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ArmVirtPkg: disable list length checks in NOOPT and DEBUG builds 

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.

(See some example OVMF numbers in the previous patch.)

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

Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Julien Grall <julien@xen.org>
Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.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>
Message-Id: <20210113085453.10168-11-lersek@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
This commit is contained in:
Laszlo Ersek 2021-01-13 09:54:53 +01:00 committed by mergify[bot]
parent d3f3c94201
commit 6e55868631
1 changed files with 1 additions and 1 deletions
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2
ArmVirtPkg/ArmVirt.dsc.inc
View File

@ -290,7 +290,7 @@
[PcdsFixedAtBuild.common]
gEfiMdePkgTokenSpaceGuid.PcdMaximumUnicodeStringLength|1000000
gEfiMdePkgTokenSpaceGuid.PcdMaximumAsciiStringLength|1000000
gEfiMdePkgTokenSpaceGuid.PcdMaximumLinkedListLength|1000000
gEfiMdePkgTokenSpaceGuid.PcdMaximumLinkedListLength|0
gEfiMdePkgTokenSpaceGuid.PcdSpinLockTimeout|10000000
gEfiMdePkgTokenSpaceGuid.PcdUefiLibMaxPrintBufferSize|320