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Message-Id: <E1Ixner-0002Ct-IQ@dorka.pomaz.szeredi.hu>
Date: Thu, 29 Nov 2007 18:58:41 +0100
From: Miklos Szeredi <miklos@...redi.hu>
To: mingo@...e.hu
CC: jdike@...toit.com, user-mode-linux-devel@...ts.sourceforge.net,
linux-kernel@...r.kernel.org
Subject: Re: scheduling anomaly on uml (was: -rt doesn't compile for UML)
> > On Thu, Nov 29, 2007 at 11:19:40AM +0100, Miklos Szeredi wrote:
> > > date-7119 0.... 15636591us!: schedule <bash-502> (0 0)
> > > bash-502 0.... 15643908us!: schedule <date-7119> (0 0)
> > > bash-502 0.... 15646250us!: schedule <date-7120> (0 0)
> >
> > How exactly did you end up getting this data?
This:
http://people.redhat.com/mingo/latency-tracing-patches/tracing-QuickStart.txt
and some hacking, which is probably not very useful:
Index: linux/include/asm-um/rtc.h
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux/include/asm-um/rtc.h 2007-11-28 17:41:42.000000000 +0100
@@ -0,0 +1 @@
+/* stub for the latency tracer */
Index: linux/include/asm-um/irqflags.h
===================================================================
--- linux.orig/include/asm-um/irqflags.h 2007-11-28 17:36:21.000000000 +0100
+++ linux/include/asm-um/irqflags.h 2007-11-28 17:41:42.000000000 +0100
@@ -1,6 +1,9 @@
#ifndef __UM_IRQFLAGS_H
#define __UM_IRQFLAGS_H
-/* Empty for now */
+static inline int raw_irqs_disabled_flags(unsigned long flags)
+{
+ return 0;
+}
#endif
Index: linux/kernel/latency_trace.c
===================================================================
--- linux.orig/kernel/latency_trace.c 2007-11-28 17:41:35.000000000 +0100
+++ linux/kernel/latency_trace.c 2007-11-29 16:05:45.000000000 +0100
@@ -26,6 +26,7 @@
#include <asm/unistd.h>
#include <asm/asm-offsets.h>
#include <asm/rtc.h>
+#include <asm/irqflags.h>
#include <linux/stacktrace.h>
#ifndef DEFINE_RAW_SPINLOCK
@@ -59,6 +60,8 @@ static unsigned long notrace cycles_to_u
delta = mulhwu(tb_to_us, delta);
#elif defined(CONFIG_ARM)
delta = mach_cycles_to_usecs(delta);
+#elif defined(CONFIG_UML)
+ /* Dunno */
#else
#error Implement cycles_to_usecs.
#endif
@@ -188,7 +191,7 @@ static int report_latency(cycle_t delta)
/*
* Number of per-CPU trace entries:
*/
-#define MAX_TRACE (65536UL*16UL)
+#define MAX_TRACE (1024UL*16UL)
#define CMDLINE_BYTES 16
@@ -655,7 +658,7 @@ again:
entry->cpu = cpu;
#endif
entry->flags = (irqs_off() ? TRACE_FLAG_IRQS_OFF : 0) |
- (irqs_disabled_flags(flags) ? TRACE_FLAG_IRQS_HARD_OFF : 0)|
+ (raw_irqs_disabled_flags(flags) ? TRACE_FLAG_IRQS_HARD_OFF : 0)|
((pc & HARDIRQ_MASK) ? TRACE_FLAG_HARDIRQ : 0) |
((pc & SOFTIRQ_MASK) ? TRACE_FLAG_SOFTIRQ : 0) |
(need_resched() ? TRACE_FLAG_NEED_RESCHED : 0) |
@@ -2709,7 +2712,7 @@ void __init init_tracer(void)
for_each_possible_cpu(cpu) {
tr = cpu_traces + cpu;
- array = tracer_alloc_bootmem(size);
+ array = alloc_bootmem(size);
if (!array) {
printk(KERN_ERR
"CPU#%d: failed to allocate %ld bytes trace buffer!\n",
@@ -2723,7 +2726,7 @@ void __init init_tracer(void)
tr->cpu = cpu;
tr->trace = array;
- array = tracer_alloc_bootmem(size);
+ array = alloc_bootmem(size);
if (!array) {
printk(KERN_ERR
"CPU#%d: failed to allocate %ld bytes max-trace buffer!\n",
@@ -2742,7 +2745,7 @@ void __init init_tracer(void)
* trace entries for the first cpu-trace structure:
*/
size = sizeof(struct trace_entry)*MAX_TRACE*num_possible_cpus();
- array = tracer_alloc_bootmem(size);
+ array = alloc_bootmem(size);
if (!array) {
printk(KERN_ERR
"failed to allocate %ld bytes out-trace buffer!\n",
Index: linux/arch/um/sys-i386/sysrq.c
===================================================================
--- linux.orig/arch/um/sys-i386/sysrq.c 2007-10-09 22:31:38.000000000 +0200
+++ linux/arch/um/sys-i386/sysrq.c 2007-11-29 16:20:12.000000000 +0100
@@ -7,6 +7,7 @@
#include "linux/smp.h"
#include "linux/sched.h"
#include "linux/kallsyms.h"
+#include "linux/stacktrace.h"
#include "asm/ptrace.h"
#include "sysrq.h"
@@ -99,3 +100,26 @@ void show_trace(struct task_struct* task
printk("\n");
}
+void save_stack_trace(struct stack_trace *trace)
+{
+ unsigned long ebp;
+ struct thread_info *tinfo;
+ unsigned long stack;
+ unsigned long addr;
+
+ asm ("movl %%ebp, %0" : "=r" (ebp) : );
+
+ tinfo = (struct thread_info *)
+ ((unsigned long)(&stack) & (~(THREAD_SIZE - 1)));
+
+ while (valid_stack_ptr(tinfo, (void *)ebp)) {
+ addr = *(unsigned long *)(ebp + 4);
+ if (trace->skip > 0) {
+ trace->skip--;
+ } else if (trace->nr_entries < trace->max_entries) {
+ trace->entries[trace->nr_entries++] = addr;
+ }
+ ebp = *(unsigned long *)ebp;
+ }
+}
+
Index: linux/kernel/sched.c
===================================================================
--- linux.orig/kernel/sched.c 2007-11-29 16:29:08.000000000 +0100
+++ linux/kernel/sched.c 2007-11-29 16:29:20.000000000 +0100
@@ -3658,6 +3658,7 @@ need_resched_nonpreemptible:
next = pick_next_task(rq, prev);
trace_all_runnable_tasks(rq);
+ trace_special_sym();
sched_info_switch(prev, next);
-
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