MdePkg/Library/BaseLib/CpuDeadLoop.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
Use CpuPause() to allow the CPU to go into a lower power state
state while we spin wait.
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>
---
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
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Ankur: Can you give the detail usage for the lower power state when enter into CpuDeadLoop()? Thanks Liming > -----邮件原件----- > 发件人: Ankur Arora <ankur.a.arora@oracle.com> > 发送时间: 2021年3月17日 6:59 > 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> > 主题: [PATCH] MdePkg: use CpuPause() in CpuDeadLoop() > > Use CpuPause() to allow the CPU to go into a lower power state > state while we spin wait. > > 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> > --- > 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 (#72940): https://edk2.groups.io/g/devel/message/72940 Mute This Topic: https://groups.io/mt/81393215/1787277 Group Owner: devel+owner@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [importer@patchew.org] -=-=-=-=-=-=-=-=-=-=-=-
On 2021-03-16 6:08 p.m., gaoliming wrote: > Ankur: > Can you give the detail usage for the lower power state when enter into > CpuDeadLoop()? I'm not really familiar with ARM and RiscV, both of which also have implementations for CpuPause(), for the details for X86 variants are below. From Intel's instruction-set reference: "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." And, from AMD's instruction-set reference: "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." Happy to add this to the commit message if you think it'll be useful. Thanks Ankur > > Thanks > Liming >> -----邮件原件----- >> 发件人: Ankur Arora <ankur.a.arora@oracle.com> >> 发送时间: 2021年3月17日 6:59 >> 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> >> 主题: [PATCH] MdePkg: use CpuPause() in CpuDeadLoop() >> >> Use CpuPause() to allow the CPU to go into a lower power state >> state while we spin wait. >> >> 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> >> --- >> 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 (#72949): https://edk2.groups.io/g/devel/message/72949 Mute This Topic: https://groups.io/mt/81393215/1787277 Group Owner: devel+owner@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [importer@patchew.org] -=-=-=-=-=-=-=-=-=-=-=-
On 03/16/21 23:59, Ankur Arora wrote: > Use CpuPause() to allow the CPU to go into a lower power state > state while we spin wait. > > 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> > --- > 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(); > + } > } > Reviewed-by: Laszlo Ersek <lersek@redhat.com> (for RISC-V and ARM64, the implementations seem to be "nop" instructions) Thanks Laszlo -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#72977): https://edk2.groups.io/g/devel/message/72977 Mute This Topic: https://groups.io/mt/81390478/1787277 Group Owner: devel+owner@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [importer@patchew.org] -=-=-=-=-=-=-=-=-=-=-=-
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