From: Jiang Liu <liuj97@gmail.com>
To: Sam Ravnborg <sam@ravnborg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
Jiang Liu <jiang.liu@huawei.com>,
Wen Congyang <wency@cn.fujitsu.com>, Mel Gorman <mgorman@suse.de>,
Minchan Kim <minchan@kernel.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Michal Hocko <mhocko@suse.cz>,
James Bottomley <James.Bottomley@HansenPartnership.com>,
Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>,
David Howells <dhowells@redhat.com>,
Mark Salter <msalter@redhat.com>,
Jianguo Wu <wujianguo@huawei.com>,
linux-mm@kvack.org, linux-arch@vger.kernel.org,
linux-kernel@vger.kernel.org, Tang Chen <tangchen@cn.fujitsu.com>,
Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Subject: Re: [PATCH v3, part4 38/39] mm/hotplug: prepare for removing num_physpages
Date: Sat, 30 Mar 2013 00:42:14 +0800 [thread overview]
Message-ID: <5155C466.9040406@gmail.com> (raw)
In-Reply-To: <20130329164014.GA6266@merkur.ravnborg.org>
On 03/30/2013 12:40 AM, Sam Ravnborg wrote:
> On Sat, Mar 30, 2013 at 12:30:14AM +0800, Jiang Liu wrote:
>> On 03/30/2013 12:17 AM, Sam Ravnborg wrote:
>>>>>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>>>>>> index 97454b3..9b1b494 100644
>>>>>> --- a/mm/memory_hotplug.c
>>>>>> +++ b/mm/memory_hotplug.c
>>>>>> @@ -751,10 +751,6 @@ EXPORT_SYMBOL_GPL(restore_online_page_callback);
>>>>>>
>>>>>> void __online_page_set_limits(struct page *page)
>>>>>> {
>>>>>> - unsigned long pfn = page_to_pfn(page);
>>>>>> -
>>>>>> - if (pfn >= num_physpages)
>>>>>> - num_physpages = pfn + 1;
>>>>>> }
>>>>>> EXPORT_SYMBOL_GPL(__online_page_set_limits);
>>>>>
>>>>> How can this be correct?
>>>>> With this change __online_page_set_limits() is now a nop.
>>>> Hi Sam,
>>>> We will eventually remove the global variable num_physpages in the last patch.
>>>> I kept the nop __online_page_set_limits() because I have a plan to use it to fix other
>>>> bugs in memory hotplug, otherwise it may be killed too.
>>>
>>> The xen ballon driver uses __online_page_set_limits for memory
>>> hotplug - so this will break this driver afaics.
>> Hi Sam,
>> I haven't gotten your point yet here.
>> Function __online_page_set_limits() was only used to update the global variable
>> num_physpages, and one of the goals of this patch set is to get rid of num_physpages.
>> So I think it won't break Xen balloon driver.
>> Please refer to the patch here, which eventually kills num_physpages.
>> http://marc.info/?l=linux-mm&m=136431387813309&w=2
>
> I assumed that num_physpages was used run-time to check for the
> available number of pages. And __online_page_set_limits() were used
> to reduced the number of online pages.
>
> But a quick grep did not reveal any such use.
>
> So it looks OK - thanks for the clarification.
Yeah, we have a patch to replace num_physpages with totalram_pages for runtime access,
please refer to:
http://marc.info/?l=linux-mm&m=136431351413052&w=2
>
> Sam
>
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next prev parent reply other threads:[~2013-03-29 16:42 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-26 15:54 [PATCH v3, part4 00/39] Simplify mem_init() implementations and kill num_physpages Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 01/39] vmlinux.lds: add comments for global variables and clean up useless declarations Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 02/39] avr32: normalize global variables exported by vmlinux.lds Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 03/39] c6x: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 04/39] h8300: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 05/39] score: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 06/39] tile: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 07/39] UML: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 08/39] mm: introduce helper function mem_init_print_info() to simplify mem_init() Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 09/39] mm: use totalram_pages instead of num_physpages at runtime Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 10/39] mm/alpha: prepare for removing num_physpages and simplify mem_init() Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 11/39] mm/ARM: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 12/39] mm/ARM64: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 13/39] mm/AVR32: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 14/39] mm/blackfin: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 15/39] mm/c6x: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 16/39] mm/cris: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 17/39] mm/frv: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 18/39] mm/h8300: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 19/39] mm/hexagon: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 20/39] mm/IA64: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 21/39] mm/m32r: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 22/39] mm/m68k: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 23/39] mm/microblaze: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 24/39] mm/MIPS: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 25/39] mm/mn10300: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 26/39] mm/openrisc: " Jiang Liu
2013-04-02 5:31 ` Jonas Bonn
2013-04-02 14:38 ` Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 27/39] mm/PARISC: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 28/39] mm/ppc: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 29/39] mm/s390: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 30/39] mm/score: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 31/39] mm/SH: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 32/39] mm/SPARC: " Jiang Liu
2013-03-29 16:17 ` Sam Ravnborg
2013-03-26 15:54 ` [PATCH v3, part4 33/39] mm/tile: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 34/39] mm/um: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 35/39] mm/unicore32: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 36/39] mm/x86: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 37/39] mm/xtensa: " Jiang Liu
2013-03-26 15:54 ` [PATCH v3, part4 38/39] mm/hotplug: prepare for removing num_physpages Jiang Liu
2013-03-29 11:18 ` Sam Ravnborg
2013-03-29 15:36 ` Jiang Liu
2013-03-29 16:17 ` Sam Ravnborg
2013-03-29 16:30 ` Jiang Liu
2013-03-29 16:40 ` Sam Ravnborg
2013-03-29 16:42 ` Jiang Liu [this message]
2013-03-26 15:54 ` [PATCH v3, part4 39/39] mm: kill global variable num_physpages Jiang Liu
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