Commit 5c3c7ede authored by David Gibson's avatar David Gibson Committed by Michael Ellerman

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: default avatarDavid Gibson <david@gibson.dropbear.id.au>
Reviewed-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 1dace6c6
...@@ -608,6 +608,9 @@ static inline unsigned long get_kernel_vsid(unsigned long ea, int ssize) ...@@ -608,6 +608,9 @@ static inline unsigned long get_kernel_vsid(unsigned long ea, int ssize)
context = (MAX_USER_CONTEXT) + ((ea >> 60) - 0xc) + 1; context = (MAX_USER_CONTEXT) + ((ea >> 60) - 0xc) + 1;
return get_vsid(context, ea, ssize); return get_vsid(context, ea, ssize);
} }
unsigned htab_shift_for_mem_size(unsigned long mem_size);
#endif /* __ASSEMBLY__ */ #endif /* __ASSEMBLY__ */
#endif /* _ASM_POWERPC_MMU_HASH64_H_ */ #endif /* _ASM_POWERPC_MMU_HASH64_H_ */
...@@ -609,10 +609,28 @@ static int __init htab_dt_scan_pftsize(unsigned long node, ...@@ -609,10 +609,28 @@ static int __init htab_dt_scan_pftsize(unsigned long node,
return 0; return 0;
} }
static unsigned long __init htab_get_table_size(void) unsigned htab_shift_for_mem_size(unsigned long mem_size)
{ {
unsigned long mem_size, rnd_mem_size, pteg_count, psize; 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)
{
/* If hash size isn't already provided by the platform, we try to /* 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 * retrieve it from the device-tree. If it's not there neither, we
* calculate it now based on the total RAM size * calculate it now based on the total RAM size
...@@ -622,17 +640,7 @@ static unsigned long __init htab_get_table_size(void) ...@@ -622,17 +640,7 @@ static unsigned long __init htab_get_table_size(void)
if (ppc64_pft_size) if (ppc64_pft_size)
return 1UL << ppc64_pft_size; return 1UL << ppc64_pft_size;
/* round mem_size up to next power of 2 */ return 1UL << htab_shift_for_mem_size(memblock_phys_mem_size());
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;
} }
#ifdef CONFIG_MEMORY_HOTPLUG #ifdef CONFIG_MEMORY_HOTPLUG
......
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