scx: Replace /sys/kernel/debug/sched/ext with tools/sched_ext/scx_sho…

…w_state.py

Now that the state is visible through /sys/kernel/sched_ext,
/sys/kernel/debug/sched/ext isn't needed to determine the current state of
scx. However, /sys/kernel/sched_ext shows only a subset of information that
was available in the debug interface and it can be useful to have access to
the rest for debugging. Remove /sys/kernel/debug/sched/ext and add the drgn
script, tools/sched_ext/scx_show_state.py, which shows the same information.

Signed-off-by: Tejun Heo <[email protected]>

Documentation/scheduler/sched-ext.rst

@@ -60,9 +60,25 @@ The current status of the BPF scheduler can be determined as follows:
     # cat /sys/kernel/sched_ext/root/ops
     simple
 
+``tools/sched_ext/scx_show_state.py`` is a drgn script which shows more
+detailed information:
+
+.. code-block:: none
+
+    # tools/sched_ext/scx_show_state.py
+    ops           : simple
+    enabled       : 1
+    switching_all : 1
+    switched_all  : 1
+    enable_state  : enabled (2)
+    bypass_depth  : 0
+    nr_rejected   : 0
+
 If ``CONFIG_SCHED_DEBUG`` is set, whether a given task is on sched_ext can
 be determined as follows:
 
+.. code-block:: none
+
     # grep ext /proc/self/sched
     ext.enabled                                  :                    1
 

kernel/sched/debug.c

@@ -374,9 +374,6 @@ static __init int sched_init_debug(void)
 
 	debugfs_create_file("debug", 0444, debugfs_sched, NULL, &sched_debug_fops);
 
-#ifdef CONFIG_SCHED_CLASS_EXT
-	debugfs_create_file("ext", 0444, debugfs_sched, NULL, &sched_ext_fops);
-#endif
 	return 0;
 }
 late_initcall(sched_init_debug);

kernel/sched/ext.c

@@ -3724,37 +3724,6 @@ static int scx_ops_enable(struct sched_ext_ops *ops)
 	return ret;
 }
 
-#ifdef CONFIG_SCHED_DEBUG
-static int scx_debug_show(struct seq_file *m, void *v)
-{
-	mutex_lock(&scx_ops_enable_mutex);
-	seq_printf(m, "%-30s: %s\n", "ops", scx_ops.name);
-	seq_printf(m, "%-30s: %ld\n", "enabled", scx_enabled());
-	seq_printf(m, "%-30s: %d\n", "switching_all",
-		   READ_ONCE(scx_switching_all));
-	seq_printf(m, "%-30s: %ld\n", "switched_all", scx_switched_all());
-	seq_printf(m, "%-30s: %s\n", "enable_state",
-		   scx_ops_enable_state_str[scx_ops_enable_state()]);
-	seq_printf(m, "%-30s: %d\n", "bypassing", scx_ops_bypassing());
-	seq_printf(m, "%-30s: %lu\n", "nr_rejected",
-		   atomic_long_read(&scx_nr_rejected));
-	mutex_unlock(&scx_ops_enable_mutex);
-	return 0;
-}
-
-static int scx_debug_open(struct inode *inode, struct file *file)
-{
-	return single_open(file, scx_debug_show, NULL);
-}
-
-const struct file_operations sched_ext_fops = {
-	.open		= scx_debug_open,
-	.read		= seq_read,
-	.llseek		= seq_lseek,
-	.release	= single_release,
-};
-#endif
-
 
 /********************************************************************************
  * bpf_struct_ops plumbing.

kernel/sched/ext.h

@@ -103,7 +103,6 @@ void sched_enq_and_set_task(struct sched_enq_and_set_ctx *ctx);
 
 extern const struct sched_class ext_sched_class;
 extern const struct bpf_verifier_ops bpf_sched_ext_verifier_ops;
-extern const struct file_operations sched_ext_fops;
 extern unsigned long scx_watchdog_timeout;
 extern unsigned long scx_watchdog_timestamp;
 

tools/sched_ext/scx_show_state.py

@@ -0,0 +1,39 @@
+#!/usr/bin/env drgn
+#
+# Copyright (C) 2024 Tejun Heo <[email protected]>
+# Copyright (C) 2024 Meta Platforms, Inc. and affiliates.
+
+desc = """
+This is a drgn script to show the current sched_ext state.
+For more info on drgn, visit https://github.com/osandov/drgn.
+"""
+
+import drgn
+import sys
+
+def err(s):
+    print(s, file=sys.stderr, flush=True)
+    sys.exit(1)
+
+def read_int(name):
+    return int(prog[name].value_())
+
+def read_atomic(name):
+    return prog[name].counter.value_()
+
+def read_static_key(name):
+    return prog[name].key.enabled.counter.value_()
+
+def ops_state_str(state):
+    return prog['scx_ops_enable_state_str'][state].string_().decode()
+
+ops = prog['scx_ops']
+enable_state = read_atomic("scx_ops_enable_state_var")
+
+print(f'ops           : {ops.name.string_().decode()}')
+print(f'enabled       : {read_static_key("__scx_ops_enabled")}')
+print(f'switching_all : {read_int("scx_switching_all")}')
+print(f'switched_all  : {read_static_key("__scx_switched_all")}')
+print(f'enable_state  : {ops_state_str(enable_state)} ({enable_state})')
+print(f'bypass_depth  : {read_atomic("scx_ops_bypass_depth")}')
+print(f'nr_rejected   : {read_atomic("scx_nr_rejected")}')