From: "gaoliming" <gaoliming@byosoft.com.cn>
To: "'Ankur Arora'" <ankur.a.arora@oracle.com>, <devel@edk2.groups.io>
Cc: "'Michael D Kinney'" <michael.d.kinney@intel.com>,
"'Laszlo Ersek'" <lersek@redhat.com>
Subject: 回复: [RESEND v2] MdePkg: use CpuPause() in CpuDeadLoop()
Date: Mon, 22 Mar 2021 09:40:02 +0800 [thread overview]
Message-ID: <002401d71ebc$4767d130$d6377390$@byosoft.com.cn> (raw)
In-Reply-To: <20210319181421.2791425-1-ankur.a.arora@oracle.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>
Thanks
Liming
> -----邮件原件-----
> 发件人: Ankur Arora <ankur.a.arora@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.arora@oracle.com>; Liming Gao
> <gaoliming@byosoft.com.cn>; Michael D Kinney
> <michael.d.kinney@intel.com>; Laszlo Ersek <lersek@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 <gaoliming@byosoft.com.cn>
> Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
> Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>
> Reviewed-by: Laszlo Ersek <lersek@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
next prev parent reply other threads:[~2021-03-22 1:40 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-19 18:14 [RESEND v2] MdePkg: use CpuPause() in CpuDeadLoop() Ankur Arora
2021-03-22 1:40 ` gaoliming [this message]
[not found] ` <166E86818BEFA632.26767@groups.io>
2021-03-25 3:15 ` 回复: [edk2-devel] 回复: " gaoliming
2021-03-25 18:13 ` Ankur Arora
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