On Tue, Jun 03, 2014 at 04:47:52PM -0700, David Daney wrote:
> On 06/03/2014 03:47 PM, Ralf Baechle wrote:
> >>--- a/arch/mips/include/asm/addrspace.h
> >>+++ b/arch/mips/include/asm/addrspace.h
> >>@@ -51,8 +51,14 @@
> >> * Returns the physical address of a CKSEGx / XKPHYS address
> >> */
> >> #define CPHYSADDR(a) ((_ACAST32_(a)) & 0x1fffffff)
> >>+#ifndef CONFIG_NUMA
> >> #define XPHYSADDR(a) ((_ACAST64_(a)) &
> >> \
> >> _CONST64_(0x000000ffffffffff))
> >>+#define XPHYSADDR(a) ((_ACAST64_(a)) &
> >>+ _CONST64_(0x0000ffffffffffff))
> >The mask in XPHYSADDR is a function of the processor architecture, not
> >imlementation, not NUMA. The latest version of the MIPS architecture
> >permits PABITS to be as large as 49 bits, so the mask should be
> >0x0001ffffffffffff. Always.
> >>diff --git a/arch/mips/include/asm/sparsemem.h
> >>index d2da53c..c001a90 100644
> >>--- a/arch/mips/include/asm/sparsemem.h
> >>+++ b/arch/mips/include/asm/sparsemem.h
> >>@@ -11,7 +11,12 @@
> >> #else
> >> # define SECTION_SIZE_BITS 28
> >> #endif
> >>+#ifdef CONFIG_NUMA
> >>+#define MAX_PHYSMEM_BITS 48
> >> #define MAX_PHYSMEM_BITS 35
> >Essentially the same comment as for XPHYSADDR above.
> Are you saying to change it to 49 unconditionally for all configurations?
> That would work for OCTEON too, where we have had to increase it to 42.
> What are the implications for kernel data structures if this is set
> many orders of magnitude greater than the actual number of bits used
> on a system?
Shouldn't make a significant difference; the value is used to compute certain
limits in sparse.c and a bitmap in zsmalloc.c which is used only when
CONFIG_ZSMALLOC is enabled.
A more important value which I haven't noticed the Looongson patches to
modify is SECTION_SIZE_BITS in <asm/sparsemem.h>:
#if defined(CONFIG_MIPS_HUGE_TLB_SUPPORT) && defined(CONFIG_PAGE_SIZE_64KB)
# define SECTION_SIZE_BITS 29
# define SECTION_SIZE_BITS 28
Don't ask me why its definition depends on MIPS_HUGE_TLB_SUPPORT and
PAGE_SIZE_64KB - the value describes the larges chunk of contiguous
memory (that is for example memory per node) and that doesn't depend
on these CONFIG_* symbols.