Re: [PATCH v2] UefiCpuPkg/PiSmmCpuDxeSmm: Improve the performance of GetFreeToken()


Zeng, Star
 

Your time is super fast. 😊

-----Original Message-----
From: Ni, Ray <ray.ni@...>
Sent: Friday, April 10, 2020 10:50 AM
To: Dong, Eric <eric.dong@...>; Ray Ni
<niruiyu@...>; devel@edk2.groups.io
Cc: Zeng, Star <star.zeng@...>
Subject: RE: [PATCH v2] UefiCpuPkg/PiSmmCpuDxeSmm: Improve the
performance of GetFreeToken()

My bad. I thought it is 2021 now. let me send v3.

-----Original Message-----
From: Dong, Eric <eric.dong@...>
Sent: Friday, April 10, 2020 10:26 AM
To: Ray Ni <niruiyu@...>; devel@edk2.groups.io
Cc: Ni, Ray <ray.ni@...>; Zeng, Star <star.zeng@...>
Subject: RE: [PATCH v2] UefiCpuPkg/PiSmmCpuDxeSmm: Improve the
performance of GetFreeToken()

Hi Ray,

It still has copyright year issue. Should 2020, not 2021.

Thanks,
Eric
-----Original Message-----
From: Ray Ni <niruiyu@...>
Sent: Friday, April 10, 2020 10:07 AM
To: devel@edk2.groups.io
Cc: Ni, Ray <ray.ni@...>; Dong, Eric <eric.dong@...>;
Zeng, Star <star.zeng@...>
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.ni@...>
Cc: Eric Dong <eric.dong@...>
Cc: Star Zeng <star.zeng@...>
---
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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