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

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Date:	Thu, 25 Jun 2015 17:44:53 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.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 2015/6/10 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?

Thanks,
Xishi Qiu

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