Re: [PATCH] MdePkg: Code optimization to SMM InternalAllocateAlignedPages

["Ni, Ray" <ray.ni@intel.com>]

Dun,
I can understand what you are trying to describe in the commit message.
I have some suggestions/questions that might help you refine the commit message a bit better.

Code changes look good to me.

Thanks,
Ray
> -----Original Message-----
> From: Tan, Dun <dun.tan@intel.com>
> Sent: Thursday, May 18, 2023 2:37 PM
> To: devel@edk2.groups.io
> Cc: Ni, Ray <ray.ni@intel.com>; Kinney, Michael D
> <michael.d.kinney@intel.com>; Gao, Liming <gaoliming@byosoft.com.cn>; Liu,
> Zhiguang <zhiguang.liu@intel.com>
> Subject: [PATCH] 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 the
> allocated 4 pages. If the limit address is already 8KB aligned, then
1. What's "limit address"?

> 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 lower address, then the higher 2 pages cann't be merged
> 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 limit
> of allocated 3 pages is 8KB-aligned, then the last 8K range will
2. What's "last 8k"?