I don't know why the FFS file is cached. Without knowing the reason of caching,
I cannot say it's good to remove the caching logic.
I will let @Gao, Liming, @Kinney, Michael D to comment.
> -----Original Message-----
> From: Ard Biesheuvel <a...@kernel.org>
> Sent: Monday, May 29, 2023 6:17 PM
> To: devel@edk2.groups.io
> Cc: Ard Biesheuvel <a...@kernel.org>; Ni, Ray <ray...@intel.com>; Yao, Jiewen
> <jiewen....@intel.com>; Gerd Hoffmann <kra...@redhat.com>; Taylor Beebe
> <t...@taylorbeebe.com>; Oliver Smith-Denny <o...@smith-denny.com>; Bi, Dandan
> <dandan...@intel.com>; Gao, Liming <gaolim...@byosoft.com.cn>; Kinney,
> Michael D <michael.d.kin...@intel.com>; Leif Lindholm
> <quic_llind...@quicinc.com>; Michael Kubacki <mikub...@linux.microsoft.com>
> Subject: [RFC PATCH 04/11] MdeModulePkg/DxeCore: Avoid caching memory
> mapped FFS files
>
> If a firmware volume is memory mapped, it means we can access it
> contents directly, and so caching serves little purpose beyond
> potentially a minor performance improvement. However, given that most
> files are read only a single time, and dispatched from a decompressed
> firmware volume in DRAM, we can just avoid the redundant caching here.
>
> Signed-off-by: Ard Biesheuvel <a...@kernel.org>
> ---
> MdeModulePkg/Core/Dxe/FwVol/FwVolRead.c | 22 --------------------
> 1 file changed, 22 deletions(-)
>
> diff --git a/MdeModulePkg/Core/Dxe/FwVol/FwVolRead.c
> b/MdeModulePkg/Core/Dxe/FwVol/FwVolRead.c
> index 2ff22c93aad48d7e..69df96685d680868 100644
> --- a/MdeModulePkg/Core/Dxe/FwVol/FwVolRead.c
> +++ b/MdeModulePkg/Core/Dxe/FwVol/FwVolRead.c
> @@ -284,7 +284,6 @@ FvReadFile (
> UINT8 *SrcPtr;
>
> EFI_FFS_FILE_HEADER *FfsHeader;
>
> UINTN InputBufferSize;
>
> - UINTN WholeFileSize;
>
>
>
> if (NameGuid == NULL) {
>
> return EFI_INVALID_PARAMETER;
>
> @@ -316,27 +315,6 @@ FvReadFile (
> // Get a pointer to the header
>
> //
>
> FfsHeader = FvDevice->LastKey->FfsHeader;
>
> - if (FvDevice->IsMemoryMapped) {
>
> - //
>
> - // Memory mapped FV has not been cached, so here is to cache by file.
>
> - //
>
> - if (!FvDevice->LastKey->FileCached) {
>
> - //
>
> - // Cache FFS file to memory buffer.
>
> - //
>
> - WholeFileSize = IS_FFS_FILE2 (FfsHeader) ? FFS_FILE2_SIZE (FfsHeader) :
> FFS_FILE_SIZE (FfsHeader);
>
> - FfsHeader = AllocateCopyPool (WholeFileSize, FfsHeader);
>
> - if (FfsHeader == NULL) {
>
> - return EFI_OUT_OF_RESOURCES;
>
> - }
>
> -
>
> - //
>
> - // Let FfsHeader in FfsFileEntry point to the cached file buffer.
>
> - //
>
> - FvDevice->LastKey->FfsHeader = FfsHeader;
>
> - FvDevice->LastKey->FileCached = TRUE;
>
> - }
>
> - }
>
>
>
> //
>
> // Remember callers buffer size
>
> --
> 2.39.2
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