Re: [PATCH v6][RFC] Fix hugetlb pool allocation with empty nodes

[Nishanth Aravamudan <nacc@us.ibm.com>]

On 11.06.2007 [20:44:07 -0700], William Lee Irwin III wrote:
> On 11.06.2007 [16:17:47 -0700], Christoph Lameter wrote:
> >> nid == 1 means local node? Or why do we check for nid < 0?
> >> 	if (nid == 1)
> >> 		 nid = numa_node_id();
> >> ?
> 
> On Mon, Jun 11, 2007 at 05:15:42PM -0700, Nishanth Aravamudan wrote:
> > No, nid is a static variable. So we initialize it to -1 to catch the
> > first time we go through the loop.
> > IIRC, we can't just set it to first_node(node_populated_map), because
> > it's a non-constant or something?
> 
> I wrote that, so I figure I should chime in. The static variable can
> be killed off outright.
> 
> Initially filling the pool doesn't need the static affair. Refilling
> the pool from the page allocator can refill the node with the least
> memory first, and choose randomly otherwise. Using default mpolicies
> or defaulting to node-local memory instead of round-robin allocation
> will likely do for callers into the allocator.
> 
> It depends a bit on what SGI's app that originally wanted striping of
> hugetlb does.
> 
> Also, if one has such a large number of nodes that exhaustive search
> for the node with the least memory would be prohibitive, esp. when in
> a loop, it's always possible to keep node ID's in an array
> heap-ordered by the number of pages in the node's segment of the pool.
> In such a manner the inner loop's search is limited to
> O(lg(nr_online_nodes())).

Well, (presuming I understood everything you wrote :), don't we need the
static 'affair' to guarantee the initial allocations are approximately
round-robin? Or, if we aren't going to make that guarantee, than we
should only change that once my sysfs allocator (or its equivalent) is
available?

Just trying to get a handle on what you're suggesting without any
historical context.

Thanks,
Nish

-- 
Nishanth Aravamudan <nacc@us.ibm.com>
IBM Linux Technology Center

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