Re: [PATCH v2 01/11] percpu: Introduce percpu hot section
From: Brian Gerst
Date: Wed Feb 26 2025 - 21:10:11 EST
On Wed, Feb 26, 2025 at 2:36 PM Uros Bizjak <ubizjak@xxxxxxxxx> wrote:
>
> On Wed, Feb 26, 2025 at 7:05 PM Brian Gerst <brgerst@xxxxxxxxx> wrote:
> >
> > Add a subsection to the percpu data for frequently accessed variables
> > that should remain cached on each processor. These varables should not
> > be accessed from other processors to avoid cacheline bouncing.
> >
> > This will replace the pcpu_hot struct on x86, and open up similar
> > functionality to other architectures and the kernel core.
> >
> > Signed-off-by: Brian Gerst <brgerst@xxxxxxxxx>
> > ---
> > include/asm-generic/vmlinux.lds.h | 10 ++++++++++
> > include/linux/percpu-defs.h | 12 ++++++++++++
> > 2 files changed, 22 insertions(+)
> >
> > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> > index 92fc06f7da74..92dd6065fd0a 100644
> > --- a/include/asm-generic/vmlinux.lds.h
> > +++ b/include/asm-generic/vmlinux.lds.h
> > @@ -385,6 +385,11 @@ defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG)
> > . = ALIGN(PAGE_SIZE); \
> > __nosave_end = .;
> >
> > +#define CACHE_HOT_DATA(align) \
> > + . = ALIGN(align); \
> > + *(SORT_BY_ALIGNMENT(.data..hot.*)) \
> > + . = ALIGN(align);
> > +
> > #define PAGE_ALIGNED_DATA(page_align) \
> > . = ALIGN(page_align); \
> > *(.data..page_aligned) \
> > @@ -1065,6 +1070,10 @@ defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG)
> > . = ALIGN(PAGE_SIZE); \
> > *(.data..percpu..page_aligned) \
> > . = ALIGN(cacheline); \
> > + __per_cpu_hot_start = .; \
> > + *(SORT_BY_ALIGNMENT(.data..percpu..hot.*)) \
> > + . = ALIGN(cacheline); \
> > + __per_cpu_hot_end = .; \
> > *(.data..percpu..read_mostly) \
> > . = ALIGN(cacheline); \
> > *(.data..percpu) \
> > @@ -1112,6 +1121,7 @@ defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG)
> > INIT_TASK_DATA(inittask) \
> > NOSAVE_DATA \
> > PAGE_ALIGNED_DATA(pagealigned) \
> > + CACLE_HOT_DATA(cacheline) \
>
> There is a typo in the above macro name.
Fixed in the next version.
Brian Gerst