUND_UP()?
>
>
yes. Will update.
vmemmap_size = DIV_ROUND_UP(nr_vmemmap_pages * sizeof(struct
page), PAGE_SIZE);
-aneesh
