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Commit d262bd5a authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
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powerpc/mm/slice: Use const pointers to cached slice masks where possible 



The slice_mask cache was a basic conversion which copied the slice
mask into caller's structures, because that's how the original code
worked. In most cases the pointer can be used directly instead, saving
a copy and an on-stack structure.

On POWER8, this increases vfork+exec+exit performance by 0.3%
and reduces time to mmap+munmap a 64kB page by 2%.

Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 74907558

arch/powerpc/mm/slice.c

+38 −41
Original line number Diff line number Diff line
@@ -468,10 +468,10 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len, 
				      unsigned long flags, unsigned int psize,

				      int topdown)

{

	struct slice_mask mask;

	struct slice_mask good_mask;

	struct slice_mask potential_mask;

	struct slice_mask compat_mask;

	const struct slice_mask *maskp;

	const struct slice_mask *compat_maskp = NULL;

	int fixed = (flags & MAP_FIXED);

	int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);

	unsigned long page_size = 1UL << pshift;
@@ -505,22 +505,6 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len, 
		on_each_cpu(slice_flush_segments, mm, 1);

	}



	/*

	 * init different masks

	 */

	mask.low_slices = 0;



	/* silence stupid warning */;

	potential_mask.low_slices = 0;



	compat_mask.low_slices = 0;



	if (SLICE_NUM_HIGH) {

		bitmap_zero(mask.high_slices, SLICE_NUM_HIGH);

		bitmap_zero(potential_mask.high_slices, SLICE_NUM_HIGH);

		bitmap_zero(compat_mask.high_slices, SLICE_NUM_HIGH);

	}



	/* Sanity checks */

	BUG_ON(mm->task_size == 0);

	BUG_ON(mm->context.slb_addr_limit == 0);
@@ -543,8 +527,7 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len, 
	/* First make up a "good" mask of slices that have the right size

	 * already

	 */

	good_mask = *slice_mask_for_size(mm, psize);

	slice_print_mask(" good_mask", &good_mask);

	maskp = slice_mask_for_size(mm, psize);



	/*

	 * Here "good" means slices that are already the right page size,
@@ -565,14 +548,24 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len, 
	 *	search in good | compat | free, found => convert free.

	 */



#ifdef CONFIG_PPC_64K_PAGES

	/* If we support combo pages, we can allow 64k pages in 4k slices */

	if (psize == MMU_PAGE_64K) {

		compat_mask = *slice_mask_for_size(mm, MMU_PAGE_4K);

	/*

	 * If we support combo pages, we can allow 64k pages in 4k slices

	 * The mask copies could be avoided in most cases here if we had

	 * a pointer to good mask for the next code to use.

	 */

	if (IS_ENABLED(CONFIG_PPC_64K_PAGES) && psize == MMU_PAGE_64K) {

		compat_maskp = slice_mask_for_size(mm, MMU_PAGE_4K);

		if (fixed)

			slice_or_mask(&good_mask, &good_mask, &compat_mask);

			slice_or_mask(&good_mask, maskp, compat_maskp);

		else

			slice_copy_mask(&good_mask, maskp);

	} else {

		slice_copy_mask(&good_mask, maskp);

	}

#endif



	slice_print_mask(" good_mask", &good_mask);

	if (compat_maskp)

		slice_print_mask(" compat_mask", compat_maskp);



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

	if (addr != 0 || fixed) {
@@ -639,7 +632,7 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len, 
#ifdef CONFIG_PPC_64K_PAGES

	if (addr == -ENOMEM && psize == MMU_PAGE_64K) {

		/* retry the search with 4k-page slices included */

		slice_or_mask(&potential_mask, &potential_mask, &compat_mask);

		slice_or_mask(&potential_mask, &potential_mask, compat_maskp);

		addr = slice_find_area(mm, len, &potential_mask,

				       psize, topdown, high_limit);

	}
@@ -648,17 +641,18 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len, 
	if (addr == -ENOMEM)

		return -ENOMEM;



	slice_range_to_mask(addr, len, &mask);

	slice_range_to_mask(addr, len, &potential_mask);

	slice_dbg(" found potential area at 0x%lx\n", addr);

	slice_print_mask(" mask", &mask);

	slice_print_mask(" mask", &potential_mask);



 convert:

	slice_andnot_mask(&mask, &mask, &good_mask);

	slice_andnot_mask(&mask, &mask, &compat_mask);

	if (mask.low_slices ||

	slice_andnot_mask(&potential_mask, &potential_mask, &good_mask);

	if (compat_maskp && !fixed)

		slice_andnot_mask(&potential_mask, &potential_mask, compat_maskp);

	if (potential_mask.low_slices ||

		(SLICE_NUM_HIGH &&

	     !bitmap_empty(mask.high_slices, SLICE_NUM_HIGH))) {

		slice_convert(mm, &mask, psize);

		 !bitmap_empty(potential_mask.high_slices, SLICE_NUM_HIGH))) {

		slice_convert(mm, &potential_mask, psize);

		if (psize > MMU_PAGE_BASE)

			on_each_cpu(slice_flush_segments, mm, 1);

	}
@@ -787,22 +781,25 @@ 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 available;

	const struct slice_mask *maskp;

	unsigned int psize = mm->context.user_psize;



	if (radix_enabled())

		return 0;



	available = *slice_mask_for_size(mm, psize);

	maskp = slice_mask_for_size(mm, psize);

#ifdef CONFIG_PPC_64K_PAGES

	/* We need to account for 4k slices too */

	if (psize == MMU_PAGE_64K) {

		struct slice_mask compat_mask;

		compat_mask = *slice_mask_for_size(mm, MMU_PAGE_4K);

		slice_or_mask(&available, &available, &compat_mask);

		const struct slice_mask *compat_maskp;

		struct slice_mask available;



		compat_maskp = slice_mask_for_size(mm, MMU_PAGE_4K);

		slice_or_mask(&available, maskp, compat_maskp);

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

	}

#endif



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

	return !slice_check_range_fits(mm, maskp, addr, len);

}

#endif