Re: [UNIKRAFT PATCH] arch: Define the cache line size for each architecture

[Simon Kuenzer <simon.kuenzer@xxxxxxxxx>]

Hey,

we should be careful with name spacing. A reason why we prefixed low 
definition like this with `__` (e.g., PAGE_SIZE, PAGE_SHIFT) is that 
those low-level headers get included by a lot of lib headers. We may 
easily run into name clashes. I propose to use __CACHELINE_SIZE instead 
for this header.
Thanks,

Simon

On 23.07.20 13:51, Costin Lupu wrote:
> Reviewed-by: Costin Lupu <costin.lupu@xxxxxxxxx>
>
> On 7/23/20 2:47 PM, Alexander Jung wrote:
> > This definition statically describes the d-cache line size in
> > bytes for {x86_64,arm,arm64}.
> >
> > The d-cache line is a L1 data cache nearest to the processor and
> > the line size refers to the data memory block.
> >
> > The d-line cache size can also be discovered by querying the
> > d-cache build egister at the expense of using more memory and
> > instruction cycles during boot.  Defining this size statically
> > increases performance since it is already known for the
> > respective architecture.
> >
> > Signed-off-by: Alexander Jung <alexander.jung@xxxxxxxxx>
> > ---
> >   arch/arm/arm/include/uk/asm/lcpu.h    | 2 ++
> >   arch/arm/arm64/include/uk/asm/lcpu.h  | 2 ++
> >   arch/x86/x86_64/include/uk/asm/lcpu.h | 2 ++
> >   3 files changed, 6 insertions(+)
> >
> > diff --git a/arch/arm/arm/include/uk/asm/lcpu.h 
> > b/arch/arm/arm/include/uk/asm/lcpu.h
> > index cdeffc3..33f3a6b 100644
> > --- a/arch/arm/arm/include/uk/asm/lcpu.h
> > +++ b/arch/arm/arm/include/uk/asm/lcpu.h
> > @@ -29,6 +29,8 @@
> >   #error Do not include this header directly
> >   #endif
> >   
> > +#define CACHE_LINE_SIZE	32
> > +
> >   struct __regs {
> >         unsigned long r0;
> >         unsigned long r1;
> > diff --git a/arch/arm/arm64/include/uk/asm/lcpu.h 
> > b/arch/arm/arm64/include/uk/asm/lcpu.h
> > index 45d1b23..4597e40 100644
> > --- a/arch/arm/arm64/include/uk/asm/lcpu.h
> > +++ b/arch/arm/arm64/include/uk/asm/lcpu.h
> > @@ -30,6 +30,8 @@
> >   #error Do not include this header directly
> >   #endif
> >   
> > +#define CACHE_LINE_SIZE	64
> > +
> >   #ifdef __ASSEMBLY__
> >   /*
> >    * Stack size to save general purpose registers and essential system
> > diff --git a/arch/x86/x86_64/include/uk/asm/lcpu.h 
> > b/arch/x86/x86_64/include/uk/asm/lcpu.h
> > index 6a471a1..ff137f8 100644
> > --- a/arch/x86/x86_64/include/uk/asm/lcpu.h
> > +++ b/arch/x86/x86_64/include/uk/asm/lcpu.h
> > @@ -32,6 +32,8 @@
> >   #error Do not include this header directly
> >   #endif
> >   
> > +#define CACHE_LINE_SIZE	64
> > +
> >   #ifndef __ASSEMBLY__
> >   struct __regs {
> >         unsigned long pad; /* 8 bytes to make struct size multiple of 16 */