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SubjectRe: [PATCH v3 2/5] mm: page_alloc: reduce unnecessary binary search in memblock_next_valid_pfn()
On Mon, Mar 26, 2018 at 5:02 AM, Jia He <hejianet@gmail.com> wrote:
> Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns
> where possible") optimized the loop in memmap_init_zone(). But there is
> still some room for improvement. E.g. if pfn and pfn+1 are in the same
> memblock region, we can simply pfn++ instead of doing the binary search
> in memblock_next_valid_pfn. This patch only works when
> CONFIG_HAVE_ARCH_PFN_VALID is enable.
>
> Signed-off-by: Jia He <jia.he@hxt-semitech.com>
> ---
> include/linux/memblock.h | 2 +-
> mm/memblock.c | 73 +++++++++++++++++++++++++++++-------------------
> mm/page_alloc.c | 3 +-
> 3 files changed, 47 insertions(+), 31 deletions(-)
>
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index efbbe4b..a8fb2ab 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -204,7 +204,7 @@ void __next_mem_pfn_range(int *idx, int nid, unsigned long *out_start_pfn,
> #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
>
> #ifdef CONFIG_HAVE_ARCH_PFN_VALID
> -unsigned long memblock_next_valid_pfn(unsigned long pfn);
> +unsigned long memblock_next_valid_pfn(unsigned long pfn, int *idx);
> #endif
>
> /**
> diff --git a/mm/memblock.c b/mm/memblock.c
> index bea5a9c..06c1a08 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -1102,35 +1102,6 @@ void __init_memblock __next_mem_pfn_range(int *idx, int nid,
> *out_nid = r->nid;
> }
>
> -#ifdef CONFIG_HAVE_ARCH_PFN_VALID
> -unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn)
> -{
> - struct memblock_type *type = &memblock.memory;
> - unsigned int right = type->cnt;
> - unsigned int mid, left = 0;
> - phys_addr_t addr = PFN_PHYS(++pfn);
> -
> - do {
> - mid = (right + left) / 2;
> -
> - if (addr < type->regions[mid].base)
> - right = mid;
> - else if (addr >= (type->regions[mid].base +
> - type->regions[mid].size))
> - left = mid + 1;
> - else {
> - /* addr is within the region, so pfn is valid */
> - return pfn;
> - }
> - } while (left < right);
> -
> - if (right == type->cnt)
> - return -1UL;
> - else
> - return PHYS_PFN(type->regions[right].base);
> -}
> -#endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
> -
> /**
> * memblock_set_node - set node ID on memblock regions
> * @base: base of area to set node ID for
> @@ -1162,6 +1133,50 @@ int __init_memblock memblock_set_node(phys_addr_t base, phys_addr_t size,
> }
> #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
>
> +#ifdef CONFIG_HAVE_ARCH_PFN_VALID
> +unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn,
> + int *last_idx)
> +{
> + struct memblock_type *type = &memblock.memory;
> + unsigned int right = type->cnt;
> + unsigned int mid, left = 0;
> + unsigned long start_pfn, end_pfn;
> + phys_addr_t addr = PFN_PHYS(++pfn);
> +
> + /* fast path, return pfh+1 if next pfn is in the same region */
> + if (*last_idx != -1) {
> + start_pfn = PFN_DOWN(type->regions[*last_idx].base);
> + end_pfn = PFN_DOWN(type->regions[*last_idx].base +
> + type->regions[*last_idx].size);
> +
> + if (pfn < end_pfn && pfn > start_pfn)
> + return pfn;
> + }
> +
> + /* slow path, do the binary searching */
> + do {
> + mid = (right + left) / 2;
> +
> + if (addr < type->regions[mid].base)
> + right = mid;
> + else if (addr >= (type->regions[mid].base +
> + type->regions[mid].size))
> + left = mid + 1;
> + else {
> + *last_idx = mid;
> + return pfn;
> + }
> + } while (left < right);
> +
> + if (right == type->cnt)
> + return -1UL;
> +
> + *last_idx = right;
> +
> + return PHYS_PFN(type->regions[*last_idx].base);
> +}
> +#endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
> +
> static phys_addr_t __init memblock_alloc_range_nid(phys_addr_t size,
> phys_addr_t align, phys_addr_t start,
> phys_addr_t end, int nid, ulong flags)
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 2a967f7..0bb0274 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5459,6 +5459,7 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
> unsigned long end_pfn = start_pfn + size;
> pg_data_t *pgdat = NODE_DATA(nid);
> unsigned long pfn;
> + int idx = -1;
> unsigned long nr_initialised = 0;
> struct page *page;
> #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
> @@ -5490,7 +5491,7 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
> * end_pfn), such that we hit a valid pfn (or end_pfn)
> * on our next iteration of the loop.
> */
> - pfn = memblock_next_valid_pfn(pfn) - 1;
> + pfn = memblock_next_valid_pfn(pfn, &idx) - 1;
> #endif
> continue;
> }
> --
> 2.7.4
>

So the function is only defined with CONFIG_HAVE_ARCH_PFN_VALID but
it's called with CONFIG_HAVE_MEMBLOCK_NODE_MAP? The definition should
likely depend on both options as the function really depends on both
conditions. Otherwise it should be defined nop.

--nX

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