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sched/numa: Build per numa_group active node mask from numa_faults_cpu statistics 

The numa_faults_cpu statistics are used to maintain an active_nodes nodemask
per numa_group. This allows us to be smarter about when to do numa migrations.

Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Chegu Vinod <chegu_vinod@hp.com>
Link: http://lkml.kernel.org/r/1390860228-21539-5-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Rik van Riel 2014-01-27 17:03:43 -05:00 committed by Ingo Molnar
parent 50ec8a401f
commit 20e07dea28
1 changed files with 42 additions and 0 deletions
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42
kernel/sched/fair.c
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@ -885,6 +885,7 @@ struct numa_group {
struct list_head task_list;
struct rcu_head rcu;
nodemask_t active_nodes;
unsigned long total_faults;
unsigned long *faults_cpu;
unsigned long faults[0];
@ -918,6 +919,12 @@ static inline unsigned long group_faults(struct task_struct *p, int nid)
p->numa_group->faults[task_faults_idx(nid, 1)];
}
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
return group->faults_cpu[task_faults_idx(nid, 0)] +
group->faults_cpu[task_faults_idx(nid, 1)];
}
/*
* These return the fraction of accesses done by a particular task, or
* task group, on a particular numa node. The group weight is given a
@ -1270,6 +1277,38 @@ static void numa_migrate_preferred(struct task_struct *p)
task_numa_migrate(p);
}
/*
* Find the nodes on which the workload is actively running. We do this by
* tracking the nodes from which NUMA hinting faults are triggered. This can
* be different from the set of nodes where the workload's memory is currently
* located.
*
* The bitmask is used to make smarter decisions on when to do NUMA page
* migrations, To prevent flip-flopping, and excessive page migrations, nodes
* are added when they cause over 6/16 of the maximum number of faults, but
* only removed when they drop below 3/16.
*/
static void update_numa_active_node_mask(struct numa_group *numa_group)
{
unsigned long faults, max_faults = 0;
int nid;
for_each_online_node(nid) {
faults = group_faults_cpu(numa_group, nid);
if (faults > max_faults)
max_faults = faults;
}
for_each_online_node(nid) {
faults = group_faults_cpu(numa_group, nid);
if (!node_isset(nid, numa_group->active_nodes)) {
if (faults > max_faults * 6 / 16)
node_set(nid, numa_group->active_nodes);
} else if (faults < max_faults * 3 / 16)
node_clear(nid, numa_group->active_nodes);
}
}
/*
* When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
* increments. The more local the fault statistics are, the higher the scan
@ -1412,6 +1451,7 @@ static void task_numa_placement(struct task_struct *p)
update_task_scan_period(p, fault_types[0], fault_types[1]);
if (p->numa_group) {
update_numa_active_node_mask(p->numa_group);
/*
* If the preferred task and group nids are different,
* iterate over the nodes again to find the best place.
@ -1474,6 +1514,8 @@ static void task_numa_group(struct task_struct *p, int cpupid, int flags,
/* Second half of the array tracks nids where faults happen */
grp->faults_cpu = grp->faults + 2 * nr_node_ids;
node_set(task_node(current), grp->active_nodes);
for (i = 0; i < 4*nr_node_ids; i++)
grp->faults[i] = p->numa_faults_memory[i];