Hi Experts,
We are using the 'AllocateAlignedPages' function (inside
'MdePkg/Library/UefiMemoryAllocationLib/MemoryAllocationLib.c')
to allocate 512MB aligned memory chunk in a DXE driver.
However the memory chunk which gets allocated by this API is around 1GB.
I understand that this might be because of the memory fragmentation, as a
result of which allocating
the 512MB aligned buffer might result in memory chunk being allocated be
greater in size than 512MB.
Are we using the right API for the purpose - is there another API available
which allows alignment to specified
more granularly?
Here is the 'AllocateAlignedPages' function which calls
'InternalAllocateAlignedPages' internally.
/**
Allocates one or more 4KB pages of type EfiBootServicesData at a specified
alignment.
Allocates the number of 4KB pages specified by Pages of type
EfiBootServicesData with an
alignment specified by Alignment. The allocated buffer is returned. If
Pages is 0, then NULL is
returned. If there is not enough memory at the specified alignment remaining
to satisfy the
request, then NULL is returned.
If Alignment is not a power of two and Alignment is not zero, then ASSERT().
If Pages plus EFI_SIZE_TO_PAGES (Alignment) overflows, then ASSERT().
@param Pages The number of 4 KB pages to allocate.
@param Alignment The requested alignment of the allocation.
Must be a power of two.
If Alignment is zero, then byte alignment is
used.
@return A pointer to the allocated buffer or NULL if allocation fails.
**/
VOID *
EFIAPI
AllocateAlignedPages (
IN UINTN Pages,
IN UINTN Alignment
)
{
return InternalAllocateAlignedPages (EfiBootServicesData, Pages, Alignment);
}
...
/**
Allocates one or more 4KB pages of a certain memory type at a specified
alignment.
Allocates the number of 4KB pages specified by Pages of a certain memory type
with an alignment
specified by Alignment. The allocated buffer is returned. If Pages is 0,
then NULL is returned.
If there is not enough memory at the specified alignment remaining to satisfy
the request, then
NULL is returned.
If Alignment is not a power of two and Alignment is not zero, then ASSERT().
If Pages plus EFI_SIZE_TO_PAGES (Alignment) overflows, then ASSERT().
@param MemoryType The type of memory to allocate.
@param Pages The number of 4 KB pages to allocate.
@param Alignment The requested alignment of the allocation.
Must be a power of two.
If Alignment is zero, then byte alignment is
used.
@return A pointer to the allocated buffer or NULL if allocation fails.
**/
VOID *
InternalAllocateAlignedPages (
IN EFI_MEMORY_TYPE MemoryType,
IN UINTN Pages,
IN UINTN Alignment
)
...
Thanks for the help.
Regards,
Bhupesh
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