profiling: dynamically enable readprofile at runtime
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>
diff --git a/Documentation/ABI/testing/sysfs-profiling b/Documentation/ABI/testing/sysfs-profiling
new file mode 100644
index 0000000..b02d8b8
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-profiling
@@ -0,0 +1,13 @@
+What: /sys/kernel/profile
+Date: September 2008
+Contact: Dave Hansen <dave@linux.vnet.ibm.com>
+Description:
+ /sys/kernel/profile is the runtime equivalent
+ of the boot-time profile= option.
+
+ You can get the same effect running:
+
+ echo 2 > /sys/kernel/profile
+
+ as you would by issuing profile=2 on the boot
+ command line.