Re: [PATCH V13 4/4] LoongArch: Enable ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP

[Huacai Chen <chenhuacai@kernel.org>]

Hi, Ren,

On Mon, Oct 24, 2022 at 4:04 PM Guo Ren <guoren@kernel.org> wrote:
>
> On Mon, Oct 24, 2022 at 3:05 PM Huacai Chen <chenhuacai@loongson.cn> wrote:
> >
> > From: Feiyang Chen <chenfeiyang@loongson.cn>
> >
> > The feature of minimizing overhead of struct page associated with each
> > HugeTLB page is implemented on x86_64. However, the infrastructure of
> > this feature is already there, so just select ARCH_WANT_HUGETLB_PAGE_
> > OPTIMIZE_VMEMMAP is enough to enable this feature for LoongArch.
> >
> > To avoid the following build error on LoongArch we should include linux/
> > static_key.h in page-flags.h. This is straightforward but the build
> > error is implicitly a LoongArch-specific problem, because ARM64 and X86
> > have already include static_key.h from their arch-specific core headers.
> >
> > In file included from ./include/linux/mmzone.h:22,
> > from ./include/linux/gfp.h:6,
> > from ./include/linux/mm.h:7,
> > from arch/loongarch/kernel/asm-offsets.c:9:
> > ./include/linux/page-flags.h:208:1: warning: data definition has no
> > type or storage class
> > 208 | DECLARE_STATIC_KEY_MAYBE(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON,
> > | ^~~~~~~~~~~~~~~~~~~~~~~~
> > ./include/linux/page-flags.h:208:1: error: type defaults to 'int' in
> > declaration of 'DECLARE_STATIC_KEY_MAYBE' [-Werror=implicit-int]
> > ./include/linux/page-flags.h:209:26: warning: parameter names (without
> > types) in function declaration
> > 209 | hugetlb_optimize_vmemmap_key);
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > ./include/linux/page-flags.h: In function 'hugetlb_optimize_vmemmap_enabled':
> > ./include/linux/page-flags.h:213:16: error: implicit declaration of
> > function 'static_branch_maybe' [-Werror=implicit-function-declaration]
> > 213 | return static_branch_maybe(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON,
> > | ^~~~~~~~~~~~~~~~~~~
> > ./include/linux/page-flags.h:213:36: error:
> > 'CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON' undeclared (first
> > use in this function); did you mean
> > 'CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP'?
> > 213 | return static_branch_maybe(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON,
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > | CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
> > ./include/linux/page-flags.h:213:36: note: each undeclared identifier
> > is reported only once for each function it appears in
> > ./include/linux/page-flags.h:214:37: error:
> > 'hugetlb_optimize_vmemmap_key' undeclared (first use in this
> > function); did you mean 'hugetlb_optimize_vmemmap_enabled'?
> > 214 | &hugetlb_optimize_vmemmap_key);
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > | hugetlb_optimize_vmemmap_enabled
> >
> > Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> > Signed-off-by: Feiyang Chen <chenfeiyang@loongson.cn>
> > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> > ---
> >  arch/loongarch/Kconfig     | 1 +
> >  include/linux/page-flags.h | 1 +
> >  2 files changed, 2 insertions(+)
> >
> > diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> > index 6f7fa0c0ca08..0a6ef613124c 100644
> > --- a/arch/loongarch/Kconfig
> > +++ b/arch/loongarch/Kconfig
> > @@ -52,6 +52,7 @@ config LOONGARCH
> >         select ARCH_USE_QUEUED_RWLOCKS
> >         select ARCH_USE_QUEUED_SPINLOCKS
> >         select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
> > +       select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
> >         select ARCH_WANT_LD_ORPHAN_WARN
> >         select ARCH_WANTS_NO_INSTR
> >         select BUILDTIME_TABLE_SORT
> > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> > index 0b0ae5084e60..1aafdc73e399 100644
> > --- a/include/linux/page-flags.h
> > +++ b/include/linux/page-flags.h
> > @@ -9,6 +9,7 @@
> >  #include <linux/types.h>
> >  #include <linux/bug.h>
> >  #include <linux/mmdebug.h>
> > +#include <linux/static_key.h>
> Em... riscv needn't this.
I found that after 36d4b36b69590fed99356a4426c940a25 (" lib/nodemask:
inline next_node_in() and node_random()"), build errors have gone. But
I think this is just an accident. Because that commit adds random.h
inclusion in nodemask.h, then asm-offsets.c --> sched.h --> nodemask.h
--> random.h --> once.h --> jump_label.h. If one day this chain is
adjusted, then build errors come again.

On the other hand, page-flags.h is obviously using some static_key
macros, including static_key.h is straightforward for building.

Huacai



Huacai
>
> >  #ifndef __GENERATING_BOUNDS_H
> >  #include <linux/mm_types.h>
> >  #include <generated/bounds.h>
> > --
> > 2.31.1
> >
>
>
> --
> Best Regards
>  Guo Ren
>