Hi Mike and Liming,
Could you please help to review this patch?
Thanks,
Dun
-----Original Message-----
From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of duntan
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: [edk2-devel] [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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