sched/cache: Allow the user space to turn on and off cache aware scheduling

Provide a debugfs directory llc_balancing, and a knob named
"enabled" under it to allow the user to turn off and on the
cache aware scheduling at runtime.

Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/0aa56f7fc48db2f8f700cd1aa34dedd0ec88351b.1775065312.git.tim.c.chen@linux.intel.com

1 files changed, 47 insertions, 1 deletions

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 74c1617cf652..2eae67cd2ba2 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -210,6 +210,46 @@ static const struct file_operations sched_scaling_fops = {
 	.release	= single_release,
 };
 
+#ifdef CONFIG_SCHED_CACHE
+static ssize_t
+sched_cache_enable_write(struct file *filp, const char __user *ubuf,
+			 size_t cnt, loff_t *ppos)
+{
+	bool val;
+	int ret;
+
+	ret = kstrtobool_from_user(ubuf, cnt, &val);
+	if (ret)
+		return ret;
+
+	sysctl_sched_cache_user = val;
+
+	sched_cache_active_set_unlocked();
+
+	return cnt;
+}
+
+static int sched_cache_enable_show(struct seq_file *m, void *v)
+{
+	seq_printf(m, "%d\n", sysctl_sched_cache_user);
+	return 0;
+}
+
+static int sched_cache_enable_open(struct inode *inode,
+				   struct file *filp)
+{
+	return single_open(filp, sched_cache_enable_show, NULL);
+}
+
+static const struct file_operations sched_cache_enable_fops = {
+	.open           = sched_cache_enable_open,
+	.write          = sched_cache_enable_write,
+	.read           = seq_read,
+	.llseek         = seq_lseek,
+	.release        = single_release,
+};
+#endif
+
 #ifdef CONFIG_PREEMPT_DYNAMIC
 
 static ssize_t sched_dynamic_write(struct file *filp, const char __user *ubuf,
@@ -593,7 +633,7 @@ static void debugfs_ext_server_init(void)
 
 static __init int sched_init_debug(void)
 {
-	struct dentry __maybe_unused *numa;
+	struct dentry __maybe_unused *numa, *llc;
 
 	debugfs_sched = debugfs_create_dir("sched", NULL);
 
@@ -626,6 +666,12 @@ static __init int sched_init_debug(void)
 	debugfs_create_u32("hot_threshold_ms", 0644, numa, &sysctl_numa_balancing_hot_threshold);
 #endif /* CONFIG_NUMA_BALANCING */
 
+#ifdef CONFIG_SCHED_CACHE
+	llc = debugfs_create_dir("llc_balancing", debugfs_sched);
+	debugfs_create_file("enabled", 0644, llc, NULL,
+			    &sched_cache_enable_fops);
+#endif
+
 	debugfs_create_file("debug", 0444, debugfs_sched, NULL, &sched_debug_fops);
 
 	debugfs_fair_server_init();