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Message-ID: <20090307153427.GA6075@nowhere> Date: Sat, 7 Mar 2009 16:34:28 +0100 From: Frederic Weisbecker <fweisbec@...il.com> To: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> Cc: Ingo Molnar <mingo@...e.hu>, Steven Rostedt <srostedt@...hat.com>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH for tip] ftrace: remove latency_trace document On Sat, Mar 07, 2009 at 11:53:40PM +0900, KOSAKI Motohiro wrote: > 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@...fujitsu.com> > --- Hi, The latency_trace file has been removed but the latency tracing stil exists. It has become an option instead of a file now: echo latency-format > /debugfs/tracing/trace_options There are even some tracers that default enable it (irqsoff, preemptoff...) IMO, the documentation about latency tracing shouldn't be removed but just updated a bit to reflect this change. Frederic. > 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 > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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