***** TRACEFS-TRACING-IRQFLAGS.txt *****

[ HELP ]

[1] tracing mini-HOWTO: See /sys/kernel/tracing/README file
[2] http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/irqflags-tracing.txt
[3] http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/trace

[ KERNEL-CONFIG SETTINGS ]

[ TRACEFS ]
CONFIG_TRACING_SUPPORT=y
CONFIG_TRACING=y

[ IRQFLAGS-TRACING AND IRQSOFF LATENCY TRACER ]
CONFIG_TRACE_IRQFLAGS_SUPPORT=y
CONFIG_TRACE_IRQFLAGS=y
CONFIG_IRQSOFF_TRACER=y

[ MOUNT AND CHECK TRACEFS ]

root# mount -t tracefs none /sys/kernel/tracing

root# mount | grep tracefs
none on /sys/kernel/tracing type tracefs (rw,relatime)

[ ENTER TRACEFS-DIR ]

root# cd /sys/kernel/tracing/

[ DOCUMENTATION: TRACING MINI-HOWTO ]

root# cat README

[ CHECK TRACING SETTINGS ]

root# cat tracing_on
1

[ DISABLE TRACING AND EMPTY TRACE FILE ]

root# echo 0 > tracing_on
root# cat tracing_on
0

root# echo > trace
root# cat trace
# tracer: nop
#
# entries-in-buffer/entries-written: 0/0   #P:4
#
#                              _-----=> irqs-off
#                             / _----=> need-resched
#                            | / _---=> hardirq/softirq
#                            || / _--=> preempt-depth
#                            ||| /     delay
#           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
#              | |       |   ||||       |         |

[ CHECK AVAILABLE TRACERS AND EVENTS (HERE: IRQSOFF) ]

root# cat /sys/kernel/tracing/available_tracers
blk mmiotrace function_graph wakeup_dl wakeup_rt wakeup irqsoff function nop <--- XXX: IRQSOFF

root# cat /sys/kernel/tracing/available_events | grep irq:
irq:irq_handler_entry
irq:irq_handler_exit
irq:softirq_entry
irq:softirq_exit
irq:softirq_raise

root# cat events/irq/enable
1

root# cat events/irq/filter
### global filter ###
# Use this to set filters for multiple events.
# Only events with the given fields will be affected.
# If no events are modified, an error message will be displayed here

[ ENABLE IRQ_HANDLER AND SOFTIRQ SETTINGS ]

root# echo 1 > events/irq/irq_handler_entry/enable
root# echo 1 > events/irq/irq_handler_exit/enable
root# cat events/irq/irq_handler_entry/enable events/irq/irq_handler_exit/enable
1
1

root# echo 1 > events/irq/softirq_entry/enable
root# echo 1 > events/irq/softirq_exit/enable
root# echo 1 > events/irq/softirq_raise/enable
root# cat events/irq/softirq_entry/enable events/irq/softirq_exit/enable events/irq/softirq_raise/enable
1
1
1

root# cat trace
# tracer: nop
#
# entries-in-buffer/entries-written: 0/0   #P:4
#
#                              _-----=> irqs-off
#                             / _----=> need-resched
#                            | / _---=> hardirq/softirq
#                            || / _--=> preempt-depth
#                            ||| /     delay
#           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
#              | |       |   ||||       |         |

[ START TRACING ]

root# echo 1 > tracing_on

[ CHECK TRACE FILE ]

root# cat trace


-dileks // 27-SEP-2015