* Ingo Molnar <[email protected]> wrote:
> > Adding new runs is easy. Changing the harness is hard ;-)
>
> ok. How about a CONFIG_DEBUG_NO_OVERHEAD option, that would default to
> disabled but which you could set to y. Then we could make all the more
> expensive debug options:
>
> default y if !CONFIG_DEBUG_NO_OVERHEAD
>
> this would still mean you'd have to turn off CONFIG_DEBUG_NO_OVERHEAD,
> but it would be automatically maintainable for you after that initial
> effort, and we'd be careful to always flag new debugging options with
> this flag, if they are expensive. And initially i'd define "expensive"
> as "anything that adds runtime overhead".
the patch below implements this and categorizes all debug options based
on whether they have runtime overhead or not.
(i have left out debug options that are non-transparent - i.e. which
print lots of stuff to the syslog like DEBUG_KOBJECT.)
Ingo
Index: linux/lib/Kconfig.debug
===================================================================
--- linux.orig/lib/Kconfig.debug
+++ linux/lib/Kconfig.debug
@@ -54,6 +54,15 @@ config DEBUG_KERNEL
Say Y here if you are developing drivers or trying to debug and
identify kernel problems.
+config DEBUG_KERNEL_RUNTIME_OVERHEAD
+ bool "Enable new debug options by default"
+ default y
+ help
+ Say Y here if you want to have new debugging options
+ enabled by default even if they cause runtime overhead.
+ (you can still disable/enable them manually, independently
+ of this switch)
+
config LOG_BUF_SHIFT
int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" if DEBUG_KERNEL
range 12 21
@@ -113,7 +122,7 @@ config DEBUG_SLAB
config DEBUG_SLAB_LEAK
bool "Slab memory leak debugging"
depends on DEBUG_SLAB
- default y
+ default y if DEBUG_KERNEL_RUNTIME_OVERHEAD
help
Enable /proc/slab_allocators - provides detailed information about
which parts of the kernel are using slab objects. May be used for
@@ -122,7 +131,7 @@ config DEBUG_SLAB_LEAK
config DEBUG_PREEMPT
bool "Debug preemptible kernel"
depends on DEBUG_KERNEL && PREEMPT
- default y
+ default y if DEBUG_KERNEL_RUNTIME_OVERHEAD
depends on TRACE_IRQFLAGS_SUPPORT
help
If you say Y here then the kernel will use a debug variant of the
@@ -132,7 +141,7 @@ config DEBUG_PREEMPT
config DEBUG_MUTEXES
bool "Mutex debugging, basic checks"
- default n
+ default y if DEBUG_KERNEL_RUNTIME_OVERHEAD
depends on DEBUG_KERNEL
help
This feature allows mutex semantics violations to be detected and
@@ -140,7 +149,7 @@ config DEBUG_MUTEXES
config DEBUG_MUTEX_ALLOC
bool "Detect incorrect freeing of live mutexes"
- default n
+ default y if DEBUG_KERNEL_RUNTIME_OVERHEAD
depends on DEBUG_MUTEXES
help
This feature will check whether any held mutex is incorrectly
@@ -150,7 +159,7 @@ config DEBUG_MUTEX_ALLOC
config DEBUG_MUTEX_DEADLOCKS
bool "Detect mutex related deadlocks"
- default n
+ default y if DEBUG_KERNEL_RUNTIME_OVERHEAD
depends on DEBUG_MUTEXES
help
This feature will automatically detect and report mutex related
@@ -158,7 +167,7 @@ config DEBUG_MUTEX_DEADLOCKS
config DEBUG_RT_MUTEXES
bool "RT Mutex debugging, deadlock detection"
- default n
+ default y if DEBUG_KERNEL_RUNTIME_OVERHEAD
depends on DEBUG_KERNEL && RT_MUTEXES
help
This allows rt mutex semantics violations and rt mutex related
@@ -166,7 +175,7 @@ config DEBUG_RT_MUTEXES
config DEBUG_PI_LIST
bool
- default n
+ default y if DEBUG_KERNEL_RUNTIME_OVERHEAD
depends on DEBUG_RT_MUTEXES
config RT_MUTEX_TESTER
@@ -179,6 +188,7 @@ config RT_MUTEX_TESTER
config DEBUG_SPINLOCK
bool "Spinlock debugging"
depends on DEBUG_KERNEL
+ default y if DEBUG_KERNEL_RUNTIME_OVERHEAD
help
Say Y here and build SMP to catch missing spinlock initialization
and certain other kinds of spinlock errors commonly made. This is
@@ -188,7 +198,7 @@ config DEBUG_SPINLOCK
config PROVE_SPIN_LOCKING
bool "Prove spin-locking correctness"
depends on X86
- default n
+ default y if DEBUG_KERNEL_RUNTIME_OVERHEAD
help
This feature enables the kernel to prove that all spinlock
locking that occurs in the kernel runtime is mathematically
@@ -226,7 +236,7 @@ config PROVE_SPIN_LOCKING
config PROVE_RW_LOCKING
bool "Prove rw-locking correctness"
depends on X86
- default n
+ default y if DEBUG_KERNEL_RUNTIME_OVERHEAD
help
This feature enables the kernel to prove that all rwlock
locking that occurs in the kernel runtime is mathematically
@@ -264,7 +274,7 @@ config PROVE_RW_LOCKING
config PROVE_MUTEX_LOCKING
bool "Prove mutex-locking correctness"
depends on X86
- default n
+ default y if DEBUG_KERNEL_RUNTIME_OVERHEAD
help
This feature enables the kernel to prove that all mutexlock
locking that occurs in the kernel runtime is mathematically
@@ -302,7 +312,7 @@ config PROVE_MUTEX_LOCKING
config PROVE_RWSEM_LOCKING
bool "Prove rwsem-locking correctness"
depends on X86
- default n
+ default y if DEBUG_KERNEL_RUNTIME_OVERHEAD
help
This feature enables the kernel to prove that all rwsemlock
locking that occurs in the kernel runtime is mathematically
@@ -348,7 +358,7 @@ config LOCKDEP
config DEBUG_LOCKDEP
bool "Lock dependency engine debugging"
depends on LOCKDEP
- default y
+ default y if DEBUG_KERNEL_RUNTIME_OVERHEAD
depends on TRACE_IRQFLAGS_SUPPORT
help
If you say Y here, the lock dependency engine will do
@@ -363,6 +373,7 @@ config TRACE_IRQFLAGS
config DEBUG_SPINLOCK_SLEEP
bool "Sleep-inside-spinlock checking"
+ default y if DEBUG_KERNEL_RUNTIME_OVERHEAD
depends on DEBUG_KERNEL
help
If you say Y here, various routines which may sleep will become very
@@ -390,6 +401,7 @@ config DEBUG_KOBJECT
config DEBUG_HIGHMEM
bool "Highmem debugging"
depends on DEBUG_KERNEL && HIGHMEM
+ default y if DEBUG_KERNEL_RUNTIME_OVERHEAD
help
This options enables addition error checking for high memory systems.
Disable for production systems.
@@ -398,7 +410,7 @@ config DEBUG_BUGVERBOSE
bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED
depends on BUG
depends on ARM || ARM26 || M32R || M68K || SPARC32 || SPARC64 || X86_32 || FRV
- default !EMBEDDED
+ default y if DEBUG_KERNEL_RUNTIME_OVERHEAD && !EMBEDDED
help
Say Y here to make BUG() panics output the file name and line number
of the BUG call as well as the EIP and oops trace. This aids
@@ -437,6 +449,7 @@ config DEBUG_FS
config DEBUG_VM
bool "Debug VM"
depends on DEBUG_KERNEL
+ default y if DEBUG_KERNEL_RUNTIME_OVERHEAD
help
Enable this to turn on extended checks in the virtual-memory system
that may impact performance.
@@ -446,7 +459,7 @@ config DEBUG_VM
config FRAME_POINTER
bool "Compile the kernel with frame pointers"
depends on DEBUG_KERNEL && (X86 || CRIS || M68K || M68KNOMMU || FRV || UML)
- default y
+ default y if DEBUG_KERNEL_RUNTIME_OVERHEAD
help
If you say Y here the resulting kernel image will be slightly larger
and slower, but it might give very useful debugging information on
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