On Tue, 19 Jun 2007 15:50:03 -0400 Jeff Dike wrote:
> Add a machanism to see how much of a kernel stack is used. This
> allocates zeroed stacks and sees where the lowest non-zero byte is on
> process exit. It keeps track of the lowest value and logs values as
> they get lower.
>
> Signed-off-by: Jeff Dike <[email protected]>
> --
> arch/um/Kconfig.debug | 9 +++++++++
> arch/um/defconfig | 1 +
> arch/um/kernel/process.c | 29 +++++++++++++++++++++++++++++
> include/asm-um/thread_info.h | 16 ++++++++++++++++
> 4 files changed, 55 insertions(+)
>
> Index: linux-2.6.21-mm/arch/um/Kconfig.debug
> ===================================================================
> --- linux-2.6.21-mm.orig/arch/um/Kconfig.debug 2007-06-19 14:06:36.000000000 -0400
> +++ linux-2.6.21-mm/arch/um/Kconfig.debug 2007-06-19 14:06:44.000000000 -0400
> @@ -47,4 +47,13 @@ config GCOV
> If you're involved in UML kernel development and want to use gcov,
> say Y. If you're unsure, say N.
>
> +config DEBUG_STACK_USAGE
> + bool "Stack utilization instrumentation"
> + default N
> + help
> + Track the maximum kernel stack usage - this will look at each
> + kernel stack at process exit and log it if it's the deepest
> + stack seen so far.
Kconfig help text is indented 2 more spaces (by convention or
CodingStyle).
> +
> + This option will slow down process creation and destruction somewhat.
> endmenu
> Index: linux-2.6.21-mm/arch/um/kernel/process.c
> ===================================================================
> --- linux-2.6.21-mm.orig/arch/um/kernel/process.c 2007-06-19 14:06:36.000000000 -0400
> +++ linux-2.6.21-mm/arch/um/kernel/process.c 2007-06-19 15:48:20.000000000 -0400
> @@ -411,3 +411,32 @@ unsigned long arch_align_stack(unsigned
> return sp & ~0xf;
> }
> #endif
> +
> +#ifdef CONFIG_DEBUG_STACK_USAGE
> +
> +static DEFINE_SPINLOCK(low_water_lock);
> +static int lowest_to_date = THREAD_SIZE;
> +
> +void check_stack_usage(struct thread_info *s)
> +{
> + unsigned int *stack, *p, *end;
> + int left;
> +
> + stack = (unsigned int *) (s + 1);
> + end = (unsigned int *) ((unsigned long) s + THREAD_SIZE);
> + for (p = stack; p < end; p++) {
> + if(*p != 0)
if (*p != NULL)
or
if (*p)
> + break;
> + }
> +
> + left = (p - stack) * sizeof(*p);
> +
> + spin_lock(&low_water_lock);
> + if (left < lowest_to_date) {
> + printk("Greatest stack depth - %d bytes left\n", left);
Does UML need/use KERN_* facility levels in printk() calls?
> + lowest_to_date = left;
> + }
> + spin_unlock(&low_water_lock);
> +}
> +
> +#endif
---
~Randy
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