Reviewed-by: Liming Gao <gaolim...@byosoft.com.cn>
Thanks
Liming
> -----邮件原件-----
> 发件人: Ankur Arora <ankur.a.ar...@oracle.com>
> 发送时间: 2021年3月20日 2:14
> 收件人: devel@edk2.groups.io
> 抄送: Ankur Arora <ankur.a.ar...@oracle.com>; Liming Gao
> <gaolim...@byosoft.com.cn>; Michael D Kinney
> <michael.d.kin...@intel.com>; Laszlo Ersek <ler...@redhat.com>
> 主题: [RESEND 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 processor’s 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 <gaolim...@byosoft.com.cn>
> Signed-off-by: Ankur Arora <ankur.a.ar...@oracle.com>
> Reviewed-by: Michael D Kinney <michael.d.kin...@intel.com>
> Reviewed-by: Laszlo Ersek <ler...@redhat.com>
> ---
> 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 (#73063): https://edk2.groups.io/g/devel/message/73063
Mute This Topic: https://groups.io/mt/81515182/21656
Group Owner: devel+ow...@edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com]
-=-=-=-=-=-=-=-=-=-=-=-
