[edk2-devel] [PATCH v3 1/4] UefiCpuPkg/MpInitLib: Use XADD to avoid lock acquire/release
Dong, Eric
eric.dong at intel.com
Mon Feb 22 09:06:44 UTC 2021
Reviewed-by: Eric Dong <eric.dong at intel.com>
-----Original Message-----
From: Ni, Ray <ray.ni at intel.com>
Sent: Tuesday, February 9, 2021 10:17 PM
To: devel at edk2.groups.io
Cc: Dong, Eric <eric.dong at intel.com>; Laszlo Ersek <lersek at redhat.com>; Kumar, Rahul1 <rahul1.kumar at intel.com>
Subject: [PATCH v3 1/4] UefiCpuPkg/MpInitLib: Use XADD to avoid lock acquire/release
When AP firstly wakes up, MpFuncs.nasm contains below logic to assign an unique ApIndex to each AP according to who comes first:
---ASM---
TestLock:
xchg [edi], eax
cmp eax, NotVacantFlag
jz TestLock
mov ecx, esi
add ecx, ApIndexLocation
inc dword [ecx]
mov ebx, [ecx]
Releaselock:
mov eax, VacantFlag
xchg [edi], eax
---ASM END---
"lock inc" cannot be used to increase ApIndex because not only the global ApIndex should be increased, but also the result should be stored to a local general purpose register EBX.
This patch learns from the NASM implementation of
InternalSyncIncrement() to use "XADD" instruction which can increase the global ApIndex and store the original ApIndex to EBX in one instruction.
With this patch, OVMF when running in a 255 threads QEMU spends about one second to wakeup all APs. Original implementation needs more than
10 seconds.
Signed-off-by: Ray Ni <ray.ni at intel.com>
Cc: Eric Dong <eric.dong at intel.com>
Cc: Laszlo Ersek <lersek at redhat.com>
Cc: Rahul Kumar <rahul1.kumar at intel.com>
---
.../Library/MpInitLib/Ia32/MpFuncs.nasm | 20 ++++++-------------
UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm | 18 ++++++-----------
2 files changed, 12 insertions(+), 26 deletions(-)
diff --git a/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm b/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm
index 7e81d24aa6..2eaddc93bc 100644
--- a/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm
+++ b/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm
@@ -1,5 +1,5 @@
;------------------------------------------------------------------------------ ;-; Copyright (c) 2015 - 2019, Intel Corporation. All rights reserved.<BR>+; Copyright (c) 2015 - 2021, Intel Corporation. All rights reserved.<BR> ; SPDX-License-Identifier: BSD-2-Clause-Patent ; ; Module Name:@@ -125,19 +125,11 @@ SkipEnableExecuteDisable:
add edi, LockLocation mov eax, NotVacantFlag -TestLock:- xchg [edi], eax- cmp eax, NotVacantFlag- jz TestLock-- mov ecx, esi- add ecx, ApIndexLocation- inc dword [ecx]- mov ebx, [ecx]--Releaselock:- mov eax, VacantFlag- xchg [edi], eax+ mov edi, esi+ add edi, ApIndexLocation+ mov ebx, 1+ lock xadd dword [edi], ebx ; EBX = ApIndex+++ inc ebx ; EBX is CpuNumber mov edi, esi add edi, StackSizeLocationdiff --git a/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm b/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
index aecfd07bc0..5b588f2dcb 100644
--- a/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
+++ b/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
@@ -1,5 +1,5 @@
;------------------------------------------------------------------------------ ;-; Copyright (c) 2015 - 2019, Intel Corporation. All rights reserved.<BR>+; Copyright (c) 2015 - 2021, Intel Corporation. All rights reserved.<BR> ; SPDX-License-Identifier: BSD-2-Clause-Patent ; ; Module Name:@@ -161,18 +161,12 @@ LongModeStart:
add edi, LockLocation mov rax, NotVacantFlag -TestLock:- xchg qword [edi], rax- cmp rax, NotVacantFlag- jz TestLock-- lea ecx, [esi + ApIndexLocation]- inc dword [ecx]- mov ebx, [ecx]+ mov edi, esi+ add edi, ApIndexLocation+ mov ebx, 1+ lock xadd dword [edi], ebx ; EBX = ApIndex+++ inc ebx ; EBX is CpuNumber -Releaselock:- mov rax, VacantFlag- xchg qword [edi], rax ; program stack mov edi, esi add edi, StackSizeLocation--
2.27.0.windows.1
-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#71926): https://edk2.groups.io/g/devel/message/71926
Mute This Topic: https://groups.io/mt/80504936/1813853
Group Owner: devel+owner at edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/unsub [edk2-devel-archive at redhat.com]
-=-=-=-=-=-=-=-=-=-=-=-
More information about the edk2-devel-archive
mailing list