Messages in this thread | | | Date | Tue, 4 Sep 2012 18:54:30 +0900 | From | Yasuaki Ishimatsu <> | Subject | Re: [RFC v8 PATCH 13/20] memory-hotplug: check page type in get_page_bootmem |
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Hi Wen,
2012/09/04 12:46, Wen Congyang wrote: > Hi, isimatu-san > > At 09/01/2012 05:30 AM, Andrew Morton Wrote: >> On Tue, 28 Aug 2012 18:00:20 +0800 >> wency@cn.fujitsu.com wrote: >> >>> From: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com> >>> >>> There is a possibility that get_page_bootmem() is called to the same page many >>> times. So when get_page_bootmem is called to the same page, the function only >>> increments page->_count. >> >> I really don't understand this explanation, even after having looked at >> the code. Can you please have another attempt at the changelog? > > What is the problem that you want to fix? The function get_page_bootmem() > may be called to the same page more than once, but I don't find any problem > about current implementation.
The patch is just optimization. The patch does not fix a problems. As you know, the function may be called many times for the same page. I think if a page is sets to page_type and Page Private flag and page->private, the page need not be set the same things again. So we check page_type when get_page_bootmem() is called. And if the page has been set to them, the page is only incremented page->_count.
Thanks, Yasuaki Ishimatsu
> > Thanks > Wen Congyang > >> >>> --- a/mm/memory_hotplug.c >>> +++ b/mm/memory_hotplug.c >>> @@ -95,10 +95,17 @@ static void release_memory_resource(struct resource *res) >>> static void get_page_bootmem(unsigned long info, struct page *page, >>> unsigned long type) >>> { >>> - page->lru.next = (struct list_head *) type; >>> - SetPagePrivate(page); >>> - set_page_private(page, info); >>> - atomic_inc(&page->_count); >>> + unsigned long page_type; >>> + >>> + page_type = (unsigned long) page->lru.next; >>> + if (page_type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE || >>> + page_type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE){ >>> + page->lru.next = (struct list_head *) type; >>> + SetPagePrivate(page); >>> + set_page_private(page, info); >>> + atomic_inc(&page->_count); >>> + } else >>> + atomic_inc(&page->_count); >>> } >> >> And a code comment which explains what is going on would be good. As >> is always the case ;) >> >> >
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