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ftrace: trace irq disabled critical timings
This patch adds latency tracing for critical timings
(how long interrupts are disabled for).
"irqsoff" is added to /debugfs/tracing/available_tracers
Note:
tracing_max_latency
also holds the max latency for irqsoff (in usecs).
(default to large number so one must start latency tracing)
tracing_thresh
threshold (in usecs) to always print out if irqs off
is detected to be longer than stated here.
If irq_thresh is non-zero, then max_irq_latency
is ignored.
Here's an example of a trace with ftrace_enabled = 0
=======
preemption latency trace v1.1.5 on 2.6.24-rc7
Signed-off-by: Ingo Molnar <mingo@elte.hu>
--------------------------------------------------------------------
latency: 100 us, #3/3, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
-----------------
| task: swapper-0 (uid:0 nice:0 policy:0 rt_prio:0)
-----------------
=> started at: _spin_lock_irqsave+0x2a/0xb7
=> ended at: _spin_unlock_irqrestore+0x32/0x5f
_------=> CPU#
/ _-----=> irqs-off
| / _----=> need-resched
|| / _---=> hardirq/softirq
||| / _--=> preempt-depth
|||| /
||||| delay
cmd pid ||||| time | caller
\ / ||||| \ | /
swapper-0 1d.s3 0us+: _spin_lock_irqsave+0x2a/0xb7 (e1000_update_stats+0x47/0x64c [e1000])
swapper-0 1d.s3 100us : _spin_unlock_irqrestore+0x32/0x5f (e1000_update_stats+0x641/0x64c [e1000])
swapper-0 1d.s3 100us : trace_hardirqs_on_caller+0x75/0x89 (_spin_unlock_irqrestore+0x32/0x5f)
vim:ft=help
=======
And this is a trace with ftrace_enabled == 1
=======
preemption latency trace v1.1.5 on 2.6.24-rc7
--------------------------------------------------------------------
latency: 102 us, #12/12, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
-----------------
| task: swapper-0 (uid:0 nice:0 policy:0 rt_prio:0)
-----------------
=> started at: _spin_lock_irqsave+0x2a/0xb7
=> ended at: _spin_unlock_irqrestore+0x32/0x5f
_------=> CPU#
/ _-----=> irqs-off
| / _----=> need-resched
|| / _---=> hardirq/softirq
||| / _--=> preempt-depth
|||| /
||||| delay
cmd pid ||||| time | caller
\ / ||||| \ | /
swapper-0 1dNs3 0us+: _spin_lock_irqsave+0x2a/0xb7 (e1000_update_stats+0x47/0x64c [e1000])
swapper-0 1dNs3 46us : e1000_read_phy_reg+0x16/0x225 [e1000] (e1000_update_stats+0x5e2/0x64c [e1000])
swapper-0 1dNs3 46us : e1000_swfw_sync_acquire+0x10/0x99 [e1000] (e1000_read_phy_reg+0x49/0x225 [e1000])
swapper-0 1dNs3 46us : e1000_get_hw_eeprom_semaphore+0x12/0xa6 [e1000] (e1000_swfw_sync_acquire+0x36/0x99 [e1000])
swapper-0 1dNs3 47us : __const_udelay+0x9/0x47 (e1000_read_phy_reg+0x116/0x225 [e1000])
swapper-0 1dNs3 47us+: __delay+0x9/0x50 (__const_udelay+0x45/0x47)
swapper-0 1dNs3 97us : preempt_schedule+0xc/0x84 (__delay+0x4e/0x50)
swapper-0 1dNs3 98us : e1000_swfw_sync_release+0xc/0x55 [e1000] (e1000_read_phy_reg+0x211/0x225 [e1000])
swapper-0 1dNs3 99us+: e1000_put_hw_eeprom_semaphore+0x9/0x35 [e1000] (e1000_swfw_sync_release+0x50/0x55 [e1000])
swapper-0 1dNs3 101us : _spin_unlock_irqrestore+0xe/0x5f (e1000_update_stats+0x641/0x64c [e1000])
swapper-0 1dNs3 102us : _spin_unlock_irqrestore+0x32/0x5f (e1000_update_stats+0x641/0x64c [e1000])
swapper-0 1dNs3 102us : trace_hardirqs_on_caller+0x75/0x89 (_spin_unlock_irqrestore+0x32/0x5f)
vim:ft=help
=======
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Steven Rostedt
Thomas Gleixner
parent
352ad25aa4
commit
81d68a96a3
13 changed files with 531 additions and 31 deletions
402
kernel/trace/trace_irqsoff.c
Normal file
402
kernel/trace/trace_irqsoff.c
Normal file
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@ -0,0 +1,402 @@
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/*
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* trace irqs off criticall timings
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*
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* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
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* Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
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*
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* From code in the latency_tracer, that is:
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*
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* Copyright (C) 2004-2006 Ingo Molnar
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* Copyright (C) 2004 William Lee Irwin III
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*/
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#include <linux/kallsyms.h>
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#include <linux/debugfs.h>
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#include <linux/uaccess.h>
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#include <linux/module.h>
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#include <linux/ftrace.h>
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#include <linux/fs.h>
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#include "trace.h"
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static struct trace_array *irqsoff_trace __read_mostly;
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static int tracer_enabled __read_mostly;
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/*
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* Sequence count - we record it when starting a measurement and
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* skip the latency if the sequence has changed - some other section
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* did a maximum and could disturb our measurement with serial console
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* printouts, etc. Truly coinciding maximum latencies should be rare
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* and what happens together happens separately as well, so this doesnt
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* decrease the validity of the maximum found:
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*/
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static __cacheline_aligned_in_smp unsigned long max_sequence;
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#ifdef CONFIG_FTRACE
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/*
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* irqsoff uses its own tracer function to keep the overhead down:
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*/
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static void notrace
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irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip)
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{
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struct trace_array *tr = irqsoff_trace;
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struct trace_array_cpu *data;
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unsigned long flags;
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long disabled;
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int cpu;
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if (likely(!tracer_enabled))
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return;
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local_save_flags(flags);
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if (!irqs_disabled_flags(flags))
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return;
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cpu = raw_smp_processor_id();
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data = tr->data[cpu];
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disabled = atomic_inc_return(&data->disabled);
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if (likely(disabled == 1))
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ftrace(tr, data, ip, parent_ip, flags);
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atomic_dec(&data->disabled);
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}
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static struct ftrace_ops trace_ops __read_mostly =
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{
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.func = irqsoff_tracer_call,
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};
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#endif /* CONFIG_FTRACE */
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/*
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* Should this new latency be reported/recorded?
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*/
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static int notrace report_latency(cycle_t delta)
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{
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if (tracing_thresh) {
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if (delta < tracing_thresh)
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return 0;
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} else {
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if (delta <= tracing_max_latency)
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return 0;
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}
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return 1;
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}
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static void notrace
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check_critical_timing(struct trace_array *tr,
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struct trace_array_cpu *data,
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unsigned long parent_ip,
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int cpu)
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{
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unsigned long latency, t0, t1;
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cycle_t T0, T1, T2, delta;
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unsigned long flags;
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/*
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* usecs conversion is slow so we try to delay the conversion
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* as long as possible:
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*/
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T0 = data->preempt_timestamp;
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T1 = now(cpu);
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delta = T1-T0;
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local_save_flags(flags);
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if (!report_latency(delta))
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goto out;
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ftrace(tr, data, CALLER_ADDR0, parent_ip, flags);
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/*
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* Update the timestamp, because the trace entry above
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* might change it (it can only get larger so the latency
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* is fair to be reported):
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*/
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T2 = now(cpu);
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delta = T2-T0;
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latency = nsecs_to_usecs(delta);
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if (data->critical_sequence != max_sequence)
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goto out;
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tracing_max_latency = delta;
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t0 = nsecs_to_usecs(T0);
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t1 = nsecs_to_usecs(T1);
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data->critical_end = parent_ip;
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update_max_tr_single(tr, current, cpu);
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if (tracing_thresh)
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printk(KERN_INFO "(%16s-%-5d|#%d): %lu us critical section "
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"violates %lu us threshold.\n"
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" => started at timestamp %lu: ",
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current->comm, current->pid,
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raw_smp_processor_id(),
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latency, nsecs_to_usecs(tracing_thresh), t0);
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else
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printk(KERN_INFO "(%16s-%-5d|#%d):"
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" new %lu us maximum-latency "
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"critical section.\n => started at timestamp %lu: ",
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current->comm, current->pid,
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raw_smp_processor_id(),
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latency, t0);
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print_symbol(KERN_CONT "<%s>\n", data->critical_start);
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printk(KERN_CONT " => ended at timestamp %lu: ", t1);
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print_symbol(KERN_CONT "<%s>\n", data->critical_end);
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dump_stack();
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t1 = nsecs_to_usecs(now(cpu));
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printk(KERN_CONT " => dump-end timestamp %lu\n\n", t1);
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max_sequence++;
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out:
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data->critical_sequence = max_sequence;
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data->preempt_timestamp = now(cpu);
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tracing_reset(data);
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ftrace(tr, data, CALLER_ADDR0, parent_ip, flags);
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}
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static inline void notrace
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start_critical_timing(unsigned long ip, unsigned long parent_ip)
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{
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int cpu;
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struct trace_array *tr = irqsoff_trace;
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struct trace_array_cpu *data;
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unsigned long flags;
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if (likely(!tracer_enabled))
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return;
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cpu = raw_smp_processor_id();
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data = tr->data[cpu];
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if (unlikely(!data) || unlikely(!data->trace) ||
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data->critical_start || atomic_read(&data->disabled))
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return;
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atomic_inc(&data->disabled);
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data->critical_sequence = max_sequence;
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data->preempt_timestamp = now(cpu);
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data->critical_start = parent_ip;
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tracing_reset(data);
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local_save_flags(flags);
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ftrace(tr, data, ip, parent_ip, flags);
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atomic_dec(&data->disabled);
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}
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static inline void notrace
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stop_critical_timing(unsigned long ip, unsigned long parent_ip)
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{
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int cpu;
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struct trace_array *tr = irqsoff_trace;
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struct trace_array_cpu *data;
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unsigned long flags;
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if (likely(!tracer_enabled))
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return;
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cpu = raw_smp_processor_id();
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data = tr->data[cpu];
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if (unlikely(!data) || unlikely(!data->trace) ||
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!data->critical_start || atomic_read(&data->disabled))
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return;
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atomic_inc(&data->disabled);
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local_save_flags(flags);
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ftrace(tr, data, ip, parent_ip, flags);
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check_critical_timing(tr, data, parent_ip, cpu);
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data->critical_start = 0;
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atomic_dec(&data->disabled);
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}
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void notrace start_critical_timings(void)
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{
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unsigned long flags;
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local_save_flags(flags);
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if (irqs_disabled_flags(flags))
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start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
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}
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void notrace stop_critical_timings(void)
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{
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unsigned long flags;
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local_save_flags(flags);
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if (irqs_disabled_flags(flags))
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stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
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}
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#ifdef CONFIG_PROVE_LOCKING
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void notrace time_hardirqs_on(unsigned long a0, unsigned long a1)
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{
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unsigned long flags;
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local_save_flags(flags);
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if (irqs_disabled_flags(flags))
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stop_critical_timing(a0, a1);
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}
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void notrace time_hardirqs_off(unsigned long a0, unsigned long a1)
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{
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unsigned long flags;
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local_save_flags(flags);
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if (irqs_disabled_flags(flags))
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start_critical_timing(a0, a1);
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}
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#else /* !CONFIG_PROVE_LOCKING */
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/*
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* Stubs:
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*/
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void early_boot_irqs_off(void)
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{
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}
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void early_boot_irqs_on(void)
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{
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}
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void trace_softirqs_on(unsigned long ip)
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{
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}
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void trace_softirqs_off(unsigned long ip)
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{
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}
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inline void print_irqtrace_events(struct task_struct *curr)
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{
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}
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/*
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* We are only interested in hardirq on/off events:
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*/
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void notrace trace_hardirqs_on(void)
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{
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unsigned long flags;
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local_save_flags(flags);
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if (irqs_disabled_flags(flags))
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stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
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}
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EXPORT_SYMBOL(trace_hardirqs_on);
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void notrace trace_hardirqs_off(void)
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{
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unsigned long flags;
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local_save_flags(flags);
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if (irqs_disabled_flags(flags))
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start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
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}
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EXPORT_SYMBOL(trace_hardirqs_off);
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void notrace trace_hardirqs_on_caller(unsigned long caller_addr)
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{
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unsigned long flags;
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local_save_flags(flags);
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if (irqs_disabled_flags(flags))
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stop_critical_timing(CALLER_ADDR0, caller_addr);
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}
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EXPORT_SYMBOL(trace_hardirqs_on_caller);
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void notrace trace_hardirqs_off_caller(unsigned long caller_addr)
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{
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unsigned long flags;
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local_save_flags(flags);
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if (irqs_disabled_flags(flags))
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start_critical_timing(CALLER_ADDR0, caller_addr);
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}
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EXPORT_SYMBOL(trace_hardirqs_off_caller);
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#endif /* CONFIG_PROVE_LOCKING */
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static void start_irqsoff_tracer(struct trace_array *tr)
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{
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tracer_enabled = 1;
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register_ftrace_function(&trace_ops);
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}
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static void stop_irqsoff_tracer(struct trace_array *tr)
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{
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unregister_ftrace_function(&trace_ops);
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tracer_enabled = 0;
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}
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static void irqsoff_tracer_init(struct trace_array *tr)
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{
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irqsoff_trace = tr;
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/* make sure that the tracer is visibel */
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smp_wmb();
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if (tr->ctrl)
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start_irqsoff_tracer(tr);
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}
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static void irqsoff_tracer_reset(struct trace_array *tr)
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{
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if (tr->ctrl)
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stop_irqsoff_tracer(tr);
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}
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static void irqsoff_tracer_ctrl_update(struct trace_array *tr)
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{
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if (tr->ctrl)
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start_irqsoff_tracer(tr);
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else
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stop_irqsoff_tracer(tr);
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}
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static void notrace irqsoff_tracer_open(struct trace_iterator *iter)
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{
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/* stop the trace while dumping */
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if (iter->tr->ctrl)
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stop_irqsoff_tracer(iter->tr);
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}
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static void notrace irqsoff_tracer_close(struct trace_iterator *iter)
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{
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if (iter->tr->ctrl)
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start_irqsoff_tracer(iter->tr);
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}
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static struct tracer irqsoff_tracer __read_mostly =
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{
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.name = "irqsoff",
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.init = irqsoff_tracer_init,
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.reset = irqsoff_tracer_reset,
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.open = irqsoff_tracer_open,
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.close = irqsoff_tracer_close,
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.ctrl_update = irqsoff_tracer_ctrl_update,
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.print_max = 1,
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};
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__init static int init_irqsoff_tracer(void)
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{
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register_tracer(&irqsoff_tracer);
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return 0;
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}
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device_initcall(init_irqsoff_tracer);
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