[PATCH 09/10] powerpc/mm/slice: use the dynamic high slice size to limit bitmap operations
Christophe LEROY
christophe.leroy at c-s.fr
Wed Mar 7 02:02:20 AEDT 2018
Le 06/03/2018 à 14:25, Nicholas Piggin a écrit :
> The number of high slices a process might use now depends on its
> address space size, and what allocation address it has requested.
>
> This patch uses that limit throughout call chains where possible,
> rather than use the fixed SLICE_NUM_HIGH for bitmap operations.
> This saves some cost for processes that don't use very large address
> spaces.
>
> Perormance numbers aren't changed significantly, this may change
> with larger address spaces or different mmap access patterns that
> require more slice mask building.
>
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
> ---
> arch/powerpc/mm/slice.c | 75 +++++++++++++++++++++++++++++--------------------
> 1 file changed, 45 insertions(+), 30 deletions(-)
>
> diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
> index 086c31b8b982..507d17e2cfcd 100644
> --- a/arch/powerpc/mm/slice.c
> +++ b/arch/powerpc/mm/slice.c
> @@ -61,14 +61,12 @@ static void slice_print_mask(const char *label, const struct slice_mask *mask) {
> #endif
>
> static void slice_range_to_mask(unsigned long start, unsigned long len,
> - struct slice_mask *ret)
> + struct slice_mask *ret,
> + unsigned long high_slices)
> {
> unsigned long end = start + len - 1;
>
> ret->low_slices = 0;
> - if (SLICE_NUM_HIGH)
> - bitmap_zero(ret->high_slices, SLICE_NUM_HIGH);
> -
> if (start < SLICE_LOW_TOP) {
> unsigned long mend = min(end,
> (unsigned long)(SLICE_LOW_TOP - 1));
> @@ -77,6 +75,10 @@ static void slice_range_to_mask(unsigned long start, unsigned long len,
> - (1u << GET_LOW_SLICE_INDEX(start));
> }
>
> + if (!SLICE_NUM_HIGH)
> + return;
> +
> + bitmap_zero(ret->high_slices, high_slices);
In include/linux/bitmap.h, it is said:
* Note that nbits should be always a compile time evaluable constant.
* Otherwise many inlines will generate horrible code.
Not sure that's true, but it is written ...
> if ((start + len) > SLICE_LOW_TOP) {
> unsigned long start_index = GET_HIGH_SLICE_INDEX(start);
> unsigned long align_end = ALIGN(end, (1UL << SLICE_HIGH_SHIFT));
> @@ -120,22 +122,20 @@ static int slice_high_has_vma(struct mm_struct *mm, unsigned long slice)
> }
>
> static void slice_mask_for_free(struct mm_struct *mm, struct slice_mask *ret,
> - unsigned long high_limit)
> + unsigned long high_slices)
> {
> unsigned long i;
>
> ret->low_slices = 0;
> - if (SLICE_NUM_HIGH)
> - bitmap_zero(ret->high_slices, SLICE_NUM_HIGH);
> -
> for (i = 0; i < SLICE_NUM_LOW; i++)
> if (!slice_low_has_vma(mm, i))
> ret->low_slices |= 1u << i;
>
> - if (high_limit <= SLICE_LOW_TOP)
> + if (!SLICE_NUM_HIGH || !high_slices)
> return;
>
> - for (i = 0; i < GET_HIGH_SLICE_INDEX(high_limit); i++)
> + bitmap_zero(ret->high_slices, high_slices);
> + for (i = 0; i < high_slices; i++)
> if (!slice_high_has_vma(mm, i))
> __set_bit(i, ret->high_slices);
> }
> @@ -232,6 +232,7 @@ static void slice_convert(struct mm_struct *mm,
> {
> int index, mask_index;
> /* Write the new slice psize bits */
> + unsigned long high_slices;
> unsigned char *hpsizes, *lpsizes;
> struct slice_mask *psize_mask, *old_mask;
> unsigned long i, flags;
> @@ -267,7 +268,8 @@ static void slice_convert(struct mm_struct *mm,
> }
>
> hpsizes = mm->context.high_slices_psize;
> - for (i = 0; i < GET_HIGH_SLICE_INDEX(mm->context.slb_addr_limit); i++) {
> + high_slices = GET_HIGH_SLICE_INDEX(mm->context.slb_addr_limit);
> + for (i = 0; SLICE_NUM_HIGH && i < high_slices; i++) {
> if (!test_bit(i, mask->high_slices))
> continue;
>
> @@ -434,32 +436,37 @@ static unsigned long slice_find_area(struct mm_struct *mm, unsigned long len,
> }
>
> static inline void slice_copy_mask(struct slice_mask *dst,
> - const struct slice_mask *src)
> + const struct slice_mask *src,
> + unsigned long high_slices)
> {
> dst->low_slices = src->low_slices;
> if (!SLICE_NUM_HIGH)
> return;
> - bitmap_copy(dst->high_slices, src->high_slices, SLICE_NUM_HIGH);
> + bitmap_copy(dst->high_slices, src->high_slices, high_slices);
> }
>
> static inline void slice_or_mask(struct slice_mask *dst,
> const struct slice_mask *src1,
> - const struct slice_mask *src2)
> + const struct slice_mask *src2,
> + unsigned long high_slices)
> {
> dst->low_slices = src1->low_slices | src2->low_slices;
> if (!SLICE_NUM_HIGH)
> return;
> - bitmap_or(dst->high_slices, src1->high_slices, src2->high_slices, SLICE_NUM_HIGH);
> + bitmap_or(dst->high_slices, src1->high_slices, src2->high_slices,
> + high_slices);
Why a new line here, this line is shorter than before.
Or that was forgotten in a previous patch ?
> }
>
> static inline void slice_andnot_mask(struct slice_mask *dst,
> const struct slice_mask *src1,
> - const struct slice_mask *src2)
> + const struct slice_mask *src2,
> + unsigned long high_slices)
> {
> dst->low_slices = src1->low_slices & ~src2->low_slices;
> if (!SLICE_NUM_HIGH)
> return;
> - bitmap_andnot(dst->high_slices, src1->high_slices, src2->high_slices, SLICE_NUM_HIGH);
> + bitmap_andnot(dst->high_slices, src1->high_slices, src2->high_slices,
> + high_slices);
Same comment.
> }
>
> #ifdef CONFIG_PPC_64K_PAGES
> @@ -482,6 +489,7 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
> struct mm_struct *mm = current->mm;
> unsigned long newaddr;
> unsigned long high_limit;
> + unsigned long high_slices;
>
> high_limit = DEFAULT_MAP_WINDOW;
> if (addr >= high_limit || (fixed && (addr + len > high_limit)))
> @@ -498,6 +506,7 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
> return -ENOMEM;
> }
>
> + high_slices = GET_HIGH_SLICE_INDEX(high_limit);
> if (high_limit > mm->context.slb_addr_limit) {
> /*
> * Increasing the slb_addr_limit does not require
> @@ -557,13 +566,13 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
> if (psize == MMU_PAGE_64K) {
> compat_maskp = slice_mask_for_size(mm, MMU_PAGE_4K);
> if (fixed)
> - slice_or_mask(&good_mask, maskp, compat_maskp);
> + slice_or_mask(&good_mask, maskp, compat_maskp, high_slices);
> else
> - slice_copy_mask(&good_mask, maskp);
> + slice_copy_mask(&good_mask, maskp, high_slices);
> } else
> #endif
> {
> - slice_copy_mask(&good_mask, maskp);
> + slice_copy_mask(&good_mask, maskp, high_slices);
> }
> slice_print_mask(" good_mask", &good_mask);
> if (compat_maskp)
> @@ -596,8 +605,8 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
> * We don't fit in the good mask, check what other slices are
> * empty and thus can be converted
> */
> - slice_mask_for_free(mm, &potential_mask, high_limit);
> - slice_or_mask(&potential_mask, &potential_mask, &good_mask);
> + slice_mask_for_free(mm, &potential_mask, high_slices);
> + slice_or_mask(&potential_mask, &potential_mask, &good_mask, high_slices);
> slice_print_mask(" potential", &potential_mask);
>
> if (addr || fixed) {
> @@ -634,7 +643,7 @@ 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_maskp);
> + slice_or_mask(&potential_mask, &potential_mask, compat_maskp, high_slices);
> addr = slice_find_area(mm, len, &potential_mask,
> psize, topdown, high_limit);
> }
> @@ -643,17 +652,17 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
> if (addr == -ENOMEM)
> return -ENOMEM;
>
> - slice_range_to_mask(addr, len, &potential_mask);
> + slice_range_to_mask(addr, len, &potential_mask, high_slices);
> slice_dbg(" found potential area at 0x%lx\n", addr);
> slice_print_mask(" mask", &potential_mask);
>
> convert:
> - slice_andnot_mask(&potential_mask, &potential_mask, &good_mask);
> + slice_andnot_mask(&potential_mask, &potential_mask, &good_mask, high_slices);
> if (compat_maskp && !fixed)
> - slice_andnot_mask(&potential_mask, &potential_mask, compat_maskp);
> + slice_andnot_mask(&potential_mask, &potential_mask, compat_maskp, high_slices);
> if (potential_mask.low_slices ||
> (SLICE_NUM_HIGH &&
> - !bitmap_empty(potential_mask.high_slices, SLICE_NUM_HIGH))) {
> + !bitmap_empty(potential_mask.high_slices, high_slices))) {
Are we sure high_slices is not nul here when SLICE_NUM_HIGH is not nul ?
Christophe
> slice_convert(mm, &potential_mask, psize);
> if (psize > MMU_PAGE_BASE)
> on_each_cpu(slice_flush_segments, mm, 1);
> @@ -727,7 +736,9 @@ void slice_init_new_context_exec(struct mm_struct *mm)
> mm->context.user_psize = psize;
>
> /*
> - * Set all slice psizes to the default.
> + * Set all slice psizes to the default. High slices could
> + * be initialised up to slb_addr_limit if we ensure to
> + * initialise the rest of them as slb_addr_limit is expanded.
> */
> lpsizes = mm->context.low_slices_psize;
> memset(lpsizes, (psize << 4) | psize, SLICE_NUM_LOW >> 1);
> @@ -748,10 +759,12 @@ void slice_set_range_psize(struct mm_struct *mm, unsigned long start,
> unsigned long len, unsigned int psize)
> {
> struct slice_mask mask;
> + unsigned long high_slices;
>
> VM_BUG_ON(radix_enabled());
>
> - slice_range_to_mask(start, len, &mask);
> + high_slices = GET_HIGH_SLICE_INDEX(mm->context.slb_addr_limit);
> + slice_range_to_mask(start, len, &mask, high_slices);
> slice_convert(mm, &mask, psize);
> }
>
> @@ -790,9 +803,11 @@ int is_hugepage_only_range(struct mm_struct *mm, unsigned long addr,
> if (psize == MMU_PAGE_64K) {
> const struct slice_mask *compat_maskp;
> struct slice_mask available;
> + unsigned long high_slices;
>
> compat_maskp = slice_mask_for_size(mm, MMU_PAGE_4K);
> - slice_or_mask(&available, maskp, compat_maskp);
> + high_slices = GET_HIGH_SLICE_INDEX(mm->context.slb_addr_limit);
> + slice_or_mask(&available, maskp, compat_maskp, high_slices);
> return !slice_check_range_fits(mm, &available, addr, len);
> }
> #endif
>
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