On Thu, May 6, 2021 at 4:35 PM Feng Tang <feng.tang@xxxxxxxxx> wrote: > > 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/ > Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx> Applied to linux-kbuild. Thanks. > --- > Makefile | 4 ++-- > lib/Kconfig.debug | 4 ++-- > 2 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/Makefile b/Makefile > index 72af8e4..a9f6715 100644 > --- a/Makefile > +++ b/Makefile > @@ -958,8 +958,8 @@ 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 > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 678c1396..6ce26b8 100644 > --- a/lib/Kconfig.debug > +++ b/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 > -- > 2.7.4 > -- Best Regards Masahiro Yamada