Re: [Approach #2] [RFC][PATCH] Remove cgroup member from struct page

[Balbir Singh <balbir@linux.vnet.ibm.com>]

Dave Hansen wrote:
> On Tue, 2008-09-09 at 18:20 -0700, Balbir Singh wrote:
>> +       start = pgdat->node_start_pfn;
>> +       end = pgdat->node_start_pfn + pgdat->node_spanned_pages;
>> +       size = (end - start) * sizeof(struct page_cgroup);
>> +       printk("Allocating %lu bytes for node %d\n", size, n);
>> +       pcg_map[n] = alloc_bootmem_node(pgdat, size);
>> +       /*
>> +        * We can do smoother recovery
>> +        */
>> +       BUG_ON(!pcg_map[n]);
>> +       return 0;
>>  }
> 
> This will really suck for sparse memory machines.  Imagine a machine
> with 1GB of memory at 0x0 and another 1GB of memory at 1TB up in the
> address space.
> 

I would hate to re-implement the entire sparsemem code :(
Kame did suggest making the memory controller depend on sparsemem (to hook in
from there for allocations)

> You also need to consider how it works with memory hotplug and how
> you're going to grow it at runtime.
> 

Yes, true. This is not the final version, a very very early version that I
posted for initial comments.

> Oh, and doesn't alloc_bootmem() panic() if it fails internally anyway?
> 
> I need to look at your other approach. :)

We'll need some slab_is_available() sort of checks that sparse.c uses and also
deal with memory hotplug add and remove.

-- 
	Balbir