[RFC][PATCH] dynamically enable readprofile at runtime

[Dave Hansen <dave@linux.vnet.ibm.com>]

Way too often, I have a machine that exhibits some kind of crappy
behavior.  The CPU looks wedged in the kernel or it is spending
way too much system time and I wonder what is responsible.

I try to run readprofile.  But, of course, Ubuntu doesn't enable
it by default.  Dang!

The reason we boot-time enable it is that it takes a big bufffer
that we generally can only bootmem alloc.  But, does it hurt to
at least try and runtime-alloc it?

To use:
echo 2 > /sys/kernel/profile

Then run readprofile like normal.


Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
---

 linux-2.6.git-dave/kernel/ksysfs.c  |   29 +++++++++++++++++++++++++++++
 linux-2.6.git-dave/kernel/profile.c |   33 ++++++++++++++++++++++++---------
 2 files changed, 53 insertions(+), 9 deletions(-)

diff -puN kernel/ksysfs.c~dynamic-readprofile kernel/ksysfs.c
--- linux-2.6.git/kernel/ksysfs.c~dynamic-readprofile	2008-08-29 13:15:52.000000000 -0700
+++ linux-2.6.git-dave/kernel/ksysfs.c	2008-08-29 13:19:03.000000000 -0700
@@ -14,6 +14,7 @@
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/kexec.h>
+#include <linux/profile.h>
 #include <linux/sched.h>
 
 #define KERNEL_ATTR_RO(_name) \
@@ -53,6 +54,31 @@ static ssize_t uevent_helper_store(struc
 KERNEL_ATTR_RW(uevent_helper);
 #endif
 
+#ifdef CONFIG_PROFILING
+/* uevent helper program, used during early boo */
+static ssize_t profiling_show(struct kobject *kobj,
+				  struct kobj_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d\n", prof_on);
+}
+static ssize_t profiling_store(struct kobject *kobj,
+				   struct kobj_attribute *attr,
+				   const char *buf, size_t count)
+{
+	int ret;
+
+	profile_setup(buf);
+	profile_init();
+	if (!prof_buffer)
+		return -ENOMEM;
+	ret = create_proc_profile();
+	if (ret)
+		return ret;
+	return count;
+}
+KERNEL_ATTR_RW(profiling);
+#endif
+
 #ifdef CONFIG_KEXEC
 static ssize_t kexec_loaded_show(struct kobject *kobj,
 				 struct kobj_attribute *attr, char *buf)
@@ -109,6 +135,9 @@ static struct attribute * kernel_attrs[]
 	&uevent_seqnum_attr.attr,
 	&uevent_helper_attr.attr,
 #endif
+#ifdef CONFIG_PROFILING
+	&profiling_attr.attr,
+#endif
 #ifdef CONFIG_KEXEC
 	&kexec_loaded_attr.attr,
 	&kexec_crash_loaded_attr.attr,
diff -puN kernel/profile.c~dynamic-readprofile kernel/profile.c
--- linux-2.6.git/kernel/profile.c~dynamic-readprofile	2008-08-29 13:15:52.000000000 -0700
+++ linux-2.6.git-dave/kernel/profile.c	2008-08-29 13:18:50.000000000 -0700
@@ -50,11 +50,11 @@ static DEFINE_PER_CPU(int, cpu_profile_f
 static DEFINE_MUTEX(profile_flip_mutex);
 #endif /* CONFIG_SMP */
 
-static int __init profile_setup(char *str)
+int profile_setup(char *str)
 {
-	static char __initdata schedstr[] = "schedule";
-	static char __initdata sleepstr[] = "sleep";
-	static char __initdata kvmstr[] = "kvm";
+	static char schedstr[] = "schedule";
+	static char sleepstr[] = "sleep";
+	static char kvmstr[] = "kvm";
 	int par;
 
 	if (!strncmp(str, sleepstr, strlen(sleepstr))) {
@@ -100,14 +100,29 @@ static int __init profile_setup(char *st
 __setup("profile=", profile_setup);
 
 
-void __init profile_init(void)
+void profile_init(void)
 {
+	int buffer_bytes;
 	if (!prof_on)
 		return;
 
 	/* only text is profiled */
 	prof_len = (_etext - _stext) >> prof_shift;
-	prof_buffer = alloc_bootmem(prof_len*sizeof(atomic_t));
+	buffer_bytes = prof_len*sizeof(atomic_t);
+	if (!slab_is_available()) {
+		prof_buffer = alloc_bootmem(buffer_bytes);
+		return;
+	}
+
+	prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL);
+	if (prof_buffer)
+		return;
+
+	prof_buffer = alloc_pages_exact(buffer_bytes, GFP_KERNEL|__GFP_ZERO);
+	if (prof_buffer)
+		return;
+
+	prof_buffer = vmalloc(buffer_bytes);
 }
 
 /* Profile event notifications */
@@ -527,7 +542,7 @@ static void __init profile_nop(void *unu
 {
 }
 
-static int __init create_hash_tables(void)
+static int create_hash_tables(void)
 {
 	int cpu;
 
@@ -575,14 +590,14 @@ out_cleanup:
 #define create_hash_tables()			({ 0; })
 #endif
 
-static int __init create_proc_profile(void)
+int create_proc_profile(void)
 {
 	struct proc_dir_entry *entry;
 
 	if (!prof_on)
 		return 0;
 	if (create_hash_tables())
-		return -1;
+		return -ENOMEM;
 	entry = proc_create("profile", S_IWUSR | S_IRUGO,
 			    NULL, &proc_profile_operations);
 	if (!entry)
_