On 03/16/2012 10:40 AM, Peter Zijlstra wrote:
+/*
+ * Assumes symmetric NUMA -- that is, each node is of equal size.
+ */
+static void set_max_mem_load(unsigned long load)
+{
+ unsigned long old_load;
+
+ spin_lock(&max_mem_load.lock);
+ old_load = max_mem_load.load;
+ if (!old_load)
+ old_load = load;
+ max_mem_load.load = (old_load + load) >> 1;
+ spin_unlock(&max_mem_load.lock);
+}
The above in your patch kind of conflicts with this bit
from patch 6/26:
+ /*
+ * Migration allocates pages in the highest zone. If we cannot
+ * do so then migration (at least from node to node) is not
+ * possible.
+ */
+ if (vma->vm_file &&
+ gfp_zone(mapping_gfp_mask(vma->vm_file->f_mapping))
+ < policy_zone)
+ return 0;
Looking at how the memory load code is used, I wonder
if it would make sense to count "zone size - free - inactive
file" pages instead?
+ /*
+ * Avoid migrating ne's when we'll know we'll push our
+ * node over the memory limit.
+ */
+ if (max_mem_load &&
+ imb->mem_load + mem_moved + ne_mem > max_mem_load)
+ goto next;
+static void numa_balance(struct node_queue *this_nq)
+{
+ struct numa_imbalance imb;
+ int busiest;
+
+ busiest = find_busiest_node(this_nq->node, &imb);
+ if (busiest == -1)
+ return;
+
+ if (imb.cpu <= 0 && imb.mem <= 0)
+ return;
+
+ move_processes(nq_of(busiest), this_nq, &imb);
+}
You asked how and why Andrea's algorithm converges.
After looking at both patch sets for a while, and asking
for clarification, I think I can see how his code converges.
It is not yet clear to me how and why your code converges.
I see some dual bin packing (CPU & memory) heuristics, but
it is not at all clear to me how they interact, especially
when workloads are going active and idle on a regular basis.
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