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Message-ID: <4FFD14B0.9010606@jp.fujitsu.com>
Date: Wed, 11 Jul 2012 14:52:48 +0900
From: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To: Wen Congyang <wency@...fujitsu.com>
CC: <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
<linuxppc-dev@...ts.ozlabs.org>, <linux-acpi@...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>
Subject: Re: [RFC PATCH v3 11/13] memory-hotplug : free memmap of sparse-vmemmap
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@...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/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().
>
>> #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.
>> + }
>> + }
>> +}
>> +
>> +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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