On 06/11/2014 03:23 AM, Li Zhong wrote:
> This patch implements vmemmap_list_free() for vmemmap_free().
>
> The freed entries will be removed from vmemmap_list, and form a freed list,
> with next as the header. The next position in the last allocated page is kept
> at the list tail.
>
> When allocation, if there are freed entries left, get it from the freed list;
> if no freed entries left, get it like before from the last allocated pages.
>
> With this change, realmode_pfn_to_page() also needs to be changed to walk
> all the entries in the vmemmap_list, as the virt_addr of the entries might not
> be stored in order anymore.
>
> It helps to reuse the memory when continuous doing memory hot-plug/remove
> operations, but didn't reclaim the pages already allocated, so the memory
> usage
> will only increase, but won't exceed the value for the largest memory
> configuration.
>
> Signed-off-by: Li Zhong <zh...@linux.vnet.ibm.com>
> Cc: Nathan Fontenot <nf...@linux.vnet.ibm.com>
Acked-by: Nathan Fontenot <nf...@linux.vnet.ibm.com>
> ---
> arch/powerpc/mm/init_64.c | 62
> +++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 52 insertions(+), 10 deletions(-)
>
> diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
> index e3734ed..fa5d28b 100644
> --- a/arch/powerpc/mm/init_64.c
> +++ b/arch/powerpc/mm/init_64.c
> @@ -226,14 +226,24 @@ static void __meminit vmemmap_create_mapping(unsigned
> long start,
> #endif /* CONFIG_PPC_BOOK3E */
>
> struct vmemmap_backing *vmemmap_list;
> +static struct vmemmap_backing *next;
> +static int num_left;
> +static int num_freed;
>
> static __meminit struct vmemmap_backing * vmemmap_list_alloc(int node)
> {
> - static struct vmemmap_backing *next;
> - static int num_left;
> + struct vmemmap_backing *vmem_back;
> + /* get from freed entries first */
> + if (num_freed) {
> + num_freed--;
> + vmem_back = next;
> + next = next->list;
> +
> + return vmem_back;
> + }
>
> /* allocate a page when required and hand out chunks */
> - if (!next || !num_left) {
> + if (!num_left) {
> next = vmemmap_alloc_block(PAGE_SIZE, node);
> if (unlikely(!next)) {
> WARN_ON(1);
> @@ -266,6 +276,38 @@ static __meminit void vmemmap_list_populate(unsigned
> long phys,
> vmemmap_list = vmem_back;
> }
>
> +static unsigned long vmemmap_list_free(unsigned long start)
> +{
> + struct vmemmap_backing *vmem_back, *vmem_back_prev;
> +
> + vmem_back_prev = vmem_back = vmemmap_list;
> +
> + /* look for it with prev pointer recorded */
> + for (; vmem_back; vmem_back = vmem_back->list) {
> + if (vmem_back->virt_addr == start)
> + break;
> + vmem_back_prev = vmem_back;
> + }
> +
> + if (unlikely(!vmem_back)) {
> + WARN_ON(1);
> + return 0;
> + }
> +
> + /* remove it from vmemmap_list */
> + if (vmem_back == vmemmap_list) /* remove head */
> + vmemmap_list = vmem_back->list;
> + else
> + vmem_back_prev->list = vmem_back->list;
> +
> + /* next point to this freed entry */
> + vmem_back->list = next;
> + next = vmem_back;
> + num_freed++;
> +
> + return vmem_back->phys;
> +}
> +
> int __meminit vmemmap_populate(unsigned long start, unsigned long end, int
> node)
> {
> unsigned long page_size = 1 << mmu_psize_defs[mmu_vmemmap_psize].shift;
> @@ -331,16 +373,16 @@ struct page *realmode_pfn_to_page(unsigned long pfn)
> if (pg_va < vmem_back->virt_addr)
> continue;
>
> - /* Check that page struct is not split between real pages */
> - if ((pg_va + sizeof(struct page)) >
> - (vmem_back->virt_addr + page_size))
> - return NULL;
> -
> - page = (struct page *) (vmem_back->phys + pg_va -
> + /* After vmemmap_list entry free is possible, need check all */
> + if ((pg_va + sizeof(struct page)) <=
> + (vmem_back->virt_addr + page_size)) {
> + page = (struct page *) (vmem_back->phys + pg_va -
> vmem_back->virt_addr);
> - return page;
> + return page;
> + }
> }
>
> + /* Probably that page struct is split between real pages */
> return NULL;
> }
> EXPORT_SYMBOL_GPL(realmode_pfn_to_page);
>
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