From d262bd5a73998252d1cdf632bedaf1ca540839d8 Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Wed, 7 Mar 2018 11:37:16 +1000 Subject: [PATCH] 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: Nicholas Piggin Signed-off-by: Michael Ellerman --- arch/powerpc/mm/slice.c | 79 ++++++++++++++++++++--------------------- 1 file changed, 38 insertions(+), 41 deletions(-) diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c index c4cb4de1fab5..b3b465c37224 100644 --- a/arch/powerpc/mm/slice.c +++ b/arch/powerpc/mm/slice.c @@ -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_NUM_HIGH && - !bitmap_empty(mask.high_slices, SLICE_NUM_HIGH))) { - slice_convert(mm, &mask, psize); + 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(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