[PATCH v2 09/10] OvmfPkg: disable list length checks in NOOPT and DEBUG builds

["Laszlo Ersek" <lersek@redhat.com>]

In NOOPT and DEBUG builds, if "PcdMaximumLinkedListLength" is nonzero,
then several LIST_ENTRY *node* APIs in BaseLib compare the *full* list
length against the PCD.

This turns the time complexity of node-level APIs from constant to linear,
and that of full-list manipulations from linear to quadratic.

As an example, consider the EFI_SHELL_FILE_INFO list, which is a data
structure that's widely used in the UEFI shell. I randomly extracted 5000
files from "/usr/include" on my laptop, spanning 1095 subdirectories out
of 1538, and then ran "DIR -R" in the UEFI shell on this tree. These are
the wall-clock times:

           PcdMaximumLinkedListLength  PcdMaximumLinkedListLength
           =1,000,000                  =0
           --------------------------  ---------------------------
FAT        4 min 31 s                        18 s
virtio-fs  5 min 13 s                  1 min 33 s

Checking list lengths against an arbitrary maximum (default: 1,000,000)
seems useless even in NOOPT and DEBUG builds, while the cost is
significant; so set the PCD to 0.

Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Julien Grall <julien@xen.org>
Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Peter Grehan <grehan@freebsd.org>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Cc: Rebecca Cran <rebecca@bsdio.com>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3152
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
---

Notes:
    v2:
    - no changes
    - pick up Ard's A-b

 OvmfPkg/AmdSev/AmdSevX64.dsc | 1 +
 OvmfPkg/Bhyve/BhyveX64.dsc   | 1 +
 OvmfPkg/OvmfPkgIa32.dsc      | 1 +
 OvmfPkg/OvmfPkgIa32X64.dsc   | 1 +
 OvmfPkg/OvmfPkgX64.dsc       | 1 +
 OvmfPkg/OvmfXen.dsc          | 1 +
 6 files changed, 6 insertions(+)

diff --git a/OvmfPkg/AmdSev/AmdSevX64.dsc b/OvmfPkg/AmdSev/AmdSevX64.dsc
index dad8635c3388..e6d545ab522f 100644
--- a/OvmfPkg/AmdSev/AmdSevX64.dsc
+++ b/OvmfPkg/AmdSev/AmdSevX64.dsc
@@ -441,6 +441,7 @@ [PcdsFixedAtBuild]
   gEfiMdeModulePkgTokenSpaceGuid.PcdStatusCodeMemorySize|1
   gEfiMdeModulePkgTokenSpaceGuid.PcdResetOnMemoryTypeInformationChange|FALSE
   gEfiMdePkgTokenSpaceGuid.PcdMaximumGuidedExtractHandler|0x10
+  gEfiMdePkgTokenSpaceGuid.PcdMaximumLinkedListLength|0
 !if ($(FD_SIZE_IN_KB) == 1024) || ($(FD_SIZE_IN_KB) == 2048)
   gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x2000
   gEfiMdeModulePkgTokenSpaceGuid.PcdMaxAuthVariableSize|0x2800
diff --git a/OvmfPkg/Bhyve/BhyveX64.dsc b/OvmfPkg/Bhyve/BhyveX64.dsc
index 33edf3d2d6b5..a1f43eaa4d9c 100644
--- a/OvmfPkg/Bhyve/BhyveX64.dsc
+++ b/OvmfPkg/Bhyve/BhyveX64.dsc
@@ -431,6 +431,7 @@ [PcdsFixedAtBuild]
   gEfiMdeModulePkgTokenSpaceGuid.PcdStatusCodeMemorySize|1
   gEfiMdeModulePkgTokenSpaceGuid.PcdResetOnMemoryTypeInformationChange|FALSE
   gEfiMdePkgTokenSpaceGuid.PcdMaximumGuidedExtractHandler|0x10
+  gEfiMdePkgTokenSpaceGuid.PcdMaximumLinkedListLength|0
 !if ($(FD_SIZE_IN_KB) == 1024) || ($(FD_SIZE_IN_KB) == 2048)
   gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x2000
   gEfiMdeModulePkgTokenSpaceGuid.PcdMaxAuthVariableSize|0x2800
diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
index 8b6dbb834505..e5184ef06731 100644
--- a/OvmfPkg/OvmfPkgIa32.dsc
+++ b/OvmfPkg/OvmfPkgIa32.dsc
@@ -478,6 +478,7 @@ [PcdsFixedAtBuild]
   gEfiMdeModulePkgTokenSpaceGuid.PcdResetOnMemoryTypeInformationChange|FALSE
 !endif
   gEfiMdePkgTokenSpaceGuid.PcdMaximumGuidedExtractHandler|0x10
+  gEfiMdePkgTokenSpaceGuid.PcdMaximumLinkedListLength|0
 !if ($(FD_SIZE_IN_KB) == 1024) || ($(FD_SIZE_IN_KB) == 2048)
   gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x2000
   gEfiMdeModulePkgTokenSpaceGuid.PcdMaxAuthVariableSize|0x2800
diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
index 4d7a26636a72..3bfec9196eba 100644
--- a/OvmfPkg/OvmfPkgIa32X64.dsc
+++ b/OvmfPkg/OvmfPkgIa32X64.dsc
@@ -482,6 +482,7 @@ [PcdsFixedAtBuild]
   gEfiMdeModulePkgTokenSpaceGuid.PcdResetOnMemoryTypeInformationChange|FALSE
 !endif
   gEfiMdePkgTokenSpaceGuid.PcdMaximumGuidedExtractHandler|0x10
+  gEfiMdePkgTokenSpaceGuid.PcdMaximumLinkedListLength|0
 !if ($(FD_SIZE_IN_KB) == 1024) || ($(FD_SIZE_IN_KB) == 2048)
   gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x2000
   gEfiMdeModulePkgTokenSpaceGuid.PcdMaxAuthVariableSize|0x2800
diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index 10f6a64d7f47..1376158e37e3 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -484,6 +484,7 @@ [PcdsFixedAtBuild]
   gEfiMdeModulePkgTokenSpaceGuid.PcdResetOnMemoryTypeInformationChange|FALSE
 !endif
   gEfiMdePkgTokenSpaceGuid.PcdMaximumGuidedExtractHandler|0x10
+  gEfiMdePkgTokenSpaceGuid.PcdMaximumLinkedListLength|0
 !if ($(FD_SIZE_IN_KB) == 1024) || ($(FD_SIZE_IN_KB) == 2048)
   gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x2000
   gEfiMdeModulePkgTokenSpaceGuid.PcdMaxAuthVariableSize|0x2800
diff --git a/OvmfPkg/OvmfXen.dsc b/OvmfPkg/OvmfXen.dsc
index 7d31e88907ca..f3fe85d57209 100644
--- a/OvmfPkg/OvmfXen.dsc
+++ b/OvmfPkg/OvmfXen.dsc
@@ -358,6 +358,7 @@ [PcdsFixedAtBuild]
   gEfiMdeModulePkgTokenSpaceGuid.PcdStatusCodeMemorySize|1
   gEfiMdeModulePkgTokenSpaceGuid.PcdResetOnMemoryTypeInformationChange|FALSE
   gEfiMdePkgTokenSpaceGuid.PcdMaximumGuidedExtractHandler|0x10
+  gEfiMdePkgTokenSpaceGuid.PcdMaximumLinkedListLength|0
 !if ($(FD_SIZE_IN_KB) == 1024) || ($(FD_SIZE_IN_KB) == 2048)
   gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x2000
   gEfiMdeModulePkgTokenSpaceGuid.PcdMaxAuthVariableSize|0x2800
-- 
2.19.1.3.g30247aa5d201