[RFC PATCH v4 11/13] memory-hotplug : free memmap of sparse-vmemmap
Wen Congyang
wency at cn.fujitsu.com
Thu Jul 19 20:01:48 EST 2012
At 07/19/2012 05:45 PM, Wen Congyang Wrote:
> At 07/18/2012 06:16 PM, Yasuaki Ishimatsu Wrote:
>> All pages of virtual mapping in removed memory cannot be freed, since some pages
>> used as PGD/PUD includes not only removed memory but also other memory. So the
>> patch checks whether page can be freed or not.
>>
>> How to check whether page can be freed or not?
>> 1. When removing memory, the page structs of the revmoved memory are filled
>> with 0FD.
>> 2. All page structs are filled with 0xFD on PT/PMD, PT/PMD can be cleared.
>> In this case, the page used as PT/PMD can be freed.
>>
>> Applying patch, __remove_section() of CONFIG_SPARSEMEM_VMEMMAP is integrated
>> into one. So __remove_section() of CONFIG_SPARSEMEM_VMEMMAP is deleted.
>>
>> CC: David Rientjes <rientjes at google.com>
>> CC: Jiang Liu <liuj97 at gmail.com>
>> CC: Len Brown <len.brown at intel.com>
>> CC: Benjamin Herrenschmidt <benh at kernel.crashing.org>
>> CC: Paul Mackerras <paulus at samba.org>
>> CC: Christoph Lameter <cl at linux.com>
>> Cc: Minchan Kim <minchan.kim at gmail.com>
>> CC: Andrew Morton <akpm at linux-foundation.org>
>> CC: KOSAKI Motohiro <kosaki.motohiro at jp.fujitsu.com>
>> CC: Wen Congyang <wency at cn.fujitsu.com>
>> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki at jp.fujitsu.com>
>>
>> ---
>> arch/x86/mm/init_64.c | 121 ++++++++++++++++++++++++++++++++++++++++++++++++++
>> include/linux/mm.h | 2
>> mm/memory_hotplug.c | 19 -------
>> mm/sparse.c | 5 +-
>> 4 files changed, 128 insertions(+), 19 deletions(-)
>>
>> Index: linux-3.5-rc6/include/linux/mm.h
>> ===================================================================
>> --- linux-3.5-rc6.orig/include/linux/mm.h 2012-07-18 18:01:28.000000000 +0900
>> +++ linux-3.5-rc6/include/linux/mm.h 2012-07-18 18:03:05.551168773 +0900
>> @@ -1588,6 +1588,8 @@ int vmemmap_populate(struct page *start_
>> void vmemmap_populate_print_last(void);
>> void register_page_bootmem_memmap(unsigned long section_nr, struct page *map,
>> unsigned long size);
>> +void vmemmap_kfree(struct page *memmpa, unsigned long nr_pages);
>> +void vmemmap_free_bootmem(struct page *memmpa, unsigned long nr_pages);
>>
>> enum mf_flags {
>> MF_COUNT_INCREASED = 1 << 0,
>> Index: linux-3.5-rc6/mm/sparse.c
>> ===================================================================
>> --- linux-3.5-rc6.orig/mm/sparse.c 2012-07-18 17:59:25.000000000 +0900
>> +++ linux-3.5-rc6/mm/sparse.c 2012-07-18 18:03:05.553168749 +0900
>> @@ -614,12 +614,13 @@ static inline struct page *kmalloc_secti
>> /* This will make the necessary allocations eventually. */
>> return sparse_mem_map_populate(pnum, nid);
>> }
>> -static void __kfree_section_memmap(struct page *memmap, unsigned long nr_pages)
>> +static void __kfree_section_memmap(struct page *page, unsigned long nr_pages)
>> {
>> - return; /* XXX: Not implemented yet */
>> + vmemmap_kfree(page, nr_pages);
>> }
>> static void free_map_bootmem(struct page *page, unsigned long nr_pages)
>> {
>> + vmemmap_free_bootmem(page, nr_pages);
>> }
>> #else
>> static struct page *__kmalloc_section_memmap(unsigned long nr_pages)
>> Index: linux-3.5-rc6/arch/x86/mm/init_64.c
>> ===================================================================
>> --- linux-3.5-rc6.orig/arch/x86/mm/init_64.c 2012-07-18 18:01:28.000000000 +0900
>> +++ linux-3.5-rc6/arch/x86/mm/init_64.c 2012-07-18 18:03:05.564168611 +0900
>> @@ -978,6 +978,127 @@ vmemmap_populate(struct page *start_page
>> return 0;
>> }
>>
>> +#define PAGE_INUSE 0xFD
>> +
>> +unsigned long find_and_clear_pte_page(unsigned long addr, unsigned long end,
>> + struct page **pp, int *page_size)
>> +{
>> + pgd_t *pgd;
>> + pud_t *pud;
>> + pmd_t *pmd;
>> + pte_t *pte;
>> + void *page_addr;
>> + unsigned long next;
>> +
>> + *pp = NULL;
>> +
>> + pgd = pgd_offset_k(addr);
>> + if (pgd_none(*pgd))
>> + return pgd_addr_end(addr, end);
>> +
>> + pud = pud_offset(pgd, addr);
>> + if (pud_none(*pud))
>> + return pud_addr_end(addr,end);
>> +
>> + if (!cpu_has_pse) {
>> + next = (addr + PAGE_SIZE) & PAGE_MASK;
>> + pmd = pmd_offset(pud, addr);
>> + if (pmd_none(*pmd))
>> + return next;
>> +
>> + pte = pte_offset_kernel(pmd, addr);
>> + if (pte_none(*pte))
>> + return next;
>> +
>> + *page_size = PAGE_SIZE;
>> + *pp = pte_page(*pte);
>> + } else {
>> + next = pmd_addr_end(addr, end);
>> +
>> + pmd = pmd_offset(pud, addr);
>> + if (pmd_none(*pmd))
>> + return next;
>> +
>> + *page_size = PMD_SIZE;
>> + *pp = pmd_page(*pmd);
>> + }
>> +
>> + /*
>> + * Removed page structs are filled with 0xFD.
>> + */
>> + memset((void *)addr, PAGE_INUSE, next - addr);
>> +
>> + page_addr = page_address(*pp);
>> +
>> + /*
>> + * Check the page is filled with 0xFD or not.
>> + * memchr_inv() returns the address. In this case, we cannot
>> + * clear PTE/PUD entry, since the page is used by other.
>> + * So we cannot also free the page.
>> + *
>> + * memchr_inv() returns NULL. In this case, we can clear
>> + * PTE/PUD entry, since the page is not used by other.
>> + * So we can also free the page.
>> + */
>> + if (memchr_inv(page_addr, PAGE_INUSE, *page_size)) {
>> + *pp = NULL;
>> + return next;
>> + }
>> +
>> + if (!cpu_has_pse)
>> + pte_clear(&init_mm, addr, pte);
>> + else
>> + pmd_clear(pmd);
>> +
>> + return next;
>> +}
>> +
>> +void vmemmap_kfree(struct page *memmap, unsigned long nr_pages)
>> +{
>> + unsigned long addr = (unsigned long)memmap;
>> + unsigned long end = (unsigned long)(memmap + nr_pages);
>> + unsigned long next;
>> + struct page *page;
>> + int page_size;
>> +
>> + for (; addr < end; addr = next) {
>> + page = NULL;
>> + page_size = 0;
>> + next = find_and_clear_pte_page(addr, end, &page, &page_size);
>> + if (!page)
>> + continue;
>> +
>> + free_pages((unsigned long)page_address(page),
>> + get_order(page_size));
>> + __flush_tlb_one((unsigned long)page_address(page));
>
> I think you want to free the memory to store struct page.
> So why you free page_address(page)?
I understand it now. page is for the memory to store struct page.
You clear page table's entry for the addr, not page_address(page).
And the entry for page_address(page) is still valid now.
So I think you want this:
__flush_tlb_one(addr);
Thanks
Wen Congyang
>
> Thanks
> Wen Congyang
>
>> + }
>> +
>> +}
>> +
>> +void vmemmap_free_bootmem(struct page *memmap, unsigned long nr_pages)
>> +{
>> + unsigned long addr = (unsigned long)memmap;
>> + unsigned long end = (unsigned long)(memmap + nr_pages);
>> + unsigned long next;
>> + struct page *page;
>> + int page_size;
>> + unsigned long magic;
>> +
>> + for (; addr < end; addr = next) {
>> + page = NULL;
>> + page_size = 0;
>> + next = find_and_clear_pte_page(addr, end, &page, &page_size);
>> + if (!page)
>> + continue;
>> +
>> + magic = (unsigned long) page->lru.next;
>> + if (magic == SECTION_INFO)
>> + put_page_bootmem(page);
>> + flush_tlb_kernel_range(addr, end);
>> + }
>> +
>> +}
>> +
>> void register_page_bootmem_memmap(unsigned long section_nr,
>> struct page *start_page, unsigned long size)
>> {
>> Index: linux-3.5-rc6/mm/memory_hotplug.c
>> ===================================================================
>> --- linux-3.5-rc6.orig/mm/memory_hotplug.c 2012-07-18 18:01:28.000000000 +0900
>> +++ linux-3.5-rc6/mm/memory_hotplug.c 2012-07-18 18:25:11.036597977 +0900
>> @@ -300,7 +300,6 @@ static int __meminit __add_section(int n
>> return register_new_memory(nid, __pfn_to_section(phys_start_pfn));
>> }
>>
>> -#ifdef CONFIG_SPARSEMEM_VMEMMAP
>> static int __remove_section(struct zone *zone, struct mem_section *ms)
>> {
>> int ret = -EINVAL;
>> @@ -309,29 +308,15 @@ static int __remove_section(struct zone
>> return ret;
>>
>> ret = unregister_memory_section(ms);
>> -
>> - return ret;
>> -}
>> -#else
>> -static int __remove_section(struct zone *zone, struct mem_section *ms)
>> -{
>> - unsigned long flags;
>> - struct pglist_data *pgdat = zone->zone_pgdat;
>> - int ret = -EINVAL;
>> -
>> - if (!valid_section(ms))
>> - return ret;
>> -
>> - ret = unregister_memory_section(ms);
>> if (ret)
>> return ret;
>>
>> pgdat_resize_lock(pgdat, &flags);
>> sparse_remove_one_section(zone, ms);
>> pgdat_resize_unlock(pgdat, &flags);
>> - return 0;
>> +
>> + return ret;
>> }
>> -#endif
>>
>> /*
>> * Reasonably generic function for adding memory. It is
>>
>> --
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>
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