Reviewed-by: Ray Ni <ray...@intel.com> > -----Original Message----- > From: Tan, Dun <dun....@intel.com> > Sent: Thursday, May 18, 2023 3:31 PM > To: devel@edk2.groups.io > Cc: Ni, Ray <ray...@intel.com>; Kinney, Michael D > <michael.d.kin...@intel.com>; Gao, Liming <gaolim...@byosoft.com.cn>; Liu, > Zhiguang <zhiguang....@intel.com> > Subject: [Patch V2] 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 <dun....@intel.com> > Cc: Ray Ni <ray...@intel.com> > Cc: Michael D Kinney <michael.d.kin...@intel.com> > Cc: Liming Gao <gaolim...@byosoft.com.cn> > Cc: Zhiguang Liu <zhiguang....@intel.com> > --- > MdePkg/Library/SmmMemoryAllocationLib/MemoryAllocationLib.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > 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. > // > -- > 2.31.1.windows.1
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