UefiCpuPkg/MpInitLib DXE: Add PCD to control AP status check interval

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=2627

The commit will introduce a static PCD to specify the periodic interval
for checking the AP status when MP services StartupAllAPs() and
StartupThisAP() are being executed in a non-blocking manner. Or in other
words, specifies the interval for callback function CheckApsStatus().

The purpose is to provide the platform owners with the ability to choose
the proper interval value to trigger CheckApsStatus() according to:
A) The number of processors in the system;
B) How MP services (StartupAllAPs & StartupThisAP) being used.

Setting the PCD to a small value means the AP status check callback will
be triggered more frequently, it can benefit the performance for the case
when the BSP uses WaitForEvent() or uses CheckEvent() in a loop to wait
for AP(s) to complete the task, especially when the task can be finished
considerably fast on AP(s).

An example is within function CpuFeaturesInitialize() under
UefiCpuPkg/Library/RegisterCpuFeaturesLib/DxeRegisterCpuFeaturesLib.c,
where BSP will perform the same task with APs and requires all the
processors to finish the task before BSP proceeds to its next task.

Setting the PCD to a big value, on the other hand, can reduce the impact
on BSP by the time being consumed in CheckApsStatus(), especially when the
number of processors is huge so that the time consumed in CheckApsStatus()
is not negligible.

The type of the PCD is UINT32, which means the maximum possible interval
value can be set to:
4,294,967,295 microseconds = 4,295 seconds = 71.58 minutes = 1.19 hours
which should be sufficient for usage.

For least impact, the default value of the new PCD will be the same with
the current interval value. It will be set to 100,000 microseconds, which
is 100 milliseconds.

Unitest done:
A) OS boot successfully;
B) Use debug message to confirm the 'TriggerTime' parameter for the
   'SetTimer' service is the same before & after this patch.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Brian J. Johnson <brian.johnson@hpe.com>
Signed-off-by: Hao A Wu <hao.a.wu@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/UefiCpuPkg/UefiCpuPkg.uni b/UefiCpuPkg/UefiCpuPkg.uni
index c0d6ed5136..1780dfdc12 100644
--- a/UefiCpuPkg/UefiCpuPkg.uni
+++ b/UefiCpuPkg/UefiCpuPkg.uni
@@ -3,7 +3,7 @@
 //

 // This Package provides UEFI compatible CPU modules and libraries.

 //

-// Copyright (c) 2007 - 2015, Intel Corporation. All rights reserved.<BR>

+// Copyright (c) 2007 - 2020, Intel Corporation. All rights reserved.<BR>

 //

 // SPDX-License-Identifier: BSD-2-Clause-Patent

 //

@@ -275,3 +275,6 @@
 #string STR_gUefiCpuPkgTokenSpaceGuid_PcdCpuSmmMpTokenCountPerChunk_PROMPT  #language en-US "Specify the count of pre allocated SMM MP tokens per chunk.\n"

 

 #string STR_gUefiCpuPkgTokenSpaceGuid_PcdCpuSmmMpTokenCountPerChunk_HELP    #language en-US "This value used to specify the count of pre allocated SMM MP tokens per chunk.\n"

+

+#string STR_gUefiCpuPkgTokenSpaceGuid_PcdCpuApStatusCheckIntervalInMicroSeconds_PROMPT  #language en-US "Periodic interval value in microseconds for AP status check in DXE.\n"

+#string STR_gUefiCpuPkgTokenSpaceGuid_PcdCpuApStatusCheckIntervalInMicroSeconds_HELP    #language en-US "Periodic interval value in microseconds for the status check of APs for StartupAllAPs() and StartupThisAP() executed in non-blocking mode in DXE phase.\n"