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profiling: dynamically enable readprofile at runtime

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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.

This should fix the compile issue with allmodconfig.  I've compile-tested
on a bunch more configs now including a few more architectures.

Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Dave Hansen 2008-10-15 22:01:46 -07:00 • committed by Linus Torvalds
parent 0c2d64fb6c
commit 22b8ce9470
4 changed files with 84 additions and 13 deletions
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35
kernel/ksysfs.c
View file

@ -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 +54,37 @@ static ssize_t uevent_helper_store(struct kobject *kobj,
KERNEL_ATTR_RW(uevent_helper);
#endif
#ifdef CONFIG_PROFILING
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;
if (prof_on)
return -EEXIST;
/*
* This eventually calls into get_option() which
* has a ton of callers and is not const. It is
* easiest to cast it away here.
*/
profile_setup((char *)buf);
ret = profile_init();
if (ret)
return ret;
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 +141,9 @@ 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,