linux-kernel - Re: [PATCH 9/9] numa,sched: define some magic numbers

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Message-ID: <20140121185826.26247d89@annuminas.surriel.com>
Date:	Tue, 21 Jan 2014 18:58:26 -0500
From:	Rik van Riel <riel@...hat.com>
To:	riel@...hat.com
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	peterz@...radead.org, mgorman@...e.de, mingo@...hat.com,
	chegu_vinod@...com
Subject: Re: [PATCH 9/9] numa,sched: define some magic numbers

On Tue, 21 Jan 2014 17:20:11 -0500
riel@...hat.com wrote:

> From: Rik van Riel <riel@...hat.com>
> 
> Cleanup suggested by Mel Gorman. Now the code contains some more
> hints on what statistics go where.
> 
> Suggested-by: Mel Gorman <mgorman@...e.de>
> Signed-off-by: Rik van Riel <riel@...hat.com>

... and patch fatigue hit, causing me to mess up this simple
patch with no functional changes (which is why I did not test
it yet).

Here is one that compiles.

---8<---

Subject: numa,sched: define some magic numbers

Cleanup suggested by Mel Gorman. Now the code contains some more
hints on what statistics go where.

Suggested-by: Mel Gorman <mgorman@...e.de>
Signed-off-by: Rik van Riel <riel@...hat.com>
---
 kernel/sched/fair.c | 34 +++++++++++++++++++++++++---------
 1 file changed, 25 insertions(+), 9 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 43ca8c4..6b9d27c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -896,6 +896,15 @@ struct numa_group {
 	unsigned long faults[0];
 };
 
+/* Shared or private faults. */
+#define NR_NUMA_HINT_FAULT_TYPES 2
+
+/* Memory and CPU locality */
+#define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
+
+/* Averaged statistics, and temporary buffers. */
+#define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
+
 pid_t task_numa_group_id(struct task_struct *p)
 {
 	return p->numa_group ? p->numa_group->gid : 0;
@@ -903,7 +912,7 @@ pid_t task_numa_group_id(struct task_struct *p)
 
 static inline int task_faults_idx(int nid, int priv)
 {
-	return 2 * nid + priv;
+	return NR_NUMA_HINT_FAULT_TYPES * nid + priv;
 }
 
 static inline unsigned long task_faults(struct task_struct *p, int nid)
@@ -1514,7 +1523,7 @@ static void task_numa_placement(struct task_struct *p)
 		unsigned long faults = 0, group_faults = 0;
 		int priv, i;
 
-		for (priv = 0; priv < 2; priv++) {
+		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
 			long diff, f_diff, f_weight;
 
 			i = task_faults_idx(nid, priv);
@@ -1625,11 +1634,12 @@ static void task_numa_group(struct task_struct *p, int cpupid, int flags,
 		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;
+		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
+						nr_node_ids;
 
 		node_set(task_node(current), grp->active_nodes);
 
-		for (i = 0; i < 4*nr_node_ids; i++)
+		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
 			grp->faults[i] = p->numa_faults_memory[i];
 
 		grp->total_faults = p->total_numa_faults;
@@ -1687,7 +1697,7 @@ static void task_numa_group(struct task_struct *p, int cpupid, int flags,
 
 	double_lock(&my_grp->lock, &grp->lock);
 
-	for (i = 0; i < 4*nr_node_ids; i++) {
+	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
 		my_grp->faults[i] -= p->numa_faults_memory[i];
 		grp->faults[i] += p->numa_faults_memory[i];
 	}
@@ -1726,7 +1736,7 @@ void task_numa_free(struct task_struct *p)
 
 	if (grp) {
 		spin_lock(&grp->lock);
-		for (i = 0; i < 4*nr_node_ids; i++)
+		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
 			grp->faults[i] -= p->numa_faults_memory[i];
 		grp->total_faults -= p->total_numa_faults;
 
@@ -1767,14 +1777,20 @@ void task_numa_fault(int last_cpupid, int mem_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) * 4 * nr_node_ids;
+		int size = sizeof(*p->numa_faults_memory) *
+			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
 
-		/* numa_faults and numa_faults_buffer share the allocation */
-		p->numa_faults_memory = kzalloc(size * 2, GFP_KERNEL|__GFP_NOWARN);
+		p->numa_faults_memory = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
 		if (!p->numa_faults_memory)
 			return;
 
 		BUG_ON(p->numa_faults_buffer_memory);
+		/*
+		 * The averaged statistics, shared & private, memory & cpu,
+		 * occupy the first half of the array. The second half of the
+		 * array is for current counters, which are averaged into the
+		 * first set by task_numa_placement.
+		 */
 		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);
--
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