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Commit ae3066bd authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
Browse files

powerpc/mm/slice: implement slice_check_range_fits 



Rather than build slice masks from a range then use that to check for
fit in a candidate mask, implement slice_check_range_fits that checks
if a range fits in a mask directly.

This allows several structures to be removed from stacks, and also we
don't expect a huge range in a lot of these cases, so building and
comparing a full mask is going to be more expensive than testing just
one or two bits of the range.

On POWER8, this increases vfork+exec+exit performance by 0.3%
and reduces time to mmap+munmap a 64kB page by 5%.

Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 5709f7cf

arch/powerpc/mm/slice.c

+34 −28
Original line number Diff line number Diff line
@@ -174,26 +174,36 @@ static struct slice_mask *slice_mask_for_size(struct mm_struct *mm, int psize) 
#error "Must define the slice masks for page sizes supported by the platform"

#endif



static int slice_check_fit(struct mm_struct *mm,

			   const struct slice_mask *mask,

			   const struct slice_mask *available)

static bool slice_check_range_fits(struct mm_struct *mm,

			   const struct slice_mask *available,

			   unsigned long start, unsigned long len)

{

	DECLARE_BITMAP(result, SLICE_NUM_HIGH);

	/*

	 * Make sure we just do bit compare only to the max

	 * addr limit and not the full bit map size.

	 */

	unsigned long slice_count = GET_HIGH_SLICE_INDEX(mm->context.slb_addr_limit);

	unsigned long end = start + len - 1;

	u64 low_slices = 0;



	if (!SLICE_NUM_HIGH)

		return (mask->low_slices & available->low_slices) ==

		       mask->low_slices;

	if (start < SLICE_LOW_TOP) {

		unsigned long mend = min(end,

					 (unsigned long)(SLICE_LOW_TOP - 1));



		low_slices = (1u << (GET_LOW_SLICE_INDEX(mend) + 1))

				- (1u << GET_LOW_SLICE_INDEX(start));

	}

	if ((low_slices & available->low_slices) != low_slices)

		return false;



	if (SLICE_NUM_HIGH && ((start + len) > SLICE_LOW_TOP)) {

		unsigned long start_index = GET_HIGH_SLICE_INDEX(start);

		unsigned long align_end = ALIGN(end, (1UL << SLICE_HIGH_SHIFT));

		unsigned long count = GET_HIGH_SLICE_INDEX(align_end) - start_index;

		unsigned long i;



	bitmap_and(result, mask->high_slices,

		   available->high_slices, slice_count);

		for (i = start_index; i < start_index + count; i++) {

			if (!test_bit(i, available->high_slices))

				return false;

		}

	}



	return (mask->low_slices & available->low_slices) == mask->low_slices &&

		bitmap_equal(result, mask->high_slices, slice_count);

	return true;

}



static void slice_flush_segments(void *parm)
@@ -558,14 +568,10 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len, 


	/* First check hint if it's valid or if we have MAP_FIXED */

	if (addr != 0 || fixed) {

		/* Build a mask for the requested range */

		slice_range_to_mask(addr, len, &mask);

		slice_print_mask(" mask", &mask);



		/* Check if we fit in the good mask. If we do, we just return,

		 * nothing else to do

		 */

		if (slice_check_fit(mm, &mask, &good_mask)) {

		if (slice_check_range_fits(mm, &good_mask, addr, len)) {

			slice_dbg(" fits good !\n");

			return addr;

		}
@@ -591,11 +597,12 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len, 
	slice_or_mask(&potential_mask, &good_mask);

	slice_print_mask(" potential", &potential_mask);



	if ((addr != 0 || fixed) &&

			slice_check_fit(mm, &mask, &potential_mask)) {

	if (addr != 0 || fixed) {

		if (slice_check_range_fits(mm, &potential_mask, addr, len)) {

			slice_dbg(" fits potential !\n");

			goto convert;

		}

	}



	/* If we have MAP_FIXED and failed the above steps, then error out */

	if (fixed)
@@ -772,13 +779,12 @@ void slice_set_range_psize(struct mm_struct *mm, unsigned long start, 
int is_hugepage_only_range(struct mm_struct *mm, unsigned long addr,

			   unsigned long len)

{

	struct slice_mask mask, available;

	struct slice_mask available;

	unsigned int psize = mm->context.user_psize;



	if (radix_enabled())

		return 0;



	slice_range_to_mask(addr, len, &mask);

	available = *slice_mask_for_size(mm, psize);

#ifdef CONFIG_PPC_64K_PAGES

	/* We need to account for 4k slices too */
@@ -795,6 +801,6 @@ int is_hugepage_only_range(struct mm_struct *mm, unsigned long addr, 
	slice_print_mask(" mask", &mask);

	slice_print_mask(" available", &available);

#endif

	return !slice_check_fit(mm, &mask, &available);

	return !slice_check_range_fits(mm, &available, addr, len);

}

#endif