Re: 回复: [edk2-devel] [PATCH v2] MdePkg: use CpuPause() in CpuDeadLoop()
Hi Liming, On 03/19/21 02:04, gaoliming wrote: > Ankur: > Seemly, the patch is missing in this mail. I can see the patch body just fine in my mailbox / list folder. Also, the list archives seem to have it: - https://edk2.groups.io/g/devel/message/73018 - 20210318184504.2745112-1-ankur.a.arora@oracle.com">http://mid.mail-archive.com/20210318184504.2745112-1-ankur.a.arora@oracle.com - https://listman.redhat.com/archives/edk2-devel-archive/2021-March/msg00765.html Ankur, can you post a "RESEND v2" please, anyway? Thanks Laszlo > > Thanks > Liming >> -邮件原件- >> 发件人: devel@edk2.groups.io 代表 Ankur Arora >> 发送时间: 2021年3月19日 2:45 >> 收件人: devel@edk2.groups.io >> 抄送: Ankur Arora ; Liming Gao >> ; Michael D Kinney >> ; Laszlo Ersek >> 主题: [edk2-devel] [PATCH v2] MdePkg: use CpuPause() in CpuDeadLoop() >> >> CpuPause() might allow the CPU to go into a lower power state >> state while we spin. >> >> On X86, CpuPause() executes a PAUSE instruction which the Intel >> and AMD specs describe as follows: >> >> Intel: >> "PAUSE: An additional function of the PAUSE instruction is to reduce >> the power consumed by a processor while executing a spin loop. A >> processor can execute a spin-wait loop extremely quickly, causing the >> processor to consume a lot of power while it waits for the resource it >> is spinning on to become available. Inserting a pause instruction in a >> spin-wait loop greatly reduces the processorb > > -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#73043): https://edk2.groups.io/g/devel/message/73043 Mute This Topic: https://groups.io/mt/81445311/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
回复: [edk2-devel] [PATCH v2] MdePkg: use CpuPause() in CpuDeadLoop()
Ankur: Seemly, the patch is missing in this mail. Thanks Liming > -邮件原件- > 发件人: devel@edk2.groups.io 代表 Ankur Arora > 发送时间: 2021年3月19日 2:45 > 收件人: devel@edk2.groups.io > 抄送: Ankur Arora ; Liming Gao > ; Michael D Kinney > ; Laszlo Ersek > 主题: [edk2-devel] [PATCH v2] MdePkg: use CpuPause() in CpuDeadLoop() > > CpuPause() might allow the CPU to go into a lower power state > state while we spin. > > On X86, CpuPause() executes a PAUSE instruction which the Intel > and AMD specs describe as follows: > > Intel: > "PAUSE: An additional function of the PAUSE instruction is to reduce > the power consumed by a processor while executing a spin loop. A > processor can execute a spin-wait loop extremely quickly, causing the > processor to consume a lot of power while it waits for the resource it > is spinning on to become available. Inserting a pause instruction in a > spin-wait loop greatly reduces the processorb -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#73026): https://edk2.groups.io/g/devel/message/73026 Mute This Topic: https://groups.io/mt/81445311/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
[edk2-devel] [PATCH v2] MdePkg: use CpuPause() in CpuDeadLoop()
CpuPause() might allow the CPU to go into a lower power state state while we spin. On X86, CpuPause() executes a PAUSE instruction which the Intel and AMD specs describe as follows: Intel: "PAUSE: An additional function of the PAUSE instruction is to reduce the power consumed by a processor while executing a spin loop. A processor can execute a spin-wait loop extremely quickly, causing the processor to consume a lot of power while it waits for the resource it is spinning on to become available. Inserting a pause instruction in a spin-wait loop greatly reduces the processorâs power consumption." AMD: "PAUSE: Improves the performance of spin loops, by providing a hint to the processor that the current code is in a spin loop. The processor may use this to optimize power consumption while in the spin loop. Architecturally, this instruction behaves like a NOP instruction." On RISC-V and ARM64, CpuPause() executes a NOP, which is no worse than the tight loop we have. Cc: Liming Gao Signed-off-by: Ankur Arora Reviewed-by: Michael D Kinney Reviewed-by: Laszlo Ersek --- MdePkg/Library/BaseLib/CpuDeadLoop.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/MdePkg/Library/BaseLib/CpuDeadLoop.c b/MdePkg/Library/BaseLib/CpuDeadLoop.c index 9e110cacbc96..3cd304351a65 100644 --- a/MdePkg/Library/BaseLib/CpuDeadLoop.c +++ b/MdePkg/Library/BaseLib/CpuDeadLoop.c @@ -28,5 +28,7 @@ CpuDeadLoop ( { volatile UINTN Index; - for (Index = 0; Index == 0;); + for (Index = 0; Index == 0;) { +CpuPause(); + } } -- 2.9.3 -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#73018): https://edk2.groups.io/g/devel/message/73018 Mute This Topic: https://groups.io/mt/81437102/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-