Eric,
You are right! I added the missing line back.
Thanks,
Ray
> -----Original Message-----
> From: Ray Ni <niru...@users.noreply.github.com>
> Sent: Friday, April 10, 2020 10:07 AM
> To: devel@edk2.groups.io
> Cc: Ni, Ray <ray...@intel.com>; Dong, Eric <eric.d...@intel.com>; Zeng, Star
> <star.z...@intel.com>
> Subject: [PATCH v2] UefiCpuPkg/PiSmmCpuDxeSmm: Improve the performance of
> GetFreeToken()
>
> Today's GetFreeToken() runs at the algorithm complexity of O(n)
> where n is the size of the token list.
>
> The change introduces a new global variable FirstFreeToken and it
> always points to the first free token. So the algorithm complexity
> of GetFreeToken() decreases from O(n) to O(1).
>
> The improvement matters when some SMI code uses StartupThisAP()
> service for each of the AP such that the algorithm complexity
> becomes O(n) * O(m) where m is the AP count.
>
> As next steps,
> 1. PROCEDURE_TOKEN.Used field can be optimized out because
> all tokens before FirstFreeToken should have "Used" set while all
> after FirstFreeToken should have "Used" cleared.
> 2. ResetTokens() can be optimized to only reset tokens before
> FirstFreeToken.
>
> Signed-off-by: Ray Ni <ray...@intel.com>
> Cc: Eric Dong <eric.d...@intel.com>
> Cc: Star Zeng <star.z...@intel.com>
> ---
> UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c | 73 ++++++++--------------
> UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h | 3 +-
> 2 files changed, 28 insertions(+), 48 deletions(-)
>
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> index c285a70ebb..b3f6c9e6a6 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> @@ -1,7 +1,7 @@
> /** @file
> SMM MP service implementation
>
> -Copyright (c) 2009 - 2020, Intel Corporation. All rights reserved.<BR>
> +Copyright (c) 2009 - 2021, Intel Corporation. All rights reserved.<BR>
> Copyright (c) 2017, AMD Incorporated. All rights reserved.<BR>
>
> SPDX-License-Identifier: BSD-2-Clause-Patent
> @@ -453,6 +453,11 @@ ResetTokens (
>
> Link = GetNextNode (&gSmmCpuPrivate->TokenList, Link);
> }
> +
> + //
> + // Reset the FirstFreeToken to the beginning of token list upon exiting
> SMI.
> + //
> + gSmmCpuPrivate->FirstFreeToken = GetFirstNode (&gSmmCpuPrivate->TokenList);
> }
>
> /**
> @@ -1060,23 +1065,21 @@ IsTokenInUse (
> /**
> Allocate buffer for the SPIN_LOCK and PROCEDURE_TOKEN.
>
> + @return First token of the token buffer.
> **/
> -VOID
> +LIST_ENTRY *
> AllocateTokenBuffer (
> VOID
> )
> {
> UINTN SpinLockSize;
> UINT32 TokenCountPerChunk;
> - UINTN ProcTokenSize;
> UINTN Index;
> - PROCEDURE_TOKEN *ProcToken;
> SPIN_LOCK *SpinLock;
> UINT8 *SpinLockBuffer;
> - UINT8 *ProcTokenBuffer;
> + PROCEDURE_TOKEN *ProcTokens;
>
> SpinLockSize = GetSpinLockProperties ();
> - ProcTokenSize = sizeof (PROCEDURE_TOKEN);
>
> TokenCountPerChunk = FixedPcdGet32 (PcdCpuSmmMpTokenCountPerChunk);
> ASSERT (TokenCountPerChunk != 0);
> @@ -1092,49 +1095,22 @@ AllocateTokenBuffer (
> SpinLockBuffer = AllocatePool (SpinLockSize * TokenCountPerChunk);
> ASSERT (SpinLockBuffer != NULL);
>
> - ProcTokenBuffer = AllocatePool (ProcTokenSize * TokenCountPerChunk);
> - ASSERT (ProcTokenBuffer != NULL);
> + ProcTokens = AllocatePool (sizeof (PROCEDURE_TOKEN) * TokenCountPerChunk);
> + ASSERT (ProcTokens != NULL);
>
> for (Index = 0; Index < TokenCountPerChunk; Index++) {
> SpinLock = (SPIN_LOCK *)(SpinLockBuffer + SpinLockSize * Index);
> InitializeSpinLock (SpinLock);
>
> - ProcToken = (PROCEDURE_TOKEN *)(ProcTokenBuffer + ProcTokenSize * Index);
> - ProcToken->Signature = PROCEDURE_TOKEN_SIGNATURE;
> - ProcToken->SpinLock = SpinLock;
> - ProcToken->Used = FALSE;
> - ProcToken->RunningApCount = 0;
> + ProcTokens[Index].Signature = PROCEDURE_TOKEN_SIGNATURE;
> + ProcTokens[Index].SpinLock = SpinLock;
> + ProcTokens[Index].Used = FALSE;
> + ProcTokens[Index].RunningApCount = 0;
>
> - InsertTailList (&gSmmCpuPrivate->TokenList, &ProcToken->Link);
> + InsertTailList (&gSmmCpuPrivate->TokenList, &ProcTokens[Index].Link);
> }
> -}
>
> -/**
> - Find first free token in the allocated token list.
> -
> - @retval return the first free PROCEDURE_TOKEN.
> -
> -**/
> -PROCEDURE_TOKEN *
> -FindFirstFreeToken (
> - VOID
> - )
> -{
> - LIST_ENTRY *Link;
> - PROCEDURE_TOKEN *ProcToken;
> -
> - Link = GetFirstNode (&gSmmCpuPrivate->TokenList);
> - while (!IsNull (&gSmmCpuPrivate->TokenList, Link)) {
> - ProcToken = PROCEDURE_TOKEN_FROM_LINK (Link);
> -
> - if (!ProcToken->Used) {
> - return ProcToken;
> - }
> -
> - Link = GetNextNode (&gSmmCpuPrivate->TokenList, Link);
> - }
> -
> - return NULL;
> + return &ProcTokens[0].Link;
> }
>
> /**
> @@ -1154,12 +1130,15 @@ GetFreeToken (
> {
> PROCEDURE_TOKEN *NewToken;
>
> - NewToken = FindFirstFreeToken ();
> - if (NewToken == NULL) {
> - AllocateTokenBuffer ();
> - NewToken = FindFirstFreeToken ();
> + //
> + // If FirstFreeToken meets the end of token list, enlarge the token list.
> + // Set FirstFreeToken to the first free token.
> + //
> + if (gSmmCpuPrivate->FirstFreeToken == &gSmmCpuPrivate->TokenList) {
> + gSmmCpuPrivate->FirstFreeToken = AllocateTokenBuffer ();
> }
> - ASSERT (NewToken != NULL);
> + NewToken = PROCEDURE_TOKEN_FROM_LINK (gSmmCpuPrivate->FirstFreeToken);
> + gSmmCpuPrivate->FirstFreeToken = GetNextNode (&gSmmCpuPrivate->TokenList,
> gSmmCpuPrivate->FirstFreeToken);
>
> NewToken->Used = TRUE;
> NewToken->RunningApCount = RunningApsCount;
> @@ -1781,7 +1760,7 @@ InitializeDataForMmMp (
>
> InitializeListHead (&gSmmCpuPrivate->TokenList);
>
> - AllocateTokenBuffer ();
> + gSmmCpuPrivate->FirstFreeToken = AllocateTokenBuffer ();
> }
>
> /**
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> index fe7e8b0323..17f4bd34fa 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> @@ -1,7 +1,7 @@
> /** @file
> Agent Module to load other modules to deploy SMM Entry Vector for X86 CPU.
>
> -Copyright (c) 2009 - 2019, Intel Corporation. All rights reserved.<BR>
> +Copyright (c) 2009 - 2021, Intel Corporation. All rights reserved.<BR>
> Copyright (c) 2017, AMD Incorporated. All rights reserved.<BR>
>
> SPDX-License-Identifier: BSD-2-Clause-Patent
> @@ -255,6 +255,7 @@ typedef struct {
>
> PROCEDURE_WRAPPER *ApWrapperFunc;
> LIST_ENTRY TokenList;
> + LIST_ENTRY *FirstFreeToken;
> } SMM_CPU_PRIVATE_DATA;
>
> extern SMM_CPU_PRIVATE_DATA *gSmmCpuPrivate;
> --
> 2.21.0.windows.1
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