linux-kernel - Re: [RFC v2 PATCH 7/8] mm: add the buddy system interface

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Date:	Tue, 30 Jun 2015 11:01:06 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Xishi Qiu <qiuxishi@...wei.com>
CC:	"Luck, Tony" <tony.luck@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
	Hanjun Guo <guohanjun@...wei.com>,
	Xiexiuqi <xiexiuqi@...wei.com>, "leon@...n.nu" <leon@...n.nu>,
	"Hansen, Dave" <dave.hansen@...el.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Vlastimil Babka <vbabka@...e.cz>, Mel Gorman <mgorman@...e.de>,
	Linux MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC v2 PATCH 7/8] mm: add the buddy system interface

On 2015/06/30 10:31, Xishi Qiu wrote:
> On 2015/6/30 9:01, Kamezawa Hiroyuki wrote:
>
>> On 2015/06/30 8:11, Luck, Tony wrote:
>>>> @@ -814,7 +814,7 @@ int __init_memblock memblock_clear_hotplug(phys_addr_t base, phys_addr_t size)
>>>>     */
>>>>    int __init_memblock memblock_mark_mirror(phys_addr_t base, phys_addr_t size)
>>>>    {
>>>> -    system_has_some_mirror = true;
>>>> +    static_key_slow_inc(&system_has_mirror);
>>>>
>>>>        return memblock_setclr_flag(base, size, 1, MEMBLOCK_MIRROR);
>>>>    }
>>>
>>> This generates some WARN_ON noise when called from efi_find_mirror():
>>>
>>
>> It seems jump_label_init() is called after memory initialization. (init/main.c::start_kernel())
>> So, it may be difficut to use static_key function for our purpose because
>> kernel memory allocation may occur before jump_label is ready.
>>
>> Thanks,
>> -Kame
>>
>
> Hi Kame,
>
> How about like this? Use static bool in bootmem, and use jump label in buddy system.
> This means we use two variable to do it.
>

I think it can be done but it should be done in separated patch with enough comment/changelog.

Thanks,
-Kame



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