Re: ksoftirqd using mysteriously high amounts of CPU time

[Andrew Morton <akpm@osdl.org>]

Brad Laue <brad@brad-x.com> wrote:
>
>  Brad Laue wrote:
>  > Hopefully the attached shows some irregularity. If not, I'll have to 
>  > reply back in a few weeks when the problem recurs over the course of time.
> 
>  And without further ado, the attachment. It's been a long day. :)

It beats me.  Something must be waking up ksoftirqd all the time.

If you have time, could you please apply the below, then wait for ksoftirqd
to go bad again and then run:


	dmesg -c
	echo 1 > /proc/sys/debug/0 ; sleep 1; echo 0 > /proc/sys/debug/0
	dmesg -s 1000000 > /tmp/foo

and then send foo?


diff -puN include/linux/kernel.h~proc-sys-debug include/linux/kernel.h
--- 25/include/linux/kernel.h~proc-sys-debug	2004-02-25 23:12:56.000000000 -0800
+++ 25-akpm/include/linux/kernel.h	2004-02-25 23:12:57.000000000 -0800
@@ -214,6 +214,8 @@ extern void dump_stack(void);
 	1; \
 })
 
+extern int proc_sys_debug[8];
+
 #endif /* __KERNEL__ */
 
 #define SI_LOAD_SHIFT	16
diff -puN -L kernel/ksyms.c /dev/null /dev/null
diff -puN kernel/sysctl.c~proc-sys-debug kernel/sysctl.c
--- 25/kernel/sysctl.c~proc-sys-debug	2004-02-25 23:12:56.000000000 -0800
+++ 25-akpm/kernel/sysctl.c	2004-02-25 23:21:37.000000000 -0800
@@ -849,7 +849,26 @@ static ctl_table fs_table[] = {
 	{ .ctl_name = 0 }
 };
 
+int proc_sys_debug[8];
+EXPORT_SYMBOL(proc_sys_debug);
+
 static ctl_table debug_table[] = {
+	{1, "0", &proc_sys_debug[0], sizeof(int), 0644, NULL,
+	 &proc_dointvec_minmax, &sysctl_intvec, NULL, NULL, NULL},
+	{2, "1", &proc_sys_debug[1], sizeof(int), 0644, NULL,
+	 &proc_dointvec_minmax, &sysctl_intvec, NULL, NULL, NULL},
+	{3, "2", &proc_sys_debug[2], sizeof(int), 0644, NULL,
+	 &proc_dointvec_minmax, &sysctl_intvec, NULL, NULL, NULL},
+	{4, "3", &proc_sys_debug[3], sizeof(int), 0644, NULL,
+	 &proc_dointvec_minmax, &sysctl_intvec, NULL, NULL, NULL},
+	{5, "4", &proc_sys_debug[4], sizeof(int), 0644, NULL,
+	 &proc_dointvec_minmax, &sysctl_intvec, NULL, NULL, NULL},
+	{6, "5", &proc_sys_debug[5], sizeof(int), 0644, NULL,
+	 &proc_dointvec_minmax, &sysctl_intvec, NULL, NULL, NULL},
+	{7, "6", &proc_sys_debug[6], sizeof(int), 0644, NULL,
+	 &proc_dointvec_minmax, &sysctl_intvec, NULL, NULL, NULL},
+	{8, "7", &proc_sys_debug[7], sizeof(int), 0644, NULL,
+	 &proc_dointvec_minmax, &sysctl_intvec, NULL, NULL, NULL},
 	{ .ctl_name = 0 }
 };
 

_
 kernel/softirq.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletion(-)

diff -puN kernel/softirq.c~a kernel/softirq.c
--- 25/kernel/softirq.c~a	2004-03-11 02:05:20.000000000 -0800
+++ 25-akpm/kernel/softirq.c	2004-03-11 02:06:02.000000000 -0800
@@ -54,8 +54,13 @@ static inline void wakeup_softirqd(void)
 	/* Interrupts are disabled: no need to stop preemption */
 	struct task_struct *tsk = __get_cpu_var(ksoftirqd);
 
-	if (tsk && tsk->state != TASK_RUNNING)
+	if (tsk && tsk->state != TASK_RUNNING) {
+		if (proc_sys_debug[0]) {
+			printk("%s wakes ksoftirqd\n", current->comm);
+			dump_stack();
+		}
 		wake_up_process(tsk);
+	}
 }
 
 /*

_