Re: [PATCH 1 of 6] hotplug-memory: refactor online_pages to separate zone growth from page onlining

[Jeremy Fitzhardinge <jeremy@goop.org>]

Yasunori Goto wrote:
>> +/* Mark a set of pages as online */
>> +unsigned long mark_pages_onlined(unsigned long pfn, unsigned long nr_pages)
>> +{
>> +	struct zone *zone = page_zone(pfn_to_page(pfn));
>> +	unsigned long onlined_pages = 0;
>> +	int need_zonelists_rebuild = 0;
>>  
>>  	/*
>>  	 * If this zone is not populated, then it is not in zonelist.
>> @@ -240,10 +246,38 @@
>>  	vm_total_pages = nr_free_pagecache_pages();
>>  	writeback_set_ratelimit();
>>  
>> -	if (onlined_pages)
>> +	if (onlined_pages) {
>> +		struct memory_notify arg;
>> +
>> +		arg.start_pfn = pfn;  /* ? */
>> +		arg.nr_pages = onlined_pages;
>> +		arg.status_change_nid = -1;  /* ? */
>>     
>
> status_change_nid is to prepare data structures which are allocated on
> each NUMA node.
>   

OK.  I didn't really understand the intent this logic in the 
GOING_ONLINE notifier path:

	arg.status_change_nid = -1;

	nid = page_to_nid(pfn_to_page(pfn));
	if (node_present_pages(nid) == 0)
		arg.status_change_nid = nid;

and how that should relate to the ONLINE notifier.

> When memory less node gets new memory, and it changes status
> to normal memory, then status_change_nid must be set.
>
> SLUB uses it now.
>   

Only for GOING_ONLINE. 

    J