From fcd71642df9a3a5932a2db116acc6fe23458d8f5 Mon Sep 17 00:00:00 2001 From: duntan Date: Thu, 18 May 2023 15:31:01 +0800 Subject: MdePkg: Code optimization to SMM InternalAllocateAlignedPages This commit is code optimization to InternalAllocateAlignedPages of SmmMemoryAllocationLib which can reduce free memory fragments. Also it can reduce one pre-allocation page. Let's take a simple example: The expected pages size is 8KB, Alignment value is 8KB. In original InternalAllocateAlignedPages(), the first step is to allocate 4 pages and then find the first 8KB-aligned address in allocated 4 pages. If the upper limit address of allocated 4 pages is already 8KB aligned, then the allocated 4 pages contains two 8KB-aligned 8KB ranges. The lower 2 pages will be selected and removed from free pages. Then the higher 2 pages will be free. Since the whole memory allocation is from high address to low address, then the higher 2 pages cann't be merged with other free pages, causing the free memory fragments. However, when only allocate 3(2+2-1) pages, we can avoid the free memory fragments in specific case. Also 3 pages must contain a 8KB-aligned 8KB range, which meets the requirement. If the upper limit address of allocated 3 pages is 8KB-aligned, then the higher 2 pages range of allocated 3 pages is 8KB-aligned and will be selected and removed from free pages. The remaining lower one page of allocated 3 pages will be free and merged with left lower free memory. This can reduce free memory fragments in smm. Signed-off-by: Dun Tan Cc: Ray Ni Reviewed-by: Michael D Kinney Cc: Liming Gao Cc: Zhiguang Liu --- MdePkg/Library/SmmMemoryAllocationLib/MemoryAllocationLib.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'MdePkg/Library') diff --git a/MdePkg/Library/SmmMemoryAllocationLib/MemoryAllocationLib.c b/MdePkg/Library/SmmMemoryAllocationLib/MemoryAllocationLib.c index 3ab2c1ebfd..99a8259325 100644 --- a/MdePkg/Library/SmmMemoryAllocationLib/MemoryAllocationLib.c +++ b/MdePkg/Library/SmmMemoryAllocationLib/MemoryAllocationLib.c @@ -322,7 +322,7 @@ InternalAllocateAlignedPages ( // Calculate the total number of pages since alignment is larger than page size. // AlignmentMask = Alignment - 1; - RealPages = Pages + EFI_SIZE_TO_PAGES (Alignment); + RealPages = Pages + EFI_SIZE_TO_PAGES (Alignment) - 1; // // Make sure that Pages plus EFI_SIZE_TO_PAGES (Alignment) does not overflow. // -- cgit v1.2.3