Hi Wen,
2012/07/11 15:25, Wen Congyang wrote:
> At 07/11/2012 01:52 PM, Yasuaki Ishimatsu Wrote:
>> 2012/07/11 14:06, Wen Congyang wrote:
>> Hi Wen,
>>
>>> At 07/09/2012 06:33 PM, Yasuaki Ishimatsu Wrote:
>>>> I don't think that all pages of virtual mapping in removed memory can be
>>>> freed, since page which type is MIX_SECTION_INFO is difficult to free.
>>>> So, the patch only frees page which type is SECTION_INFO at first.
>>>>
>>>> CC: David Rientjes <rientjes@xxxxxxxxxx>
>>>> CC: Jiang Liu <liuj97@xxxxxxxxx>
>>>> CC: Len Brown <len.brown@xxxxxxxxx>
>>>> CC: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
>>>> CC: Paul Mackerras <paulus@xxxxxxxxx>
>>>> CC: Christoph Lameter <cl@xxxxxxxxx>
>>>> Cc: Minchan Kim <minchan.kim@xxxxxxxxx>
>>>> CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>>>> CC: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
>>>> CC: Wen Congyang <wency@xxxxxxxxxxxxxx>
>>>> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
>>>>
>>>> ---
>>>> arch/x86/mm/init_64.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++
>>>> include/linux/mm.h | 2 +
>>>> mm/memory_hotplug.c | 5 ++
>>>> mm/sparse.c | 5 +-
>>>> 4 files changed, 101 insertions(+), 2 deletions(-)
>>>>
>>>> Index: linux-3.5-rc4/include/linux/mm.h
>>>> ===================================================================
>>>> --- linux-3.5-rc4.orig/include/linux/mm.h 2012-07-03 14:22:18.530011567 +0900
>>>> +++ linux-3.5-rc4/include/linux/mm.h 2012-07-03 14:22:20.999983872 +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-rc4/mm/sparse.c
>>>> ===================================================================
>>>> --- linux-3.5-rc4.orig/mm/sparse.c 2012-07-03 14:21:45.071429805 +0900
>>>> +++ linux-3.5-rc4/mm/sparse.c 2012-07-03 14:22:21.000983767 +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);
>>>
>>> Hmm, I think you try to free the memory allocated in kmalloc_section_memmap().
>>
>> Yes.
>>
>>>
>>>> }
>>>> static void free_map_bootmem(struct page *page, unsigned long nr_pages)
>>>> {
>>>> + vmemmap_free_bootmem(page, nr_pages);
>>>> }
>>>
>>> Hmm, which function is the memory you try to free allocated in?
>>
>> The function try to free memory allocated from bootmem. The memory has
>> been registered by get_page_bootmem(). So we can free the memory by
>> put_page_bootmem().
>
> OK, I will read these codes, and check it.
>
>>
>>>
>>>> #else
>>>> static struct page *__kmalloc_section_memmap(unsigned long nr_pages)
>>>> Index: linux-3.5-rc4/arch/x86/mm/init_64.c
>>>> ===================================================================
>>>> --- linux-3.5-rc4.orig/arch/x86/mm/init_64.c 2012-07-03 14:22:18.538011465 +0900
>>>> +++ linux-3.5-rc4/arch/x86/mm/init_64.c 2012-07-03 14:22:21.007983103 +0900
>>>> @@ -978,6 +978,97 @@ vmemmap_populate(struct page *start_page
>>>> return 0;
>>>> }
>>>>
>>>> +unsigned long find_and_clear_pte_page(unsigned long addr, unsigned long end,
>>>> + struct page **pp)
>>>> +{
>>>> + pgd_t *pgd;
>>>> + pud_t *pud;
>>>> + pmd_t *pmd;
>>>> + pte_t *pte;
>>>> + unsigned long next;
>>>> +
>>>> + *pp = NULL;
>>>> +
>>>> + pgd = pgd_offset_k(addr);
>>>> + if (pgd_none(*pgd))
>>>> + return (addr + PAGE_SIZE) & PAGE_MASK;
>>>
>>> Hmm, why not goto next pgd?
>>
>> Does it mean "return (addr + PGDIR_SIZE) & PGDIR_MASK"?
>>
>>>
>>>> +
>>>> + pud = pud_offset(pgd, addr);
>>>> + if (pud_none(*pud))
>>>> + return (addr + PAGE_SIZE) & PAGE_MASK;
>>>> +
>>>> + 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;
>>>> +
>>>> + *pp = pte_page(*pte);
>>>> + pte_clear(&init_mm, addr, pte);
>>>
>>> I think you should flush tlb here.
>>
>> Thanks, I'll update it.
>>
>>>
>>>> + } else {
>>>> + next = pmd_addr_end(addr, end);
>>>> +
>>>> + pmd = pmd_offset(pud, addr);
>>>> + if (pmd_none(*pmd))
>>>> + return next;
>>>> +
>>>> + *pp = pmd_page(*pmd);
>>>> + pmd_clear(pmd);
>>>> + }
>>>> +
>>>> + return next;
>>>> +}
>>>> +
>>>> +void __meminit
>>>> +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;
>>>> + unsigned int order;
>>>> + struct page *page;
>>>> +
>>>> + for (; addr < end; addr = next) {
>>>> + page = NULL;
>>>> + next = find_and_clear_pte_page(addr, end, &page);
>>>> + if (!page)
>>>> + continue;
>>>> +
>>>> + if (is_vmalloc_addr(page_address(page)))
>>>> + vfree(page_address(page));
>>>
>>> Hmm, the memory is allocated in vmemmap_alloc_block(), and the address
>>> can not be vmalloc address.
>>
>> Does it mean the if sentence is unnecessary?
>>
>>>
>>>> + else {
>>>> + order = next - addr;
>>>> + free_pages((unsigned long)page_address(page),
>>>> + get_order(order));
>>>
>>> OOPS. I think we cannot free pages here.
>>>
>>> sizeof(struct page) is less than PAGE_SIZE. We store more than one struct
>>> page in the same page. If you free it here while the other struct page
>>> is in use, it is very dangerous.
>>
>> The memory has page structures for hot-removed memory. So nobody is using
>> these pages, since the hot-removed memory has been offlined.
>
> The memory has page structures for hot-removed memory, but it may contain
> page structures for the other hot-added memory.
Yes. There may be such corner case. But when does the corner case appear?
When removed memory is not aligned to PMD_SIZE/PAGE_SIZE, does the corner
case appear? Do you know it?
Thank,
Yasuaki Ishimatsu
>
> IIUC, If we use sparse-vmemmap, all page structures is stored here.
>
> Thanks
> Wen Congyang
>
>>
>>>> + }
>>>> + }
>>>> +}
>>>> +
>>>> +void __meminit
>>>> +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;
>>>> + unsigned long magic;
>>>> +
>>>> + for (; addr < end; addr = next) {
>>>> + page = NULL;
>>>> + next = find_and_clear_pte_page(addr, end, &page);
>>>> + if (!page)
>>>> + continue;
>>>> +
>>>> + magic = (unsigned long) page->lru.next;
>>>> + if (magic == SECTION_INFO)
>>>> + put_page_bootmem(page);
>>>> + }
>>>> +}
>>>> +
>>>> void __meminit
>>>> register_page_bootmem_memmap(unsigned long section_nr, struct page *start_page,
>>>> unsigned long size)
>>>> Index: linux-3.5-rc4/mm/memory_hotplug.c
>>>> ===================================================================
>>>> --- linux-3.5-rc4.orig/mm/memory_hotplug.c 2012-07-03 14:22:18.522011667 +0900
>>>> +++ linux-3.5-rc4/mm/memory_hotplug.c 2012-07-03 14:22:21.012982694 +0900
>>>> @@ -303,6 +303,8 @@ static int __meminit __add_section(int n
>>>> #ifdef CONFIG_SPARSEMEM_VMEMMAP
>>>
>>> I think this line can be removed now.
>>
>> I'll update it.
>>
>> Thanks,
>> Yasuaki Ishimatsu
>>
>>>
>>> Thanks
>>> Wen Congyang
>>>
>>>> static int __remove_section(struct zone *zone, struct mem_section *ms)
>>>> {
>>>> + unsigned long flags;
>>>> + struct pglist_data *pgdat = zone->zone_pgdat;
>>>> int ret;
>>>>
>>>> if (!valid_section(ms))
>>>> @@ -310,6 +312,9 @@ static int __remove_section(struct zone
>>>>
>>>> ret = unregister_memory_section(ms);
>>>>
>>>> + pgdat_resize_lock(pgdat, &flags);
>>>> + sparse_remove_one_section(zone, ms);
>>>> + pgdat_resize_unlock(pgdat, &flags);
>>>> return ret;
>>>> }
>>>> #else
>>>>
>>>>
>>>
>>
>>
>>
>>
>
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