From ae3066bd1cbe58e596c791f72a36e576df5d9ed1 Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Wed, 7 Mar 2018 11:37:13 +1000 Subject: [PATCH] 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: Nicholas Piggin Signed-off-by: Michael Ellerman --- arch/powerpc/mm/slice.c | 62 ++++++++++++++++++++++------------------- 1 file changed, 34 insertions(+), 28 deletions(-) diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c index 3e199b9cbbfd..0a5efa40e739 100644 --- a/arch/powerpc/mm/slice.c +++ b/arch/powerpc/mm/slice.c @@ -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)); - bitmap_and(result, mask->high_slices, - available->high_slices, slice_count); + 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; - return (mask->low_slices & available->low_slices) == mask->low_slices && - bitmap_equal(result, mask->high_slices, slice_count); + 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; + + for (i = start_index; i < start_index + count; i++) { + if (!test_bit(i, available->high_slices)) + return false; + } + } + + 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; } @@ -591,10 +597,11 @@ 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)) { - slice_dbg(" fits potential !\n"); - goto convert; + 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 */ @@ -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 -- GitLab