Re: [RFC PATCH 10/12] mm: add the buddy system interface

[Xishi Qiu <qiuxishi@huawei.com>]

On 2015/6/26 7:54, Kamezawa Hiroyuki wrote:

> On 2015/06/25 18:44, Xishi Qiu wrote:
>> On 2015/6/10 11:06, Kamezawa Hiroyuki wrote:
>>
>>> On 2015/06/09 19:04, Xishi Qiu wrote:
>>>> On 2015/6/9 15:12, Kamezawa Hiroyuki wrote:
>>>>
>>>>> On 2015/06/04 22:04, Xishi Qiu wrote:
>>>>>> Add the buddy system interface for address range mirroring feature.
>>>>>> Allocate mirrored pages in MIGRATE_MIRROR list. If there is no mirrored pages
>>>>>> left, use other types pages.
>>>>>>
>>>>>> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
>>>>>> ---
>>>>>>     mm/page_alloc.c | 40 +++++++++++++++++++++++++++++++++++++++-
>>>>>>     1 file changed, 39 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>>>>> index d4d2066..0fb55288 100644
>>>>>> --- a/mm/page_alloc.c
>>>>>> +++ b/mm/page_alloc.c
>>>>>> @@ -599,6 +599,26 @@ static inline bool is_mirror_pfn(unsigned long pfn)
>>>>>>
>>>>>>         return false;
>>>>>>     }
>>>>>> +
>>>>>> +static inline bool change_to_mirror(gfp_t gfp_flags, int high_zoneidx)
>>>>>> +{
>>>>>> +    /*
>>>>>> +     * Do not alloc mirrored memory below 4G, because 0-4G is
>>>>>> +     * all mirrored by default, and the list is always empty.
>>>>>> +     */
>>>>>> +    if (high_zoneidx < ZONE_NORMAL)
>>>>>> +        return false;
>>>>>> +
>>>>>> +    /* Alloc mirrored memory for only kernel */
>>>>>> +    if (gfp_flags & __GFP_MIRROR)
>>>>>> +        return true;
>>>>>
>>>>> GFP_KERNEL itself should imply mirror, I think.
>>>>>
>>>>
>>>> Hi Kame,
>>>>
>>>> How about like this: #define GFP_KERNEL (__GFP_WAIT | __GFP_IO | __GFP_FS | __GFP_MIRROR) ?
>>>>
>>>
>>> Hm.... it cannot cover GFP_ATOMIC at el.
>>>
>>> I guess, mirrored memory should be allocated if !__GFP_HIGHMEM or !__GFP_MOVABLE
>>
>>
>> Hi Kame,
>>
>> Can we distinguish allocations form user or kernel only by GFP flags?
>>
> 
> Allocation from user and file caches are now *always* done with __GFP_MOVABLE.
> 
> By this, pages will be allocated from MIGRATE_MOVABLE migration type.
> MOVABLE migration type means it's can
> be the target for page compaction or memory-hot-remove.
> 
> Thanks,
> -Kame
> 

So if we want all kernel memory allocated from mirror, how about change like this?
__alloc_pages_nodemask()
  gfpflags_to_migratetype()
    if (!(gfp_mask & __GFP_MOVABLE))
	return MIGRATE_MIRROR

Thanks,
Xishi Qiu

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