On Fri, Sep 29, 2017 at 7:08 AM, Kirill A. Shutemov <[email protected]> wrote: > With boot-time switching between paging mode we will have variable > MAX_PHYSMEM_BITS. > > Let's use the maximum variable possible for CONFIG_X86_5LEVEL=y > configuration to define zsmalloc data structures. > > The patch introduces MAX_POSSIBLE_PHYSMEM_BITS to cover such case. > It also suits well to handle PAE special case. > > Signed-off-by: Kirill A. Shutemov <[email protected]> > Cc: Minchan Kim <[email protected]> > Cc: Nitin Gupta <[email protected]> > Cc: Sergey Senozhatsky <[email protected]> > --- > arch/x86/include/asm/pgtable-3level_types.h | 1 + > arch/x86/include/asm/pgtable_64_types.h | 2 ++ > mm/zsmalloc.c | 13 +++++++------ > 3 files changed, 10 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/include/asm/pgtable-3level_types.h > b/arch/x86/include/asm/pgtable-3level_types.h > index b8a4341faafa..3fe1d107a875 100644 > --- a/arch/x86/include/asm/pgtable-3level_types.h > +++ b/arch/x86/include/asm/pgtable-3level_types.h > @@ -43,5 +43,6 @@ typedef union { > */ > #define PTRS_PER_PTE 512 > > +#define MAX_POSSIBLE_PHYSMEM_BITS 36 > > #endif /* _ASM_X86_PGTABLE_3LEVEL_DEFS_H */ > diff --git a/arch/x86/include/asm/pgtable_64_types.h > b/arch/x86/include/asm/pgtable_64_types.h > index 06470da156ba..39075df30b8a 100644 > --- a/arch/x86/include/asm/pgtable_64_types.h > +++ b/arch/x86/include/asm/pgtable_64_types.h > @@ -39,6 +39,8 @@ typedef struct { pteval_t pte; } pte_t; > #define P4D_SIZE (_AC(1, UL) << P4D_SHIFT) > #define P4D_MASK (~(P4D_SIZE - 1)) > > +#define MAX_POSSIBLE_PHYSMEM_BITS 52 > + > #else /* CONFIG_X86_5LEVEL */ > > /* > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c > index 7c38e850a8fc..7bde01c55c90 100644 > --- a/mm/zsmalloc.c > +++ b/mm/zsmalloc.c > @@ -82,18 +82,19 @@ > * This is made more complicated by various memory models and PAE. > */ > > -#ifndef MAX_PHYSMEM_BITS > -#ifdef CONFIG_HIGHMEM64G > -#define MAX_PHYSMEM_BITS 36 > -#else /* !CONFIG_HIGHMEM64G */ > +#ifndef MAX_POSSIBLE_PHYSMEM_BITS > +#ifdef MAX_PHYSMEM_BITS > +#define MAX_POSSIBLE_PHYSMEM_BITS MAX_PHYSMEM_BITS > +#else > /* > * If this definition of MAX_PHYSMEM_BITS is used, OBJ_INDEX_BITS will just > * be PAGE_SHIFT > */ > -#define MAX_PHYSMEM_BITS BITS_PER_LONG > +#define MAX_POSSIBLE_PHYSMEM_BITS BITS_PER_LONG > #endif > #endif > -#define _PFN_BITS (MAX_PHYSMEM_BITS - PAGE_SHIFT) > + > +#define _PFN_BITS (MAX_POSSIBLE_PHYSMEM_BITS - PAGE_SHIFT) >
I think we can avoid using this new constant in zsmalloc. The reason for trying to save on MAX_PHYSMEM_BITS is just to gain more bits for OBJ_INDEX_BITS which would reduce ZS_MIN_ALLOC_SIZE. However, for all practical values of ZS_MAX_PAGES_PER_ZSPAGE, this min size would remain 32 bytes. So, we can unconditionally use MAX_PHYSMEM_BITS = BITS_PER_LONG and thus OBJ_INDEX_BITS = PAGE_SHIFT. - Nitin
