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

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Message-ID: <558C94BB.1060304@jp.fujitsu.com>
Date:	Fri, 26 Jun 2015 08:54:35 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Xishi Qiu <qiuxishi@...wei.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>, nao.horiguchi@...il.com,
	Yinghai Lu <yinghai@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>, mingo@...e.hu,
	Xiexiuqi <xiexiuqi@...wei.com>,
	Hanjun Guo <guohanjun@...wei.com>,
	"Luck, Tony" <tony.luck@...el.com>, Linux MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 10/12] mm: add the buddy system interface

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@...wei.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







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