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Subject[PATCH 3/9] numa,sched: track from which nodes NUMA faults are triggered
Date
From: Rik van Riel <riel@redhat.com>

Track which nodes NUMA faults are triggered from, in other words
the CPUs on which the NUMA faults happened. This uses a similar
mechanism to what is used to track the memory involved in numa faults.

The next patches use this to build up a bitmap of which nodes a
workload is actively running on.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Chegu Vinod <chegu_vinod@hp.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
---
include/linux/sched.h | 10 ++++++++--
kernel/sched/fair.c | 30 +++++++++++++++++++++++-------
2 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index b8f8476..d14d9fe 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1492,6 +1492,14 @@ struct task_struct {
unsigned long *numa_faults_buffer_memory;

/*
+ * Track the nodes where faults are incurred. This is not very
+ * interesting on a per-task basis, but it help with smarter
+ * numa memory placement for groups of processes.
+ */
+ unsigned long *numa_faults_cpu;
+ unsigned long *numa_faults_buffer_cpu;
+
+ /*
* numa_faults_locality tracks if faults recorded during the last
* scan window were remote/local. The task scan period is adapted
* based on the locality of the faults with different weights
@@ -1594,8 +1602,6 @@ extern void task_numa_fault(int last_node, int node, int pages, int flags);
extern pid_t task_numa_group_id(struct task_struct *p);
extern void set_numabalancing_state(bool enabled);
extern void task_numa_free(struct task_struct *p);
-
-extern unsigned int sysctl_numa_balancing_migrate_deferred;
#else
static inline void task_numa_fault(int last_node, int node, int pages,
int flags)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6560145..b98ed61 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -886,6 +886,7 @@ struct numa_group {

struct rcu_head rcu;
unsigned long total_faults;
+ unsigned long *faults_cpu;
unsigned long faults[0];
};

@@ -1372,10 +1373,11 @@ static void task_numa_placement(struct task_struct *p)
int priv, i;

for (priv = 0; priv < 2; priv++) {
- long diff;
+ long diff, f_diff;

i = task_faults_idx(nid, priv);
diff = -p->numa_faults_memory[i];
+ f_diff = -p->numa_faults_cpu[i];

/* Decay existing window, copy faults since last scan */
p->numa_faults_memory[i] >>= 1;
@@ -1383,12 +1385,18 @@ static void task_numa_placement(struct task_struct *p)
fault_types[priv] += p->numa_faults_buffer_memory[i];
p->numa_faults_buffer_memory[i] = 0;

+ p->numa_faults_cpu[i] >>= 1;
+ p->numa_faults_cpu[i] += p->numa_faults_buffer_cpu[i];
+ p->numa_faults_buffer_cpu[i] = 0;
+
faults += p->numa_faults_memory[i];
diff += p->numa_faults_memory[i];
+ f_diff += p->numa_faults_cpu[i];
p->total_numa_faults += diff;
if (p->numa_group) {
/* safe because we can only change our own group */
p->numa_group->faults[i] += diff;
+ p->numa_group->faults_cpu[i] += f_diff;
p->numa_group->total_faults += diff;
group_faults += p->numa_group->faults[i];
}
@@ -1457,7 +1465,7 @@ static void task_numa_group(struct task_struct *p, int cpupid, int flags,

if (unlikely(!p->numa_group)) {
unsigned int size = sizeof(struct numa_group) +
- 2*nr_node_ids*sizeof(unsigned long);
+ 4*nr_node_ids*sizeof(unsigned long);

grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
if (!grp)
@@ -1467,8 +1475,10 @@ static void task_numa_group(struct task_struct *p, int cpupid, int flags,
spin_lock_init(&grp->lock);
INIT_LIST_HEAD(&grp->task_list);
grp->gid = p->pid;
+ /* Second half of the array tracks nids where faults happen */
+ grp->faults_cpu = grp->faults + 2 * nr_node_ids;

- for (i = 0; i < 2*nr_node_ids; i++)
+ for (i = 0; i < 4*nr_node_ids; i++)
grp->faults[i] = p->numa_faults_memory[i];

grp->total_faults = p->total_numa_faults;
@@ -1526,7 +1536,7 @@ static void task_numa_group(struct task_struct *p, int cpupid, int flags,

double_lock(&my_grp->lock, &grp->lock);

- for (i = 0; i < 2*nr_node_ids; i++) {
+ for (i = 0; i < 4*nr_node_ids; i++) {
my_grp->faults[i] -= p->numa_faults_memory[i];
grp->faults[i] += p->numa_faults_memory[i];
}
@@ -1558,7 +1568,7 @@ void task_numa_free(struct task_struct *p)

if (grp) {
spin_lock(&grp->lock);
- for (i = 0; i < 2*nr_node_ids; i++)
+ for (i = 0; i < 4*nr_node_ids; i++)
grp->faults[i] -= p->numa_faults_memory[i];
grp->total_faults -= p->total_numa_faults;

@@ -1571,6 +1581,8 @@ void task_numa_free(struct task_struct *p)

p->numa_faults_memory = NULL;
p->numa_faults_buffer_memory = NULL;
+ p->numa_faults_cpu= NULL;
+ p->numa_faults_buffer_cpu = NULL;
kfree(numa_faults);
}

@@ -1581,6 +1593,7 @@ void task_numa_fault(int last_cpupid, int node, int pages, int flags)
{
struct task_struct *p = current;
bool migrated = flags & TNF_MIGRATED;
+ int this_node = task_node(current);
int priv;

if (!numabalancing_enabled)
@@ -1596,7 +1609,7 @@ void task_numa_fault(int last_cpupid, int node, int pages, int flags)

/* Allocate buffer to track faults on a per-node basis */
if (unlikely(!p->numa_faults_memory)) {
- int size = sizeof(*p->numa_faults_memory) * 2 * nr_node_ids;
+ int size = sizeof(*p->numa_faults_memory) * 4 * nr_node_ids;

/* numa_faults and numa_faults_buffer share the allocation */
p->numa_faults_memory = kzalloc(size * 2, GFP_KERNEL|__GFP_NOWARN);
@@ -1604,7 +1617,9 @@ void task_numa_fault(int last_cpupid, int node, int pages, int flags)
return;

BUG_ON(p->numa_faults_buffer_memory);
- p->numa_faults_buffer_memory = p->numa_faults_memory + (2 * nr_node_ids);
+ p->numa_faults_cpu = p->numa_faults_memory + (2 * nr_node_ids);
+ p->numa_faults_buffer_memory = p->numa_faults_memory + (4 * nr_node_ids);
+ p->numa_faults_buffer_cpu = p->numa_faults_memory + (6 * nr_node_ids);
p->total_numa_faults = 0;
memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
}
@@ -1634,6 +1649,7 @@ void task_numa_fault(int last_cpupid, int node, int pages, int flags)
p->numa_pages_migrated += pages;

p->numa_faults_buffer_memory[task_faults_idx(node, priv)] += pages;
+ p->numa_faults_buffer_cpu[task_faults_idx(this_node, priv)] += pages;
p->numa_faults_locality[!!(flags & TNF_FAULT_LOCAL)] += pages;
}

--
1.8.4.2


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