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2009-12-11tracing: Add stack trace to irqsoff tracerSteven Rostedt
The irqsoff and friends tracers help in finding causes of latency in the kernel. The also work with the function tracer to show what was happening when interrupts or preemption are disabled. But the function tracer has a bit of an overhead and can cause exagerated readings. Currently, when tracing with /proc/sys/kernel/ftrace_enabled = 0, where the function tracer is disabled, the information that is provided can end up being useless. For example, a 2 and a half millisecond latency only showed: # tracer: preemptirqsoff # # preemptirqsoff latency trace v1.1.5 on 2.6.32 # -------------------------------------------------------------------- # latency: 2463 us, #4/4, CPU#2 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:4) # ----------------- # | task: -4242 (uid:0 nice:0 policy:0 rt_prio:0) # ----------------- # => started at: _spin_lock_irqsave # => ended at: remove_wait_queue # # # _------=> CPU# # / _-----=> irqs-off # | / _----=> need-resched # || / _---=> hardirq/softirq # ||| / _--=> preempt-depth # |||| /_--=> lock-depth # |||||/ delay # cmd pid |||||| time | caller # \ / |||||| \ | / hackbenc-4242 2d.... 0us!: trace_hardirqs_off <-_spin_lock_irqsave hackbenc-4242 2...1. 2463us+: _spin_unlock_irqrestore <-remove_wait_queue hackbenc-4242 2...1. 2466us : trace_preempt_on <-remove_wait_queue The above lets us know that hackbench with pid 2463 grabbed a spin lock somewhere and enabled preemption at remove_wait_queue. This helps a little but where this actually happened is not informative. This patch adds the stack dump to the end of the irqsoff tracer. This provides the following output: hackbenc-4242 2d.... 0us!: trace_hardirqs_off <-_spin_lock_irqsave hackbenc-4242 2...1. 2463us+: _spin_unlock_irqrestore <-remove_wait_queue hackbenc-4242 2...1. 2466us : trace_preempt_on <-remove_wait_queue hackbenc-4242 2...1. 2467us : <stack trace> => sub_preempt_count => _spin_unlock_irqrestore => remove_wait_queue => free_poll_entry => poll_freewait => do_sys_poll => sys_poll => system_call_fastpath Now we see that the culprit of this latency was the free_poll_entry code. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-12tracing: do not update tracing_max_latency when tracer is stoppedCarsten Emde
The state of the function pair tracing_stop()/tracing_start() is correctly considered when tracer data are updated. However, the global and externally accessible variable tracing_max_latency is always updated - even when tracing is stopped. The update should only occur, if tracing was not stopped. Signed-off-by: Carsten Emde <C.Emde@osadl.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-12tracing: remove unused local variables in tracer probe functionsCarsten Emde
When the nsecs_to_usecs() conversion in probe_wakeup_sched_switch() and check_critical_timing() was moved to a later stage in order to avoid unnecessary computing, it was overlooked to remove the original variables, assignments and comments.. Signed-off-by: Carsten Emde <C.Emde@osadl.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-04tracing: use timestamp to determine start of latency tracesSteven Rostedt
Currently the latency tracers reset the ring buffer. Unfortunately if a commit is in process (due to a trace event), this can corrupt the ring buffer. When this happens, the ring buffer will detect the corruption and then permanently disable the ring buffer. The bug does not crash the system, but it does prevent further tracing after the bug is hit. Instead of reseting the trace buffers, the timestamp of the start of the trace is used instead. The buffers will still contain the previous data, but the output will not count any data that is before the timestamp of the trace. Note, this only affects the static trace output (trace) and not the runtime trace output (trace_pipe). The runtime trace output does not make sense for the latency tracers anyway. Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-03-04tracing: have latency tracers set the latency formatSteven Rostedt
The latency tracers (irqsoff, preemptoff, preemptirqsoff, and wakeup) are pretty useless with the default output format. This patch makes them automatically enable the latency format when they are selected. They also record the state of the latency option, and if it was not enabled when selected, they disable it on reset. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-17tracing: fix typing mistake in hint message and commentsWenji Huang
Impact: cleanup Fix incorrect hint message in code and typos in comments. Signed-off-by: Wenji Huang <wenji.huang@oracle.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-05trace: Remove unused trace_array_cpu parameterArnaldo Carvalho de Melo
Impact: cleanup Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-23trace: remove internal irqsoff disabling for trace outputSteven Rostedt
Impact: cleanup of duplicate features The trace output disables the ring buffer and prevents tracing to occur. The code in irqsoff to do the same thing is no longer needed. This patch removes it. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-16trace: set max latency variable to zero on defaultSteven Rostedt
Impact: trace max latencies on start of latency tracing This patch sets the max latency to zero whenever one of the irq variant tracers or the wakeup tracer is set to current tracer. Most developers expect to see output when starting up a latency tracer. But since the max_latency is already set to max, and it takes a latency greater than max_latency to be recorded, there is no trace. This is not the expected behavior and has even confused myself. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-16tracing/ftrace: change the type of the init() callbackFrederic Weisbecker
Impact: extend the ->init() method with the ability to fail This bring a way to know if the initialization of a tracer successed. A tracer must return 0 on success and a traditional error (ie: -ENOMEM) if it fails. If a tracer fails to init, it is free to print a detailed warn. The tracing api will not and switch to a new tracer will just return the error from the init callback. Note: this will be used for the return tracer. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-08ftrace: remove trace array ctrlSteven Rostedt
Impact: remove obsolete variable in trace_array structure With the new start / stop method of ftrace, the ctrl variable in the trace_array structure is now obsolete. Remove it. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-08ftrace: remove ctrl_update methodSteven Rostedt
Impact: Remove the ctrl_update tracer method With the new quick start/stop method of tracing, the ctrl_update method is out of date. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-08ftrace: irqsoff tracer incorrect resetSteven Rostedt
Impact: fix to irqsoff tracer output In converting to the new start / stop ftrace handling, the irqsoff tracer start called the irqsoff reset function. irqsoff tracer is not the same as the other traces, and it resets the buffers while searching for the longest latency. The reset that the irqsoff stop method calls disables the function tracing. That means that, by starting the tracer, the function tracer is disabled incorrectly. This patch simply removes the call to reset which keeps the function tracing enabled. Reset is not needed for the irqsoff stop method. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-06ftrace: restructure tracing start/stop infrastructureSteven Rostedt
Impact: change where tracing is started up and stopped Currently, when a new tracer is selected via echo'ing a tracer name into the current_tracer file, the startup is only done if tracing_enabled is set to one. If tracing_enabled is changed to zero (by echo'ing 0 into the tracing_enabled file) a full shutdown is performed. The full startup and shutdown of a tracer can be expensive and the user can lose out traces when echo'ing in 0 to the tracing_enabled file, because the process takes too long. There can also be places that the user would like to start and stop the tracer several times and doing the full startup and shutdown of a tracer might be too expensive. This patch performs the full startup and shutdown when a tracer is selected. It also adds a way to do a quick start or stop of a tracer. The quick version is just a flag that prevents the tracing from taking place, but the overhead of the code is still there. For example, the startup of a tracer may enable tracepoints, or enable the function tracer. The stop and start will just set a flag to have the tracer ignore the calls when the tracepoint or function trace is called. The overhead of the tracer may still be present when the tracer is stopped, but no tracing will occur. Setting the tracer to the 'nop' tracer (or any other tracer) will perform the shutdown of the tracer which will disable the tracepoint or disable the function tracer. The tracing_enabled file will simply start or stop tracing. This change is all internal. The end result for the user should be the same as before. If tracing_enabled is not set, no trace will happen. If tracing_enabled is set, then the trace will happen. The tracing_enabled variable is static between tracers. Enabling tracing_enabled and going to another tracer will keep tracing_enabled enabled. Same is true with disabling tracing_enabled. This patch will now provide a fast start/stop method to the users for enabling or disabling tracing. Note: There were two methods to the struct tracer that were never used: The methods start and stop. These were to be used as a hook to the reading of the trace output, but ended up not being necessary. These two methods are now used to enable the start and stop of each tracer, in case the tracer needs to do more than just not write into the buffer. For example, the irqsoff tracer must stop recording max latencies when tracing is stopped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-20ftrace: rename FTRACE to FUNCTION_TRACERSteven Rostedt
Due to confusion between the ftrace infrastructure and the gcc profiling tracer "ftrace", this patch renames the config options from FTRACE to FUNCTION_TRACER. The other two names that are offspring from FTRACE DYNAMIC_FTRACE and FTRACE_MCOUNT_RECORD will stay the same. This patch was generated mostly by script, and partially by hand. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-14ftrace: move pc counter in irqtraceSteven Rostedt
The assigning of the pc counter is in the wrong spot in the check_critical_timing function. The pc variable is used in the out jump. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-14ftrace: preempt disable over interrupt disableSteven Rostedt
With the new ring buffer infrastructure in ftrace, I'm trying to make ftrace a little more light weight. This patch converts a lot of the local_irq_save/restore into preempt_disable/enable. The original preempt count in a lot of cases has to be sent in as a parameter so that it can be recorded correctly. Some places were recording it incorrectly before anyway. This is also laying the ground work to make ftrace a little bit more reentrant, and remove all locking. The function tracers must still protect from reentrancy. Note: All the function tracers must be careful when using preempt_disable. It must do the following: resched = need_resched(); preempt_disable_notrace(); [...] if (resched) preempt_enable_no_resched_notrace(); else preempt_enable_notrace(); The reason is that if this function traces schedule() itself, the preempt_enable_notrace() will cause a schedule, which will lead us into a recursive failure. If we needed to reschedule before calling preempt_disable, we should have already scheduled. Since we did not, this is most likely that we should not and are probably inside a schedule function. If resched was not set, we still need to catch the need resched flag being set when preemption was off and the if case at the end will catch that for us. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-14ftrace: make work with new ring bufferSteven Rostedt
This patch ports ftrace over to the new ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-26ftrace: fix modular buildIngo Molnar
fix: ERROR: "start_critical_timings" [drivers/acpi/processor.ko] undefined! ERROR: "stop_critical_timings" [drivers/acpi/processor.ko] undefined! Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18ftrace: only trace preempt off with preempt tracerSteven Rostedt
When PREEMPT_TRACER and IRQSOFF_TRACER are both configured and irqsoff tracer is running, the preempt_off sections might also be traced. Thanks to Andrew Morton for pointing out my mistake of spin_lock disabling interrupts while he was reviewing ftrace.txt. Seems that my example I used actually hit this bug. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-05-26ftrace: remove printks from irqsoff traceSteven Rostedt
Printing out new max latencies was fine for the old RT tracer. But for mainline it is a bit messy. We also need to test if the run queue is locked before we can do the print. This means that we may not be printing out latencies if the run queue is locked on another CPU. This produces inconsistencies in the output. This patch simply removes the print altogether. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Cc: pq@iki.fi Cc: proski@gnu.org Cc: sandmann@redhat.com Cc: a.p.zijlstra@chello.nl Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23ftrace: irqsoff use raw_smp_processor_idSteven Rostedt
This patch changes the use of __get_cpu_var to explicitly calling raw_smp_processor_id and using the per_cpu() macro. On some debug configurations, the use of __get_cpu_var may cause ftrace to trigger and this can cause problems with the irqsoff tracing. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23ftrace: printk and trace irqsoff and wakeupsSteven Rostedt
printk called from wakeup critical timings and irqs off can cause deadlocks since printk might do a wakeup itself. If the call to printk happens with the runqueue lock held, it can deadlock. This patch protects the printk from being called in trace irqs off with a test to see if the runqueue for the current CPU is locked. If it is locked, the printk is skipped. The wakeup always holds the runqueue lock, so the printk is simply removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23ftrace: remove notraceIngo Molnar
now that we have a kbuild method for notrace, no need to pollute the C code with the annotations. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23ftrace: cleanupsIngo Molnar
clean up recent code. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23ftrace: add trace_function api for other tracers to useSteven Rostedt
A new check was added in the ftrace function that wont trace if the CPU trace buffer is disabled. Unfortunately, other tracers used ftrace() to write to the buffer after they disabled it. The new disable check makes these calls into a nop. This patch changes the __ftrace that is called without the check into a new api for the other tracers to use, called "trace_function". The other tracers use this interface instead when the trace CPU buffer is already disabled. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23ftrace: timestamp syncing, prepareIngo Molnar
rename and uninline now() to ftrace_now(). Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23ftrace: cleanupsIngo Molnar
factor out code and clean it up. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23ftrace: add self-testsSteven Rostedt
Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23ftrace: fix updates to max traceSteven Rostedt
This patch fixes some bugs to the updating of the max trace that was caused by implementing the new buffering. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23ftrace: irqs off smp_processor_id() fixSteven Rostedt
The irqsoff function tracer did a __get_cpu_var to determine if it should trace the function or not. The problem is that __get_cpu_var can preempt between getting the CPU and reading the cpu variable. This means that the cpu variable that is being read is not from the cpu being run on. At worst, this can give a false positive, where we trace the function when we should not. It will never give a false negative since we only want to trace when interrupts are disabled and we never preempt when they are. This fix adds a check after reading the irq flags to only trace if the interrupts are actually disabled. It also changes the reading of the cpu variable to use a raw_smp_processor_id since we now don't care if we preempt. We still catch that fact. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23ftrace: trace preempt off critical timingsSteven Rostedt
Add preempt off timings. A lot of kernel core code is taken from the RT patch latency trace that was written by Ingo Molnar. This adds "preemptoff" and "preemptirqsoff" to /debugfs/tracing/available_tracers Now instead of just tracing irqs off, preemption off can be selected to be recorded. When this is selected, it shares the same files as irqs off timings. One can either trace preemption off, irqs off, or one or the other off. By echoing "preemptoff" into /debugfs/tracing/current_tracer, recording of preempt off only is performed. "irqsoff" will only record the time irqs are disabled, but "preemptirqsoff" will take the total time irqs or preemption are disabled. Runtime switching of these options is now supported by simpling echoing in the appropriate trace name into /debugfs/tracing/current_tracer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23ftrace: trace irq disabled critical timingsSteven Rostedt
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>