linux-kernel - Re: [RFC PATCH v3 04/35] mm: Initialize node memory regions during boot

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Date:	Tue, 3 Sep 2013 13:53:59 +0900
From:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
CC:	<akpm@...ux-foundation.org>, <mgorman@...e.de>,
	<hannes@...xchg.org>, <tony.luck@...el.com>,
	<matthew.garrett@...ula.com>, <dave@...1.net>, <riel@...hat.com>,
	<arjan@...ux.intel.com>, <srinivas.pandruvada@...ux.intel.com>,
	<willy@...ux.intel.com>, <kamezawa.hiroyu@...fujitsu.com>,
	<lenb@...nel.org>, <rjw@...k.pl>, <gargankita@...il.com>,
	<paulmck@...ux.vnet.ibm.com>, <svaidy@...ux.vnet.ibm.com>,
	<andi@...stfloor.org>, <santosh.shilimkar@...com>,
	<kosaki.motohiro@...il.com>, <linux-pm@...r.kernel.org>,
	<linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v3 04/35] mm: Initialize node memory regions during
 boot

(2013/09/03 2:43), Srivatsa S. Bhat wrote:
> On 09/02/2013 11:50 AM, Yasuaki Ishimatsu wrote:
>> (2013/08/30 22:15), Srivatsa S. Bhat wrote:
>>> Initialize the node's memory-regions structures with the information
>>> about
>>> the region-boundaries, at boot time.
>>>
>>> Based-on-patch-by: Ankita Garg <gargankita@...il.com>
>>> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
>>> ---
>>>
>>>    include/linux/mm.h |    4 ++++
>>>    mm/page_alloc.c    |   28 ++++++++++++++++++++++++++++
>>>    2 files changed, 32 insertions(+)
>>>
>>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>>> index f022460..18fdec4 100644
>>> --- a/include/linux/mm.h
>>> +++ b/include/linux/mm.h
>>> @@ -627,6 +627,10 @@ static inline pte_t maybe_mkwrite(pte_t pte,
>>> struct vm_area_struct *vma)
>>>    #define LAST_NID_MASK        ((1UL << LAST_NID_WIDTH) - 1)
>>>    #define ZONEID_MASK        ((1UL << ZONEID_SHIFT) - 1)
>>>
>>> +/* Hard-code memory region size to be 512 MB for now. */
>>> +#define MEM_REGION_SHIFT    (29 - PAGE_SHIFT)
>>> +#define MEM_REGION_SIZE        (1UL << MEM_REGION_SHIFT)
>>> +
>>>    static inline enum zone_type page_zonenum(const struct page *page)
>>>    {
>>>        return (page->flags >> ZONES_PGSHIFT) & ZONES_MASK;
>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>> index b86d7e3..bb2d5d4 100644
>>> --- a/mm/page_alloc.c
>>> +++ b/mm/page_alloc.c
>>> @@ -4809,6 +4809,33 @@ static void __init_refok
>>> alloc_node_mem_map(struct pglist_data *pgdat)
>>>    #endif /* CONFIG_FLAT_NODE_MEM_MAP */
>>>    }
>>>
>>> +static void __meminit init_node_memory_regions(struct pglist_data
>>> *pgdat)
>>> +{
>>> +    int nid = pgdat->node_id;
>>> +    unsigned long start_pfn = pgdat->node_start_pfn;
>>> +    unsigned long end_pfn = start_pfn + pgdat->node_spanned_pages;
>>> +    struct node_mem_region *region;
>>> +    unsigned long i, absent;
>>> +    int idx;
>>> +
>>> +    for (i = start_pfn, idx = 0; i < end_pfn;
>>> +                i += region->spanned_pages, idx++) {
>>> +
>>
>>> +        region = &pgdat->node_regions[idx];
>>
>> It seems that overflow easily occurs.
>> node_regions[] has 256 entries and MEM_REGION_SIZE is 512MiB. So if
>> the pgdat has more than 128 GiB, overflow will occur. Am I wrong?
>>
>
> No, you are right. It should be made dynamic to accommodate larger
> memory. I just used that value as a placeholder, since my focus was to
> demonstrate what algorithms and designs could be developed on top of
> this infrastructure, to help shape memory allocations. But certainly
> this needs to be modified to be flexible enough to work with any memory
> size. Thank you for your review!

Thank you for your explanation. I understood it.

Thanks,
Yasuaki Ishimatsu

>
> Regards,
> Srivatsa S. Bhat
>
>>
>>> +        region->pgdat = pgdat;
>>> +        region->start_pfn = i;
>>> +        region->spanned_pages = min(MEM_REGION_SIZE, end_pfn - i);
>>> +        region->end_pfn = region->start_pfn + region->spanned_pages;
>>> +
>>> +        absent = __absent_pages_in_range(nid, region->start_pfn,
>>> +                         region->end_pfn);
>>> +
>>> +        region->present_pages = region->spanned_pages - absent;
>>> +    }
>>> +
>>> +    pgdat->nr_node_regions = idx;
>>> +}
>>> +
>>>    void __paginginit free_area_init_node(int nid, unsigned long
>>> *zones_size,
>>>            unsigned long node_start_pfn, unsigned long *zholes_size)
>>>    {
>>> @@ -4837,6 +4864,7 @@ void __paginginit free_area_init_node(int nid,
>>> unsigned long *zones_size,
>>>
>>>        free_area_init_core(pgdat, start_pfn, end_pfn,
>>>                    zones_size, zholes_size);
>>> +    init_node_memory_regions(pgdat);
>>>    }
>>>
>>>    #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
>>>
>>
>>
>


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