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powerpc/mm: Split hash page table sizing heuristic into a helper 

htab_get_table_size() either retrieve the size of the hash page table (HPT)
from the device tree - if the HPT size is determined by firmware - or
uses a heuristic to determine a good size based on RAM size if the kernel
is responsible for allocating the HPT.

To support a PAPR extension allowing resizing of the HPT, we're going to
want the memory size -> HPT size logic elsewhere, so split it out into a
helper function.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
David Gibson 2016-02-09 13:32:43 +10:00 committed by Michael Ellerman
parent 1dace6c665
commit 5c3c7ede2b
2 changed files with 24 additions and 13 deletions
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3
arch/powerpc/include/asm/mmu-hash64.h
View File

@ -608,6 +608,9 @@ static inline unsigned long get_kernel_vsid(unsigned long ea, int ssize)
context = (MAX_USER_CONTEXT) + ((ea >> 60) - 0xc) + 1;
return get_vsid(context, ea, ssize);
}
unsigned htab_shift_for_mem_size(unsigned long mem_size);
#endif /* __ASSEMBLY__ */
#endif /* _ASM_POWERPC_MMU_HASH64_H_ */

34
arch/powerpc/mm/hash_utils_64.c
View File

@ -609,10 +609,28 @@ static int __init htab_dt_scan_pftsize(unsigned long node,
return 0;
}
unsigned htab_shift_for_mem_size(unsigned long mem_size)
{
unsigned memshift = __ilog2(mem_size);
unsigned pshift = mmu_psize_defs[mmu_virtual_psize].shift;
unsigned pteg_shift;
/* round mem_size up to next power of 2 */
if ((1UL << memshift) < mem_size)
memshift += 1;
/* aim for 2 pages / pteg */
pteg_shift = memshift - (pshift + 1);
/*
* 2^11 PTEGS of 128 bytes each, ie. 2^18 bytes is the minimum htab
* size permitted by the architecture.
*/
return max(pteg_shift + 7, 18U);
}
static unsigned long __init htab_get_table_size(void)
{
unsigned long mem_size, rnd_mem_size, pteg_count, psize;
/* If hash size isn't already provided by the platform, we try to
* retrieve it from the device-tree. If it's not there neither, we
* calculate it now based on the total RAM size
@ -622,17 +640,7 @@ static unsigned long __init htab_get_table_size(void)
if (ppc64_pft_size)
return 1UL << ppc64_pft_size;
/* round mem_size up to next power of 2 */
mem_size = memblock_phys_mem_size();
rnd_mem_size = 1UL << __ilog2(mem_size);
if (rnd_mem_size < mem_size)
rnd_mem_size <<= 1;
/* # pages / 2 */
psize = mmu_psize_defs[mmu_virtual_psize].shift;
pteg_count = max(rnd_mem_size >> (psize + 1), 1UL << 11);
return pteg_count << 7;
return 1UL << htab_shift_for_mem_size(memblock_phys_mem_size());
}
#ifdef CONFIG_MEMORY_HOTPLUG