The patch titled
Subject: Makefile: extend 32B aligned debug option to 64B aligned
has been added to the -mm tree. Its filename is
makefile-extend-32b-aligned-debug-option-to-64b-aligned.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/makefile-extend-32b-aligned-debug-option-to-64b-aligned.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/makefile-extend-32b-aligned-debug-option-to-64b-aligned.patch
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------------------------------------------------------
From: Feng Tang <feng.tang@xxxxxxxxx>
Subject: Makefile: extend 32B aligned debug option to 64B aligned
commit 09c60546f04f ("./Makefile: add debug option to enable function
aligned on 32 bytes") was introduced to help debugging strange kernel
performance changes caused by code alignment change.
Recently we found 2 similar cases [1][2] caused by code-alignment changes,
which can only be identified by forcing 64 bytes aligned for all
functions.
Originally, 32 bytes was used mainly for not wasting too much text space,
but this option is only for debug anyway where text space is not a big
concern. So extend the alignment to 64 bytes to cover more similar cases.
[1].https://lore.kernel.org/lkml/20210427090013.GG32408@xsang-OptiPlex-9020/
[2].https://lore.kernel.org/lkml/20210420030837.GB31773@xsang-OptiPlex-9020/
Link: https://lkml.kernel.org/r/1620286499-40999-1-git-send-email-feng.tang@xxxxxxxxx
Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Cc: Michal Marek <michal.lkml@xxxxxxxxxxx>
Cc: Andi Kleen <andi.kleen@xxxxxxxxx>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Makefile | 4 ++--
lib/Kconfig.debug | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)
--- a/lib/Kconfig.debug~makefile-extend-32b-aligned-debug-option-to-64b-aligned
+++ a/lib/Kconfig.debug
@@ -400,8 +400,8 @@ config SECTION_MISMATCH_WARN_ONLY
If unsure, say Y.
-config DEBUG_FORCE_FUNCTION_ALIGN_32B
- bool "Force all function address 32B aligned" if EXPERT
+config DEBUG_FORCE_FUNCTION_ALIGN_64B
+ bool "Force all function address 64B aligned" if EXPERT
help
There are cases that a commit from one domain changes the function
address alignment of other domains, and cause magic performance
--- a/Makefile~makefile-extend-32b-aligned-debug-option-to-64b-aligned
+++ a/Makefile
@@ -953,8 +953,8 @@ KBUILD_CFLAGS += $(CC_FLAGS_CFI)
export CC_FLAGS_CFI
endif
-ifdef CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_32B
-KBUILD_CFLAGS += -falign-functions=32
+ifdef CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_64B
+KBUILD_CFLAGS += -falign-functions=64
endif
# arch Makefile may override CC so keep this after arch Makefile is included
_
Patches currently in -mm which might be from feng.tang@xxxxxxxxx are
makefile-extend-32b-aligned-debug-option-to-64b-aligned.patch
