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

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Date:	Wed, 10 Jun 2015 12:06:17 +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 2015/06/09 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

thanks,
-Kame

Thanks,
-Kame



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