[PATCH for tip] ftrace: remove latency_trace document

KOSAKI Motohiro
2009-03-07T14:54:21Z

Subject: [PATCH] remove latency_trace document

Currently, there aren't "Latency tracer" and latency_trace file.
Then, its documentation is removed too.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
---
Documentation/ftrace.txt | 550 +--------------------------------------------
1 files changed, 13 insertions(+), 537 deletions(-)

diff --git a/Documentation/ftrace.txt b/Documentation/ftrace.txt
index 22614be..d124e6a 100644
--- a/Documentation/ftrace.txt
+++ b/Documentation/ftrace.txt
@@ -29,7 +29,7 @@ means that the list of tracers can always grow).

The File System
---------------
-
+1
Ftrace uses the debugfs file system to hold the control files as
well as the files to display output.

@@ -73,26 +73,19 @@ of ftrace. Here is a list of some of the key files:
This file holds the output of the trace in a human
readable format (described below).

- latency_trace:
-
- This file shows the same trace but the information
- is organized more to display possible latencies
- in the system (described below).
-
trace_pipe:

The output is the same as the "trace" file but this
file is meant to be streamed with live tracing.
Reads from this file will block until new data
- is retrieved. Unlike the "trace" and "latency_trace"
- files, this file is a consumer. This means reading
- from this file causes sequential reads to display
- more current data. Once data is read from this
- file, it is consumed, and will not be read
- again with a sequential read. The "trace" and
- "latency_trace" files are static, and if the
- tracer is not adding more data, they will display
- the same information every time they are read.
+ is retrieved. Unlike the "trace" file, this file
+ is a consumer. This means reading from this file
+ causes sequential reads to display more current data.
+ Once data is read from this file, it is consumed,
+ and will not be read again with a sequential read.
+ The "trace" files is static, and if the tracer is not
+ adding more data, they will display the same information
+ every time they are read.

trace_options:

@@ -105,10 +98,10 @@ of ftrace. Here is a list of some of the key files:
Some of the tracers record the max latency.
For example, the time interrupts are disabled.
This time is saved in this file. The max trace
- will also be stored, and displayed by either
- "trace" or "latency_trace". A new max trace will
- only be recorded if the latency is greater than
- the value in this file. (in microseconds)
+ will also be stored, and displayed by "trace".
+ A new max trace will only be recorded if the
+ latency is greater than the value in this file.
+ (in microseconds)

buffer_size_kb:

@@ -192,25 +185,6 @@ Here is the list of current tracers that may be configured.

Traces the context switches and wakeups between tasks.

- "irqsoff"
-
- Traces the areas that disable interrupts and saves
- the trace with the longest max latency.
- See tracing_max_latency. When a new max is recorded,
- it replaces the old trace. It is best to view this
- trace via the latency_trace file.
-
- "preemptoff"
-
- Similar to irqsoff but traces and records the amount of
- time for which preemption is disabled.
-
- "preemptirqsoff"
-
- Similar to irqsoff and preemptoff, but traces and
- records the largest time for which irqs and/or preemption
- is disabled.
-
"wakeup"

Traces and records the max latency that it takes for
@@ -292,97 +266,6 @@ nice 19. The prio "140" is reserved for the idle task which is
the lowest priority thread (pid 0).

-Latency trace format
---------------------
-
-For traces that display latency times, the latency_trace file
-gives somewhat more information to see why a latency happened.
-Here is a typical trace.
-
-# tracer: irqsoff
-#
-irqsoff latency trace v1.1.5 on 2.6.26-rc8
---------------------------------------------------------------------
- latency: 97 us, #3/3, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2)
- -----------------
- | task: swapper-0 (uid:0 nice:0 policy:0 rt_prio:0)
- -----------------
- => started at: apic_timer_interrupt
- => ended at: do_softirq
-
-# _------=> CPU#
-# / _-----=> irqs-off
-# | / _----=> need-resched
-# || / _---=> hardirq/softirq
-# ||| / _--=> preempt-depth
-# |||| /
-# ||||| delay
-# cmd pid ||||| time | caller
-# \ / ||||| \ | /
- <idle>-0 0d..1 0us+: trace_hardirqs_off_thunk (apic_timer_interrupt)
- <idle>-0 0d.s. 97us : __do_softirq (do_softirq)
- <idle>-0 0d.s1 98us : trace_hardirqs_on (do_softirq)
-
-
-This shows that the current tracer is "irqsoff" tracing the time
-for which interrupts were disabled. It gives the trace version
-and the version of the kernel upon which this was executed on
-(2.6.26-rc8). Then it displays the max latency in microsecs (97
-us). The number of trace entries displayed and the total number
-recorded (both are three: #3/3). The type of preemption that was
-used (PREEMPT). VP, KP, SP, and HP are always zero and are
-reserved for later use. #P is the number of online CPUS (#P:2).
-
-The task is the process that was running when the latency
-occurred. (swapper pid: 0).
-
-The start and stop (the functions in which the interrupts were
-disabled and enabled respectively) that caused the latencies:
-
- apic_timer_interrupt is where the interrupts were disabled.
- do_softirq is where they were enabled again.
-
-The next lines after the header are the trace itself. The header
-explains which is which.
-
- cmd: The name of the process in the trace.
-
- pid: The PID of that process.
-
- CPU#: The CPU which the process was running on.
-
- irqs-off: 'd' interrupts are disabled. '.' otherwise.
- Note: If the architecture does not support a way to
- read the irq flags variable, an 'X' will always
- be printed here.
-
- need-resched: 'N' task need_resched is set, '.' otherwise.
-
- hardirq/softirq:
- 'H' - hard irq occurred inside a softirq.
- 'h' - hard irq is running
- 's' - soft irq is running
- '.' - normal context.
-
- preempt-depth: The level of preempt_disabled
-
-The above is mostly meaningful for kernel developers.
-
- time: This differs from the trace file output. The trace file output
- includes an absolute timestamp. The timestamp used by the
- latency_trace file is relative to the start of the trace.
-
- delay: This is just to help catch your eye a bit better. And
- needs to be fixed to be only relative to the same CPU.
- The marks are determined by the difference between this
- current trace and the next trace.
- '!' - greater than preempt_mark_thresh (default 100)
- '+' - greater than 1 microsecond
- ' ' - less than or equal to 1 microsecond.
-
- The rest is the same as the 'trace' file.
-
-
trace_options
-------------

@@ -556,413 +439,6 @@ functions that are within the trace. The descriptions of the
tracers will also show an example with ftrace enabled.

-irqsoff
--------
-
-When interrupts are disabled, the CPU can not react to any other
-external event (besides NMIs and SMIs). This prevents the timer
-interrupt from triggering or the mouse interrupt from letting
-the kernel know of a new mouse event. The result is a latency
-with the reaction time.
-
-The irqsoff tracer tracks the time for which interrupts are
-disabled. When a new maximum latency is hit, the tracer saves
-the trace leading up to that latency point so that every time a
-new maximum is reached, the old saved trace is discarded and the
-new trace is saved.
-
-To reset the maximum, echo 0 into tracing_max_latency. Here is
-an example:
-
- # echo irqsoff > /debug/tracing/current_tracer
- # echo 0 > /debug/tracing/tracing_max_latency
- # echo 1 > /debug/tracing/tracing_enabled
- # ls -ltr
- [...]
- # echo 0 > /debug/tracing/tracing_enabled
- # cat /debug/tracing/latency_trace
-# tracer: irqsoff
-#
-irqsoff latency trace v1.1.5 on 2.6.26
---------------------------------------------------------------------
- latency: 12 us, #3/3, CPU#1 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2)
- -----------------
- | task: bash-3730 (uid:0 nice:0 policy:0 rt_prio:0)
- -----------------
- => started at: sys_setpgid
- => ended at: sys_setpgid
-
-# _------=> CPU#
-# / _-----=> irqs-off
-# | / _----=> need-resched
-# || / _---=> hardirq/softirq
-# ||| / _--=> preempt-depth
-# |||| /
-# ||||| delay
-# cmd pid ||||| time | caller
-# \ / ||||| \ | /
- bash-3730 1d... 0us : _write_lock_irq (sys_setpgid)
- bash-3730 1d..1 1us+: _write_unlock_irq (sys_setpgid)
- bash-3730 1d..2 14us : trace_hardirqs_on (sys_setpgid)
-
-
-Here we see that that we had a latency of 12 microsecs (which is
-very good). The _write_lock_irq in sys_setpgid disabled
-interrupts. The difference between the 12 and the displayed
-timestamp 14us occurred because the clock was incremented
-between the time of recording the max latency and the time of
-recording the function that had that latency.
-
-Note the above example had ftrace_enabled not set. If we set the
-ftrace_enabled, we get a much larger output:
-
-# tracer: irqsoff
-#
-irqsoff latency trace v1.1.5 on 2.6.26-rc8
---------------------------------------------------------------------
- latency: 50 us, #101/101, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2)
- -----------------
- | task: ls-4339 (uid:0 nice:0 policy:0 rt_prio:0)
- -----------------
- => started at: __alloc_pages_internal
- => ended at: __alloc_pages_internal
-
-# _------=> CPU#
-# / _-----=> irqs-off
-# | / _----=> need-resched
-# || / _---=> hardirq/softirq
-# ||| / _--=> preempt-depth
-# |||| /
-# ||||| delay
-# cmd pid ||||| time | caller
-# \ / ||||| \ | /
- ls-4339 0...1 0us+: get_page_from_freelist (__alloc_pages_internal)
- ls-4339 0d..1 3us : rmqueue_bulk (get_page_from_freelist)
- ls-4339 0d..1 3us : _spin_lock (rmqueue_bulk)
- ls-4339 0d..1 4us : add_preempt_count (_spin_lock)
- ls-4339 0d..2 4us : __rmqueue (rmqueue_bulk)
- ls-4339 0d..2 5us : __rmqueue_smallest (__rmqueue)
- ls-4339 0d..2 5us : __mod_zone_page_state (__rmqueue_smallest)
- ls-4339 0d..2 6us : __rmqueue (rmqueue_bulk)
- ls-4339 0d..2 6us : __rmqueue_smallest (__rmqueue)
- ls-4339 0d..2 7us : __mod_zone_page_state (__rmqueue_smallest)
- ls-4339 0d..2 7us : __rmqueue (rmqueue_bulk)
- ls-4339 0d..2 8us : __rmqueue_smallest (__rmqueue)
-[...]
- ls-4339 0d..2 46us : __rmqueue_smallest (__rmqueue)
- ls-4339 0d..2 47us : __mod_zone_page_state (__rmqueue_smallest)
- ls-4339 0d..2 47us : __rmqueue (rmqueue_bulk)
- ls-4339 0d..2 48us : __rmqueue_smallest (__rmqueue)
- ls-4339 0d..2 48us : __mod_zone_page_state (__rmqueue_smallest)
- ls-4339 0d..2 49us : _spin_unlock (rmqueue_bulk)
- ls-4339 0d..2 49us : sub_preempt_count (_spin_unlock)
- ls-4339 0d..1 50us : get_page_from_freelist (__alloc_pages_internal)
- ls-4339 0d..2 51us : trace_hardirqs_on (__alloc_pages_internal)
-
-
-
-Here we traced a 50 microsecond latency. But we also see all the
-functions that were called during that time. Note that by
-enabling function tracing, we incur an added overhead. This
-overhead may extend the latency times. But nevertheless, this
-trace has provided some very helpful debugging information.
-
-
-preemptoff
-----------
-
-When preemption is disabled, we may be able to receive
-interrupts but the task cannot be preempted and a higher
-priority task must wait for preemption to be enabled again
-before it can preempt a lower priority task.
-
-The preemptoff tracer traces the places that disable preemption.
-Like the irqsoff tracer, it records the maximum latency for
-which preemption was disabled. The control of preemptoff tracer
-is much like the irqsoff tracer.
-
- # echo preemptoff > /debug/tracing/current_tracer
- # echo 0 > /debug/tracing/tracing_max_latency
- # echo 1 > /debug/tracing/tracing_enabled
- # ls -ltr
- [...]
- # echo 0 > /debug/tracing/tracing_enabled
- # cat /debug/tracing/latency_trace
-# tracer: preemptoff
-#
-preemptoff latency trace v1.1.5 on 2.6.26-rc8
---------------------------------------------------------------------
- latency: 29 us, #3/3, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2)
- -----------------
- | task: sshd-4261 (uid:0 nice:0 policy:0 rt_prio:0)
- -----------------
- => started at: do_IRQ
- => ended at: __do_softirq
-
-# _------=> CPU#
-# / _-----=> irqs-off
-# | / _----=> need-resched
-# || / _---=> hardirq/softirq
-# ||| / _--=> preempt-depth
-# |||| /
-# ||||| delay
-# cmd pid ||||| time | caller
-# \ / ||||| \ | /
- sshd-4261 0d.h. 0us+: irq_enter (do_IRQ)
- sshd-4261 0d.s. 29us : _local_bh_enable (__do_softirq)
- sshd-4261 0d.s1 30us : trace_preempt_on (__do_softirq)
-
-
-This has some more changes. Preemption was disabled when an
-interrupt came in (notice the 'h'), and was enabled while doing
-a softirq. (notice the 's'). But we also see that interrupts
-have been disabled when entering the preempt off section and
-leaving it (the 'd'). We do not know if interrupts were enabled
-in the mean time.
-
-# tracer: preemptoff
-#
-preemptoff latency trace v1.1.5 on 2.6.26-rc8
---------------------------------------------------------------------
- latency: 63 us, #87/87, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2)
- -----------------
- | task: sshd-4261 (uid:0 nice:0 policy:0 rt_prio:0)
- -----------------
- => started at: remove_wait_queue
- => ended at: __do_softirq
-
-# _------=> CPU#
-# / _-----=> irqs-off
-# | / _----=> need-resched
-# || / _---=> hardirq/softirq
-# ||| / _--=> preempt-depth
-# |||| /
-# ||||| delay
-# cmd pid ||||| time | caller
-# \ / ||||| \ | /
- sshd-4261 0d..1 0us : _spin_lock_irqsave (remove_wait_queue)
- sshd-4261 0d..1 1us : _spin_unlock_irqrestore (remove_wait_queue)
- sshd-4261 0d..1 2us : do_IRQ (common_interrupt)
- sshd-4261 0d..1 2us : irq_enter (do_IRQ)
- sshd-4261 0d..1 2us : idle_cpu (irq_enter)
- sshd-4261 0d..1 3us : add_preempt_count (irq_enter)
- sshd-4261 0d.h1 3us : idle_cpu (irq_enter)
- sshd-4261 0d.h. 4us : handle_fasteoi_irq (do_IRQ)
-[...]
- sshd-4261 0d.h. 12us : add_preempt_count (_spin_lock)
- sshd-4261 0d.h1 12us : ack_ioapic_quirk_irq (handle_fasteoi_irq)
- sshd-4261 0d.h1 13us : move_native_irq (ack_ioapic_quirk_irq)
- sshd-4261 0d.h1 13us : _spin_unlock (handle_fasteoi_irq)
- sshd-4261 0d.h1 14us : sub_preempt_count (_spin_unlock)
- sshd-4261 0d.h1 14us : irq_exit (do_IRQ)
- sshd-4261 0d.h1 15us : sub_preempt_count (irq_exit)
- sshd-4261 0d..2 15us : do_softirq (irq_exit)
- sshd-4261 0d... 15us : __do_softirq (do_softirq)
- sshd-4261 0d... 16us : __local_bh_disable (__do_softirq)
- sshd-4261 0d... 16us+: add_preempt_count (__local_bh_disable)
- sshd-4261 0d.s4 20us : add_preempt_count (__local_bh_disable)
- sshd-4261 0d.s4 21us : sub_preempt_count (local_bh_enable)
- sshd-4261 0d.s5 21us : sub_preempt_count (local_bh_enable)
-[...]
- sshd-4261 0d.s6 41us : add_preempt_count (__local_bh_disable)
- sshd-4261 0d.s6 42us : sub_preempt_count (local_bh_enable)
- sshd-4261 0d.s7 42us : sub_preempt_count (local_bh_enable)
- sshd-4261 0d.s5 43us : add_preempt_count (__local_bh_disable)
- sshd-4261 0d.s5 43us : sub_preempt_count (local_bh_enable_ip)
- sshd-4261 0d.s6 44us : sub_preempt_count (local_bh_enable_ip)
- sshd-4261 0d.s5 44us : add_preempt_count (__local_bh_disable)
- sshd-4261 0d.s5 45us : sub_preempt_count (local_bh_enable)
-[...]
- sshd-4261 0d.s. 63us : _local_bh_enable (__do_softirq)
- sshd-4261 0d.s1 64us : trace_preempt_on (__do_softirq)
-
-
-The above is an example of the preemptoff trace with
-ftrace_enabled set. Here we see that interrupts were disabled
-the entire time. The irq_enter code lets us know that we entered
-an interrupt 'h'. Before that, the functions being traced still
-show that it is not in an interrupt, but we can see from the
-functions themselves that this is not the case.
-
-Notice that __do_softirq when called does not have a
-preempt_count. It may seem that we missed a preempt enabling.
-What really happened is that the preempt count is held on the
-thread's stack and we switched to the softirq stack (4K stacks
-in effect). The code does not copy the preempt count, but
-because interrupts are disabled, we do not need to worry about
-it. Having a tracer like this is good for letting people know
-what really happens inside the kernel.
-
-
-preemptirqsoff
---------------
-
-Knowing the locations that have interrupts disabled or
-preemption disabled for the longest times is helpful. But
-sometimes we would like to know when either preemption and/or
-interrupts are disabled.
-
-Consider the following code:
-
- local_irq_disable();
- call_function_with_irqs_off();
- preempt_disable();
- call_function_with_irqs_and_preemption_off();
- local_irq_enable();
- call_function_with_preemption_off();
- preempt_enable();
-
-The irqsoff tracer will record the total length of
-call_function_with_irqs_off() and
-call_function_with_irqs_and_preemption_off().
-
-The preemptoff tracer will record the total length of
-call_function_with_irqs_and_preemption_off() and
-call_function_with_preemption_off().
-
-But neither will trace the time that interrupts and/or
-preemption is disabled. This total time is the time that we can
-not schedule. To record this time, use the preemptirqsoff
-tracer.
-
-Again, using this trace is much like the irqsoff and preemptoff
-tracers.
-
- # echo preemptirqsoff > /debug/tracing/current_tracer
- # echo 0 > /debug/tracing/tracing_max_latency
- # echo 1 > /debug/tracing/tracing_enabled
- # ls -ltr
- [...]
- # echo 0 > /debug/tracing/tracing_enabled
- # cat /debug/tracing/latency_trace
-# tracer: preemptirqsoff
-#
-preemptirqsoff latency trace v1.1.5 on 2.6.26-rc8
---------------------------------------------------------------------
- latency: 293 us, #3/3, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2)
- -----------------
- | task: ls-4860 (uid:0 nice:0 policy:0 rt_prio:0)
- -----------------
- => started at: apic_timer_interrupt
- => ended at: __do_softirq
-
-# _------=> CPU#
-# / _-----=> irqs-off
-# | / _----=> need-resched
-# || / _---=> hardirq/softirq
-# ||| / _--=> preempt-depth
-# |||| /
-# ||||| delay
-# cmd pid ||||| time | caller
-# \ / ||||| \ | /
- ls-4860 0d... 0us!: trace_hardirqs_off_thunk (apic_timer_interrupt)
- ls-4860 0d.s. 294us : _local_bh_enable (__do_softirq)
- ls-4860 0d.s1 294us : trace_preempt_on (__do_softirq)
-
-
-
-The trace_hardirqs_off_thunk is called from assembly on x86 when
-interrupts are disabled in the assembly code. Without the
-function tracing, we do not know if interrupts were enabled
-within the preemption points. We do see that it started with
-preemption enabled.
-
-Here is a trace with ftrace_enabled set:
-
-
-# tracer: preemptirqsoff
-#
-preemptirqsoff latency trace v1.1.5 on 2.6.26-rc8
---------------------------------------------------------------------
- latency: 105 us, #183/183, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2)
- -----------------
- | task: sshd-4261 (uid:0 nice:0 policy:0 rt_prio:0)
- -----------------
- => started at: write_chan
- => ended at: __do_softirq
-
-# _------=> CPU#
-# / _-----=> irqs-off
-# | / _----=> need-resched
-# || / _---=> hardirq/softirq
-# ||| / _--=> preempt-depth
-# |||| /
-# ||||| delay
-# cmd pid ||||| time | caller
-# \ / ||||| \ | /
- ls-4473 0.N.. 0us : preempt_schedule (write_chan)
- ls-4473 0dN.1 1us : _spin_lock (schedule)
- ls-4473 0dN.1 2us : add_preempt_count (_spin_lock)
- ls-4473 0d..2 2us : put_prev_task_fair (schedule)
-[...]
- ls-4473 0d..2 13us : set_normalized_timespec (ktime_get_ts)
- ls-4473 0d..2 13us : __switch_to (schedule)
- sshd-4261 0d..2 14us : finish_task_switch (schedule)
- sshd-4261 0d..2 14us : _spin_unlock_irq (finish_task_switch)
- sshd-4261 0d..1 15us : add_preempt_count (_spin_lock_irqsave)
- sshd-4261 0d..2 16us : _spin_unlock_irqrestore (hrtick_set)
- sshd-4261 0d..2 16us : do_IRQ (common_interrupt)
- sshd-4261 0d..2 17us : irq_enter (do_IRQ)
- sshd-4261 0d..2 17us : idle_cpu (irq_enter)
- sshd-4261 0d..2 18us : add_preempt_count (irq_enter)
- sshd-4261 0d.h2 18us : idle_cpu (irq_enter)
- sshd-4261 0d.h. 18us : handle_fasteoi_irq (do_IRQ)
- sshd-4261 0d.h. 19us : _spin_lock (handle_fasteoi_irq)
- sshd-4261 0d.h. 19us : add_preempt_count (_spin_lock)
- sshd-4261 0d.h1 20us : _spin_unlock (handle_fasteoi_irq)
- sshd-4261 0d.h1 20us : sub_preempt_count (_spin_unlock)
-[...]
- sshd-4261 0d.h1 28us : _spin_unlock (handle_fasteoi_irq)
- sshd-4261 0d.h1 29us : sub_preempt_count (_spin_unlock)
- sshd-4261 0d.h2 29us : irq_exit (do_IRQ)
- sshd-4261 0d.h2 29us : sub_preempt_count (irq_exit)
- sshd-4261 0d..3 30us : do_softirq (irq_exit)
- sshd-4261 0d... 30us : __do_softirq (do_softirq)
- sshd-4261 0d... 31us : __local_bh_disable (__do_softirq)
- sshd-4261 0d... 31us+: add_preempt_count (__local_bh_disable)
- sshd-4261 0d.s4 34us : add_preempt_count (__local_bh_disable)
-[...]
- sshd-4261 0d.s3 43us : sub_preempt_count (local_bh_enable_ip)
- sshd-4261 0d.s4 44us : sub_preempt_count (local_bh_enable_ip)
- sshd-4261 0d.s3 44us : smp_apic_timer_interrupt (apic_timer_interrupt)
- sshd-4261 0d.s3 45us : irq_enter (smp_apic_timer_interrupt)
- sshd-4261 0d.s3 45us : idle_cpu (irq_enter)
- sshd-4261 0d.s3 46us : add_preempt_count (irq_enter)
- sshd-4261 0d.H3 46us : idle_cpu (irq_enter)
- sshd-4261 0d.H3 47us : hrtimer_interrupt (smp_apic_timer_interrupt)
- sshd-4261 0d.H3 47us : ktime_get (hrtimer_interrupt)
-[...]
- sshd-4261 0d.H3 81us : tick_program_event (hrtimer_interrupt)
- sshd-4261 0d.H3 82us : ktime_get (tick_program_event)
- sshd-4261 0d.H3 82us : ktime_get_ts (ktime_get)
- sshd-4261 0d.H3 83us : getnstimeofday (ktime_get_ts)
- sshd-4261 0d.H3 83us : set_normalized_timespec (ktime_get_ts)
- sshd-4261 0d.H3 84us : clockevents_program_event (tick_program_event)
- sshd-4261 0d.H3 84us : lapic_next_event (clockevents_program_event)
- sshd-4261 0d.H3 85us : irq_exit (smp_apic_timer_interrupt)
- sshd-4261 0d.H3 85us : sub_preempt_count (irq_exit)
- sshd-4261 0d.s4 86us : sub_preempt_count (irq_exit)
- sshd-4261 0d.s3 86us : add_preempt_count (__local_bh_disable)
-[...]
- sshd-4261 0d.s1 98us : sub_preempt_count (net_rx_action)
- sshd-4261 0d.s. 99us : add_preempt_count (_spin_lock_irq)
- sshd-4261 0d.s1 99us+: _spin_unlock_irq (run_timer_softirq)
- sshd-4261 0d.s. 104us : _local_bh_enable (__do_softirq)
- sshd-4261 0d.s. 104us : sub_preempt_count (_local_bh_enable)
- sshd-4261 0d.s. 105us : _local_bh_enable (__do_softirq)
- sshd-4261 0d.s1 105us : trace_preempt_on (__do_softirq)
-
-
-This is a very interesting trace. It started with the preemption
-of the ls task. We see that the task had the "need_resched" bit
-set via the 'N' in the trace. Interrupts were disabled before
-the spin_lock at the beginning of the trace. We see that a
-schedule took place to run sshd. When the interrupts were
-enabled, we took an interrupt. On return from the interrupt
-handler, the softirq ran. We took another interrupt while
-running the softirq as we see from the capital 'H'.
-
-
wakeup
------

--
1.6.0.6