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Message-ID: <20070619195003.GA11718@c2.user-mode-linux.org>
Date: Tue, 19 Jun 2007 15:50:03 -0400
From: Jeff Dike <jdike@...toit.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
uml-devel <user-mode-linux-devel@...ts.sourceforge.net>
Subject: Re: [PATCH 2/2] UML - Add stack usage monitoring
On Tue, Jun 19, 2007 at 11:54:22AM -0700, Andrew Morton wrote:
> On Tue, 19 Jun 2007 14:42:45 -0400
> Jeff Dike <jdike@...toit.com> 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.
> >
>
> remind us again why the generic code is unsuitable?
It does something different - it will tell you the greatest stack
usage of any currently running process. What I want to be able to do
is run a workload and come back a few days later and see how close
anything came to running out of stack.
>
> > + for(p = stack; p < end; p++){
> > + if(*p != 0)
> > + if(left < lowest_to_date){
>
> Are there any plans to fix UML coding style?
You know I have been fixing it. I forgot to eyeball this patch for
style - fixed patch below.
Jeff
--
Work email - jdike at linux dot intel dot com
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 <jdike@...ux.intel.com>
--
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.
+
+ 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)
+ 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);
+ lowest_to_date = left;
+ }
+ spin_unlock(&low_water_lock);
+}
+
+#endif
Index: linux-2.6.21-mm/include/asm-um/thread_info.h
===================================================================
--- linux-2.6.21-mm.orig/include/asm-um/thread_info.h 2007-06-19 14:06:36.000000000 -0400
+++ linux-2.6.21-mm/include/asm-um/thread_info.h 2007-06-19 14:06:44.000000000 -0400
@@ -52,6 +52,20 @@ static inline struct thread_info *curren
return ti;
}
+#ifdef CONFIG_DEBUG_STACK_USAGE
+
+extern void check_stack_usage(struct thread_info *stack);
+
+#define alloc_thread_info(tsk) \
+ ((struct thread_info *) __get_free_pages(GFP_KERNEL | __GFP_ZERO, \
+ CONFIG_KERNEL_STACK_ORDER))
+
+#define free_thread_info(ti) ({ check_stack_usage(ti) ; \
+ free_pages((unsigned long)(ti), \
+ CONFIG_KERNEL_STACK_ORDER); })
+
+#else
+
/* thread information allocation */
#define alloc_thread_info(tsk) \
((struct thread_info *) __get_free_pages(GFP_KERNEL, \
@@ -61,6 +75,8 @@ static inline struct thread_info *curren
#endif
+#endif
+
#define PREEMPT_ACTIVE 0x10000000
#define TIF_SYSCALL_TRACE 0 /* syscall trace active */
Index: linux-2.6.21-mm/arch/um/defconfig
===================================================================
--- linux-2.6.21-mm.orig/arch/um/defconfig 2007-06-19 14:06:36.000000000 -0400
+++ linux-2.6.21-mm/arch/um/defconfig 2007-06-19 14:06:44.000000000 -0400
@@ -527,3 +527,4 @@ CONFIG_FORCED_INLINING=y
# CONFIG_RCU_TORTURE_TEST is not set
# CONFIG_GPROF is not set
# CONFIG_GCOV is not set
+# CONFIG_DEBUG_STACK_USAGE is not set
-
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