Re: [PATCH 2 of 4] hotplug-memory: adding non-section-aligned memory is bad

[Jeremy Fitzhardinge <jeremy@goop.org>]

KAMEZAWA Hiroyuki wrote:
>> What would happen if I did online_pages(pfn, 1) on each page as I 
>> populate it?
>>
>>     
> I think (hope) it works well. But it seems no one tries to do that.

Well I had immediate problems because I try to use it under spinlock and 
it calls online_pages -> build_all_zonelists -> stop_machine_run.  I can 
easily rearrange to fix that, but it seems to me that stop_machine_run() 
is probably too expensive to call thousands of times (one for each page, 
rather than once per section).

I'm just looking at how I can refactor online_pages() into a function 
which does the general zone setup stuff, and one for actually onlining 
pages.  The function of online_pages() would remain unchanged for 
existing users, but I could call the pieces separately at the 
appropriate times.

    J