From 343d4ead3b12992f494134114cf50e4f37c656c5 Mon Sep 17 00:00:00 2001
From: "Bjoern B. Brandenburg" <bbb@cs.unc.edu>
Date: Thu, 27 Jan 2011 16:23:46 -0500
Subject: Litmus core: add generic clustering support

Inspired by the existing C-EDF code, this generic version will build
clusters of CPUs based on a given cache level.
---
 litmus/clustered.c | 111 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 111 insertions(+)
 create mode 100644 litmus/clustered.c

(limited to 'litmus/clustered.c')

diff --git a/litmus/clustered.c b/litmus/clustered.c
new file mode 100644
index 000000000000..04450a8ad4fe
--- /dev/null
+++ b/litmus/clustered.c
@@ -0,0 +1,111 @@
+#include <linux/gfp.h>
+#include <linux/cpumask.h>
+#include <linux/list.h>
+
+#include <litmus/clustered.h>
+
+#ifndef CONFIG_X86
+/* fake get_shared_cpu_map() on non-x86 architectures */
+
+int get_shared_cpu_map(cpumask_var_t mask, unsigned int cpu, int index)
+{
+	if (index != 1)
+		return 1;
+	else {
+		/* Fake L1: CPU is all by itself. */
+		cpumask_clear(mask);
+		cpumask_set_cpu(cpu, mask);
+		return 0;
+	}
+}
+
+#endif
+
+int get_cluster_size(enum cache_level level)
+{
+	cpumask_var_t mask;
+	int ok;
+	int num_cpus;
+
+	if (level == GLOBAL_CLUSTER)
+		return num_online_cpus();
+	else {
+		if (!zalloc_cpumask_var(&mask, GFP_ATOMIC))
+			return -ENOMEM;
+		/* assumes CPU 0 is representative of all CPUs */
+		ok = get_shared_cpu_map(mask, 0, level);
+		/* ok == 0 means we got the map; otherwise it's an invalid cache level */
+		if (ok == 0)
+			num_cpus = cpumask_weight(mask);
+		free_cpumask_var(mask);
+
+		if (ok == 0)
+			return num_cpus;
+		else
+			return -EINVAL;
+	}
+}
+
+int assign_cpus_to_clusters(enum cache_level level,
+			    struct scheduling_cluster* clusters[],
+			    unsigned int num_clusters,
+			    struct cluster_cpu* cpus[],
+			    unsigned int num_cpus)
+{
+	cpumask_var_t mask;
+	unsigned int i, free_cluster = 0, low_cpu;
+	int err = 0;
+
+	if (!zalloc_cpumask_var(&mask, GFP_ATOMIC))
+		return -ENOMEM;
+
+	/* clear cluster pointers */
+	for (i = 0; i < num_cpus; i++) {
+		cpus[i]->id      = i;
+		cpus[i]->cluster = NULL;
+	}
+
+	/* initialize clusters */
+	for (i = 0; i < num_clusters; i++) {
+		clusters[i]->id = i;
+		INIT_LIST_HEAD(&clusters[i]->cpus);
+	}
+
+	/* Assign each CPU. Two assumtions are made:
+	 * 1) The index of a cpu in cpus corresponds to its processor id (i.e., the index in a cpu mask).
+	 * 2) All cpus that belong to some cluster are online.
+	 */
+	for_each_online_cpu(i) {
+		/* get lowest-id CPU in cluster */
+		if (level != GLOBAL_CLUSTER) {
+			err = get_shared_cpu_map(mask, cpus[i]->id, level);
+			if (err != 0) {
+				/* ugh... wrong cache level? Either caller screwed up
+				 * or the CPU topology is weird. */
+				printk(KERN_ERR "Could not set up clusters for L%d sharing (max: L%d).\n",
+				       level, err);
+				err = -EINVAL;
+				goto out;
+			}
+			low_cpu = cpumask_first(mask);
+		} else
+			low_cpu = 0;
+		if (low_cpu == i) {
+			/* caller must provide an appropriate number of clusters */
+			BUG_ON(free_cluster >= num_clusters);
+
+			/* create new cluster */
+			cpus[i]->cluster = clusters[free_cluster++];
+		} else {
+			/* low_cpu points to the right cluster
+			 * Assumption: low_cpu is actually online and was processed earlier. */
+			cpus[i]->cluster = cpus[low_cpu]->cluster;
+		}
+		/* enqueue in cpus list */
+		list_add(&cpus[i]->cluster_list, &cpus[i]->cluster->cpus);
+		printk(KERN_INFO "Assigning CPU%u to cluster %u\n.", i, cpus[i]->cluster->id);
+	}
+out:
+	free_cpumask_var(mask);
+	return err;
+}
-- 
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