On 01/20/2014 11:31 AM, Peter Zijlstra wrote:
> On Fri, Jan 17, 2014 at 04:12:05PM -0500, riel@xxxxxxxxxx wrote:
>> /*
>> + * Iterate over the nodes from which NUMA hinting faults were triggered, in
>> + * other words where the CPUs that incurred NUMA hinting faults are. The
>> + * bitmask is used to limit NUMA page migrations, and spread out memory
>> + * between the actively used nodes. To prevent flip-flopping, and excessive
>> + * page migrations, nodes are added when they cause over 40% of the maximum
>> + * number of faults, but only removed when they drop below 20%.
>> + */
>> +static void update_numa_active_node_mask(struct task_struct *p)
>> +{
>> + unsigned long faults, max_faults = 0;
>> + struct numa_group *numa_group = p->numa_group;
>> + int nid;
>> +
>> + for_each_online_node(nid) {
>> + faults = numa_group->faults_from[task_faults_idx(nid, 0)] +
>> + numa_group->faults_from[task_faults_idx(nid, 1)];
>> + if (faults > max_faults)
>> + max_faults = faults;
>> + }
>> +
>> + for_each_online_node(nid) {
>> + faults = numa_group->faults_from[task_faults_idx(nid, 0)] +
>> + numa_group->faults_from[task_faults_idx(nid, 1)];
>> + if (!node_isset(nid, numa_group->active_nodes)) {
>> + if (faults > max_faults * 4 / 10)
>> + node_set(nid, numa_group->active_nodes);
>> + } else if (faults < max_faults * 2 / 10)
>> + node_clear(nid, numa_group->active_nodes);
>> + }
>> +}
>
> Why not use 6/16 and 3/16 resp.? That avoids an actual division.
OK, will do.
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