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Message-ID: <50703DAA.20407@gmail.com>
Date: Sat, 06 Oct 2012 22:18:18 +0800
From: Ni zhan Chen <nizhan.chen@...il.com>
To: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
CC: x86@...nel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org, linux-acpi@...r.kernel.org,
linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
linux-ia64@...r.kernel.org, cmetcalf@...era.com,
sparclinux@...r.kernel.org, rientjes@...gle.com, liuj97@...il.com,
len.brown@...el.com, benh@...nel.crashing.org, paulus@...ba.org,
cl@...ux.com, minchan.kim@...il.com, akpm@...ux-foundation.org,
kosaki.motohiro@...fujitsu.com, Wen Congyang <wency@...fujitsu.com>
Subject: Re: [RFC v9 PATCH 16/21] memory-hotplug: free memmap of sparse-vmemmap
On 10/04/2012 02:26 PM, Yasuaki Ishimatsu wrote:
> Hi Chen,
>
> Sorry for late reply.
>
> 2012/10/02 13:21, Ni zhan Chen wrote:
>> On 09/05/2012 05:25 PM, wency@...fujitsu.com wrote:
>>> From: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
>>>
>>> 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.
>>>
>>> Note: vmemmap_kfree() and vmemmap_free_bootmem() are not
>>> implemented for ia64,
>>> ppc, s390, and sparc.
>>>
>>> CC: David Rientjes <rientjes@...gle.com>
>>> CC: Jiang Liu <liuj97@...il.com>
>>> CC: Len Brown <len.brown@...el.com>
>>> CC: Benjamin Herrenschmidt <benh@...nel.crashing.org>
>>> CC: Paul Mackerras <paulus@...ba.org>
>>> CC: Christoph Lameter <cl@...ux.com>
>>> Cc: Minchan Kim <minchan.kim@...il.com>
>>> CC: Andrew Morton <akpm@...ux-foundation.org>
>>> CC: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
>>> CC: Wen Congyang <wency@...fujitsu.com>
>>> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
>>> ---
>>> arch/ia64/mm/discontig.c | 8 +++
>>> arch/powerpc/mm/init_64.c | 8 +++
>>> arch/s390/mm/vmem.c | 8 +++
>>> arch/sparc/mm/init_64.c | 8 +++
>>> arch/x86/mm/init_64.c | 119
>>> +++++++++++++++++++++++++++++++++++++++++++++
>>> include/linux/mm.h | 2 +
>>> mm/memory_hotplug.c | 17 +------
>>> mm/sparse.c | 5 +-
>>> 8 files changed, 158 insertions(+), 17 deletions(-)
>>>
>>> diff --git a/arch/ia64/mm/discontig.c b/arch/ia64/mm/discontig.c
>>> index 33943db..0d23b69 100644
>>> --- a/arch/ia64/mm/discontig.c
>>> +++ b/arch/ia64/mm/discontig.c
>>> @@ -823,6 +823,14 @@ int __meminit vmemmap_populate(struct page
>>> *start_page,
>>> return vmemmap_populate_basepages(start_page, size, node);
>>> }
>>> +void vmemmap_kfree(struct page *memmap, unsigned long nr_pages)
>>> +{
>>> +}
>>> +
>>> +void vmemmap_free_bootmem(struct page *memmap, unsigned long nr_pages)
>>> +{
>>> +}
>>> +
>>> void register_page_bootmem_memmap(unsigned long section_nr,
>>> struct page *start_page, unsigned long size)
>>> {
>>> diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
>>> index 3690c44..835a2b3 100644
>>> --- a/arch/powerpc/mm/init_64.c
>>> +++ b/arch/powerpc/mm/init_64.c
>>> @@ -299,6 +299,14 @@ int __meminit vmemmap_populate(struct page
>>> *start_page,
>>> return 0;
>>> }
>>> +void vmemmap_kfree(struct page *memmap, unsigned long nr_pages)
>>> +{
>>> +}
>>> +
>>> +void vmemmap_free_bootmem(struct page *memmap, unsigned long nr_pages)
>>> +{
>>> +}
>>> +
>>> void register_page_bootmem_memmap(unsigned long section_nr,
>>> struct page *start_page, unsigned long size)
>>> {
>>> diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
>>> index eda55cd..4b42b0b 100644
>>> --- a/arch/s390/mm/vmem.c
>>> +++ b/arch/s390/mm/vmem.c
>>> @@ -227,6 +227,14 @@ out:
>>> return ret;
>>> }
>>> +void vmemmap_kfree(struct page *memmap, unsigned long nr_pages)
>>> +{
>>> +}
>>> +
>>> +void vmemmap_free_bootmem(struct page *memmap, unsigned long nr_pages)
>>> +{
>>> +}
>>> +
>>> void register_page_bootmem_memmap(unsigned long section_nr,
>>> struct page *start_page, unsigned long size)
>>> {
>>> diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
>>> index add1cc7..1384826 100644
>>> --- a/arch/sparc/mm/init_64.c
>>> +++ b/arch/sparc/mm/init_64.c
>>> @@ -2078,6 +2078,14 @@ void __meminit vmemmap_populate_print_last(void)
>>> }
>>> }
>>> +void vmemmap_kfree(struct page *memmap, unsigned long nr_pages)
>>> +{
>>> +}
>>> +
>>> +void vmemmap_free_bootmem(struct page *memmap, unsigned long nr_pages)
>>> +{
>>> +}
>>> +
>>> void register_page_bootmem_memmap(unsigned long section_nr,
>>> struct page *start_page, unsigned long size)
>>> {
>>> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
>>> index 0075592..4e8f8a4 100644
>>> --- a/arch/x86/mm/init_64.c
>>> +++ b/arch/x86/mm/init_64.c
>>> @@ -1138,6 +1138,125 @@ vmemmap_populate(struct page *start_page,
>>> unsigned long size, int node)
>>> 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;
>>> + }
>>> +
>>
>> Hi Yasuaki,
>>
>> why call memchr_inv check after memset, this time the page can always
>> be filled with 0xFD.
>
> The page is not always filled with 0xFD. find_and_clear_pte_page()
> is calld in each section. So the function fills the page
> section size/sizeof(page) byte with 0xFD one time. Thus if section
> size is
> small, the page is filled with 0xFD.
Hi Yasuaki,
But when section size will be small?
Regards,
Chen
>
> Thanks,
> Yasuaki Ishimatsu
>
>
>>> + 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(addr);
>>> + }
>>> +}
>>> +
>>> +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)
>>> {
>>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>>> index c607913..fb0d1fc 100644
>>> --- a/include/linux/mm.h
>>> +++ b/include/linux/mm.h
>>> @@ -1620,6 +1620,8 @@ int vmemmap_populate(struct page *start_page,
>>> unsigned long pages, int node);
>>> 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,
>>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>>> index 647a7f2..c54922c 100644
>>> --- a/mm/memory_hotplug.c
>>> +++ b/mm/memory_hotplug.c
>>> @@ -308,19 +308,6 @@ static int __meminit __add_section(int nid,
>>> struct zone *zone,
>>> 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;
>>> -
>>> - if (!valid_section(ms))
>>> - return ret;
>>> -
>>> - ret = unregister_memory_section(ms);
>>> -
>>> - return ret;
>>> -}
>>> -#else
>>> static int __remove_section(struct zone *zone, struct mem_section
>>> *ms)
>>> {
>>> unsigned long flags;
>>> @@ -337,9 +324,9 @@ static int __remove_section(struct zone *zone,
>>> struct mem_section *ms)
>>> 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
>>> diff --git a/mm/sparse.c b/mm/sparse.c
>>> index fac95f2..ab9d755 100644
>>> --- a/mm/sparse.c
>>> +++ b/mm/sparse.c
>>> @@ -613,12 +613,13 @@ static inline struct page
>>> *kmalloc_section_memmap(unsigned long pnum, int nid,
>>> /* 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)
>>
>
>
>
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