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

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

arch/powerpc/include/asm/mmu-hash64.h

+3 −0
Original line number Diff line number Diff line
@@ -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_ */

arch/powerpc/mm/hash_utils_64.c

+21 −13
Original line number Diff line number Diff line
@@ -609,10 +609,28 @@ static int __init htab_dt_scan_pftsize(unsigned long node, 
	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

	 * 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