# SPDX-License-Identifier: GPL-2.0-only## Architectures that offer an FUNCTION_TRACER implementation should# select HAVE_FUNCTION_TRACER:# config USER_STACKTRACE_SUPPORT bool config NOP_TRACER bool config HAVE_RETHOOK bool config RETHOOK bool depends on HAVE_RETHOOK help Enable generic return hooking feature. This is an internal API, which will be used by other function-entry hooking features like fprobe and kprobes. config HAVE_FUNCTION_TRACER bool help See Documentation/trace/ftrace-design.rst config HAVE_FUNCTION_GRAPH_TRACER bool help See Documentation/trace/ftrace-design.rst config HAVE_FUNCTION_GRAPH_RETVAL bool config HAVE_DYNAMIC_FTRACE bool help See Documentation/trace/ftrace-design.rst config HAVE_DYNAMIC_FTRACE_WITH_REGS bool config HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS bool config HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS bool config HAVE_DYNAMIC_FTRACE_WITH_ARGS bool help If this is set, then arguments and stack can be found from the ftrace_regs passed into the function callback regs parameter by default, even without setting the REGS flag in the ftrace_ops. This allows for use of ftrace_regs_get_argument() and ftrace_regs_get_stack_pointer(). config HAVE_DYNAMIC_FTRACE_NO_PATCHABLE bool help If the architecture generates __patchable_function_entries sections but does not want them included in the ftrace locations. config HAVE_FTRACE_MCOUNT_RECORD bool help See Documentation/trace/ftrace-design.rst config HAVE_SYSCALL_TRACEPOINTS bool help See Documentation/trace/ftrace-design.rst config HAVE_FENTRY bool help Arch supports the gcc options -pg with -mfentry config HAVE_NOP_MCOUNT bool help Arch supports the gcc options -pg with -mrecord-mcount and -nop-mcount config HAVE_OBJTOOL_MCOUNT bool help Arch supports objtool --mcount config HAVE_OBJTOOL_NOP_MCOUNT bool help Arch supports the objtool options --mcount with --mnop. An architecture can select this if it wants to enable nop'ing of ftrace locations. config HAVE_C_RECORDMCOUNT bool help C version of recordmcount available? config HAVE_BUILDTIME_MCOUNT_SORT bool help An architecture selects this if it sorts the mcount_loc section at build time. config BUILDTIME_MCOUNT_SORT bool default y depends on HAVE_BUILDTIME_MCOUNT_SORT && DYNAMIC_FTRACE help Sort the mcount_loc section at build time. config TRACER_MAX_TRACE bool config TRACE_CLOCK bool config RING_BUFFER bool select TRACE_CLOCK select IRQ_WORK config EVENT_TRACING select CONTEXT_SWITCH_TRACER select GLOB bool config CONTEXT_SWITCH_TRACER bool config RING_BUFFER_ALLOW_SWAP bool help Allow the use of ring_buffer_swap_cpu. Adds a very slight overhead to tracing when enabled. config PREEMPTIRQ_TRACEPOINTS bool depends on TRACE_PREEMPT_TOGGLE || TRACE_IRQFLAGS select TRACING default y help Create preempt/irq toggle tracepoints if needed, so that other parts of the kernel can use them to generate or add hooks to them. # All tracer options should select GENERIC_TRACER. For those options that are# enabled by all tracers (context switch and event tracer) they select TRACING.# This allows those options to appear when no other tracer is selected. But the# options do not appear when something else selects it. We need the two options# GENERIC_TRACER and TRACING to avoid circular dependencies to accomplish the# hiding of the automatic options. config TRACING bool select RING_BUFFER select STACKTRACE if STACKTRACE_SUPPORT select TRACEPOINTS select NOP_TRACER select BINARY_PRINTF select EVENT_TRACING select TRACE_CLOCK select NEED_TASKS_RCU config GENERIC_TRACER bool select TRACING ## Minimum requirements an architecture has to meet for us to# be able to offer generic tracing facilities:#config TRACING_SUPPORT bool depends on TRACE_IRQFLAGS_SUPPORT depends on STACKTRACE_SUPPORT default y menuconfig FTRACE bool "Tracers" depends on TRACING_SUPPORT default y if DEBUG_KERNEL help Enable the kernel tracing infrastructure. if FTRACE config BOOTTIME_TRACING bool "Boot-time Tracing support" depends on TRACING select BOOT_CONFIG help Enable developer to setup ftrace subsystem via supplemental kernel cmdline at boot time for debugging (tracing) driver initialization and boot process. config FUNCTION_TRACER bool "Kernel Function Tracer" depends on HAVE_FUNCTION_TRACER select KALLSYMS select GENERIC_TRACER select CONTEXT_SWITCH_TRACER select GLOB select NEED_TASKS_RCU select TASKS_RUDE_RCU help Enable the kernel to trace every kernel function. This is done by using a compiler feature to insert a small, 5-byte No-Operation instruction at the beginning of every kernel function, which NOP sequence is then dynamically patched into a tracer call when tracing is enabled by the administrator. If it's runtime disabled (the bootup default), then the overhead of the instructions is very small and not measurable even in micro-benchmarks (at least on x86, but may have impact on other architectures). config FUNCTION_GRAPH_TRACER bool "Kernel Function Graph Tracer" depends on HAVE_FUNCTION_GRAPH_TRACER depends on FUNCTION_TRACER depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE default y help Enable the kernel to trace a function at both its return and its entry. Its first purpose is to trace the duration of functions and draw a call graph for each thread with some information like the return value. This is done by setting the current return address on the current task structure into a stack of calls. config FUNCTION_GRAPH_RETVAL bool "Kernel Function Graph Return Value" depends on HAVE_FUNCTION_GRAPH_RETVAL depends on FUNCTION_GRAPH_TRACER default n help Support recording and printing the function return value when using function graph tracer. It can be helpful to locate functions that return errors. This feature is off by default, and you can enable it via the trace option funcgraph-retval. See Documentation/trace/ftrace.rst config FUNCTION_GRAPH_RETADDR bool "Kernel Function Graph Return Address" depends on FUNCTION_GRAPH_TRACER default n help Support recording and printing the function return address when using function graph tracer. It can be helpful to locate code line that the function is called. This feature is off by default, and you can enable it via the trace option funcgraph-retaddr. config DYNAMIC_FTRACE bool "enable/disable function tracing dynamically" depends on FUNCTION_TRACER depends on HAVE_DYNAMIC_FTRACE default y help This option will modify all the calls to function tracing dynamically (will patch them out of the binary image and replace them with a No-Op instruction) on boot up. During compile time, a table is made of all the locations that ftrace can function trace, and this table is linked into the kernel image. When this is enabled, functions can be individually enabled, and the functions not enabled will not affect performance of the system. See the files in /sys/kernel/tracing: available_filter_functions set_ftrace_filter set_ftrace_notrace This way a CONFIG_FUNCTION_TRACER kernel is slightly larger, but otherwise has native performance as long as no tracing is active. config DYNAMIC_FTRACE_WITH_REGS def_bool y depends on DYNAMIC_FTRACE depends on HAVE_DYNAMIC_FTRACE_WITH_REGS config DYNAMIC_FTRACE_WITH_DIRECT_CALLS def_bool y depends on DYNAMIC_FTRACE_WITH_REGS || DYNAMIC_FTRACE_WITH_ARGS depends on HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS config DYNAMIC_FTRACE_WITH_CALL_OPS def_bool y depends on HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS config DYNAMIC_FTRACE_WITH_ARGS def_bool y depends on DYNAMIC_FTRACE depends on HAVE_DYNAMIC_FTRACE_WITH_ARGS config FPROBE bool "Kernel Function Probe (fprobe)" depends on FUNCTION_TRACER depends on DYNAMIC_FTRACE_WITH_REGS depends on HAVE_RETHOOK select RETHOOK default n help This option enables kernel function probe (fprobe) based on ftrace. The fprobe is similar to kprobes, but probes only for kernel function entries and exits. This also can probe multiple functions by one fprobe. If unsure, say N. config FUNCTION_PROFILER bool "Kernel function profiler" depends on FUNCTION_TRACER default n help This option enables the kernel function profiler. A file is created in debugfs called function_profile_enabled which defaults to zero. When a 1 is echoed into this file profiling begins, and when a zero is entered, profiling stops. A "functions" file is created in the trace_stat directory; this file shows the list of functions that have been hit and their counters. If in doubt, say N. config STACK_TRACER bool "Trace max stack" depends on HAVE_FUNCTION_TRACER select FUNCTION_TRACER select STACKTRACE select KALLSYMS help This special tracer records the maximum stack footprint of the kernel and displays it in /sys/kernel/tracing/stack_trace. This tracer works by hooking into every function call that the kernel executes, and keeping a maximum stack depth value and stack-trace saved. If this is configured with DYNAMIC_FTRACE then it will not have any overhead while the stack tracer is disabled. To enable the stack tracer on bootup, pass in 'stacktrace' on the kernel command line. The stack tracer can also be enabled or disabled via the sysctl kernel.stack_tracer_enabled Say N if unsure. config TRACE_PREEMPT_TOGGLE bool help Enables hooks which will be called when preemption is first disabled, and last enabled. config IRQSOFF_TRACER bool "Interrupts-off Latency Tracer" default n depends on TRACE_IRQFLAGS_SUPPORT select TRACE_IRQFLAGS select GENERIC_TRACER select TRACER_MAX_TRACE select RING_BUFFER_ALLOW_SWAP select TRACER_SNAPSHOT select TRACER_SNAPSHOT_PER_CPU_SWAP help This option measures the time spent in irqs-off critical sections, with microsecond accuracy. The default measurement method is a maximum search, which is disabled by default and can be runtime (re-)started via: echo 0 > /sys/kernel/tracing/tracing_max_latency (Note that kernel size and overhead increase with this option enabled. This option and the preempt-off timing option can be used together or separately.) config PREEMPT_TRACER bool "Preemption-off Latency Tracer" default n depends on PREEMPTION select GENERIC_TRACER select TRACER_MAX_TRACE select RING_BUFFER_ALLOW_SWAP select TRACER_SNAPSHOT select TRACER_SNAPSHOT_PER_CPU_SWAP select TRACE_PREEMPT_TOGGLE help This option measures the time spent in preemption-off critical sections, with microsecond accuracy. The default measurement method is a maximum search, which is disabled by default and can be runtime (re-)started via: echo 0 > /sys/kernel/tracing/tracing_max_latency (Note that kernel size and overhead increase with this option enabled. This option and the irqs-off timing option can be used together or separately.) config SCHED_TRACER bool "Scheduling Latency Tracer" select GENERIC_TRACER select CONTEXT_SWITCH_TRACER select TRACER_MAX_TRACE select TRACER_SNAPSHOT help This tracer tracks the latency of the highest priority task to be scheduled in, starting from the point it has woken up. config HWLAT_TRACER bool "Tracer to detect hardware latencies (like SMIs)" select GENERIC_TRACER select TRACER_MAX_TRACE help This tracer, when enabled will create one or more kernel threads, depending on what the cpumask file is set to, which each thread spinning in a loop looking for interruptions caused by something other than the kernel. For example, if a System Management Interrupt (SMI) takes a noticeable amount of time, this tracer will detect it. This is useful for testing if a system is reliable for Real Time tasks. Some files are created in the tracing directory when this is enabled: hwlat_detector/width - time in usecs for how long to spin for hwlat_detector/window - time in usecs between the start of each iteration A kernel thread is created that will spin with interrupts disabled for "width" microseconds in every "window" cycle. It will not spin for "window - width" microseconds, where the system can continue to operate. The output will appear in the trace and trace_pipe files. When the tracer is not running, it has no affect on the system, but when it is running, it can cause the system to be periodically non responsive. Do not run this tracer on a production system. To enable this tracer, echo in "hwlat" into the current_tracer file. Every time a latency is greater than tracing_thresh, it will be recorded into the ring buffer. config OSNOISE_TRACER bool "OS Noise tracer" select GENERIC_TRACER select TRACER_MAX_TRACE help In the context of high-performance computing (HPC), the Operating System Noise (osnoise) refers to the interference experienced by an application due to activities inside the operating system. In the context of Linux, NMIs, IRQs, SoftIRQs, and any other system thread can cause noise to the system. Moreover, hardware-related jobs can also cause noise, for example, via SMIs. The osnoise tracer leverages the hwlat_detector by running a similar loop with preemption, SoftIRQs and IRQs enabled, thus allowing all the sources of osnoise during its execution. The osnoise tracer takes note of the entry and exit point of any source of interferences, increasing a per-cpu interference counter. It saves an interference counter for each source of interference. The interference counter for NMI, IRQs, SoftIRQs, and threads is increased anytime the tool observes these interferences' entry events. When a noise happens without any interference from the operating system level, the hardware noise counter increases, pointing to a hardware-related noise. In this way, osnoise can account for any source of interference. At the end of the period, the osnoise tracer prints the sum of all noise, the max single noise, the percentage of CPU available for the thread, and the counters for the noise sources. In addition to the tracer, a set of tracepoints were added to facilitate the identification of the osnoise source. The output will appear in the trace and trace_pipe files. To enable this tracer, echo in "osnoise" into the current_tracer file. config TIMERLAT_TRACER bool "Timerlat tracer" select OSNOISE_TRACER select GENERIC_TRACER help The timerlat tracer aims to help the preemptive kernel developers to find sources of wakeup latencies of real-time threads. The tracer creates a per-cpu kernel thread with real-time priority. The tracer thread sets a periodic timer to wakeup itself, and goes to sleep waiting for the timer to fire. At the wakeup, the thread then computes a wakeup latency value as the difference between the current time and the absolute time that the timer was set to expire. The tracer prints two lines at every activation. The first is theLines 1–500 of 1197. Load more
# SPDX-License-Identifier: GPL-2.0-only # # Architectures that offer an FUNCTION_TRACER implementation should # select HAVE_FUNCTION_TRACER: # config USER_STACKTRACE_SUPPORT bool config NOP_TRACER bool config HAVE_RETHOOK bool config RETHOOK bool depends on HAVE_RETHOOK help Enable generic return hooking feature. This is an internal API, which will be used by other function-entry hooking features like fprobe and kprobes. config HAVE_FUNCTION_TRACER bool help See Documentation/trace/ftrace-design.rst config HAVE_FUNCTION_GRAPH_TRACER bool help See Documentation/trace/ftrace-design.rst config HAVE_FUNCTION_GRAPH_RETVAL bool config HAVE_DYNAMIC_FTRACE bool help See Documentation/trace/ftrace-design.rst config HAVE_DYNAMIC_FTRACE_WITH_REGS bool config HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS bool config HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS bool config HAVE_DYNAMIC_FTRACE_WITH_ARGS bool help If this is set, then arguments and stack can be found from the ftrace_regs passed into the function callback regs parameter by default, even without setting the REGS flag in the ftrace_ops. This allows for use of ftrace_regs_get_argument() and ftrace_regs_get_stack_pointer(). config HAVE_DYNAMIC_FTRACE_NO_PATCHABLE bool help If the architecture generates __patchable_function_entries sections but does not want them included in the ftrace locations. config HAVE_FTRACE_MCOUNT_RECORD bool help See Documentation/trace/ftrace-design.rst config HAVE_SYSCALL_TRACEPOINTS bool help See Documentation/trace/ftrace-design.rst config HAVE_FENTRY bool help Arch supports the gcc options -pg with -mfentry config HAVE_NOP_MCOUNT bool help Arch supports the gcc options -pg with -mrecord-mcount and -nop-mcount config HAVE_OBJTOOL_MCOUNT bool help Arch supports objtool --mcount config HAVE_OBJTOOL_NOP_MCOUNT bool help Arch supports the objtool options --mcount with --mnop. An architecture can select this if it wants to enable nop'ing of ftrace locations. config HAVE_C_RECORDMCOUNT bool help C version of recordmcount available? config HAVE_BUILDTIME_MCOUNT_SORT bool help An architecture selects this if it sorts the mcount_loc section at build time. config BUILDTIME_MCOUNT_SORT bool default y depends on HAVE_BUILDTIME_MCOUNT_SORT && DYNAMIC_FTRACE help Sort the mcount_loc section at build time. config TRACER_MAX_TRACE bool config TRACE_CLOCK bool config RING_BUFFER bool select TRACE_CLOCK select IRQ_WORK config EVENT_TRACING select CONTEXT_SWITCH_TRACER select GLOB bool config CONTEXT_SWITCH_TRACER bool config RING_BUFFER_ALLOW_SWAP bool help Allow the use of ring_buffer_swap_cpu. Adds a very slight overhead to tracing when enabled. config PREEMPTIRQ_TRACEPOINTS bool depends on TRACE_PREEMPT_TOGGLE || TRACE_IRQFLAGS select TRACING default y help Create preempt/irq toggle tracepoints if needed, so that other parts of the kernel can use them to generate or add hooks to them. # All tracer options should select GENERIC_TRACER. For those options that are # enabled by all tracers (context switch and event tracer) they select TRACING. # This allows those options to appear when no other tracer is selected. But the # options do not appear when something else selects it. We need the two options # GENERIC_TRACER and TRACING to avoid circular dependencies to accomplish the # hiding of the automatic options. config TRACING bool select RING_BUFFER select STACKTRACE if STACKTRACE_SUPPORT select TRACEPOINTS select NOP_TRACER select BINARY_PRINTF select EVENT_TRACING select TRACE_CLOCK select NEED_TASKS_RCU config GENERIC_TRACER bool select TRACING # # Minimum requirements an architecture has to meet for us to # be able to offer generic tracing facilities: # config TRACING_SUPPORT bool depends on TRACE_IRQFLAGS_SUPPORT depends on STACKTRACE_SUPPORT default y menuconfig FTRACE bool "Tracers" depends on TRACING_SUPPORT default y if DEBUG_KERNEL help Enable the kernel tracing infrastructure. if FTRACE config BOOTTIME_TRACING bool "Boot-time Tracing support" depends on TRACING select BOOT_CONFIG help Enable developer to setup ftrace subsystem via supplemental kernel cmdline at boot time for debugging (tracing) driver initialization and boot process. config FUNCTION_TRACER bool "Kernel Function Tracer" depends on HAVE_FUNCTION_TRACER select KALLSYMS select GENERIC_TRACER select CONTEXT_SWITCH_TRACER select GLOB select NEED_TASKS_RCU select TASKS_RUDE_RCU help Enable the kernel to trace every kernel function. This is done by using a compiler feature to insert a small, 5-byte No-Operation instruction at the beginning of every kernel function, which NOP sequence is then dynamically patched into a tracer call when tracing is enabled by the administrator. If it's runtime disabled (the bootup default), then the overhead of the instructions is very small and not measurable even in micro-benchmarks (at least on x86, but may have impact on other architectures). config FUNCTION_GRAPH_TRACER bool "Kernel Function Graph Tracer" depends on HAVE_FUNCTION_GRAPH_TRACER depends on FUNCTION_TRACER depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE default y help Enable the kernel to trace a function at both its return and its entry. Its first purpose is to trace the duration of functions and draw a call graph for each thread with some information like the return value. This is done by setting the current return address on the current task structure into a stack of calls. config FUNCTION_GRAPH_RETVAL bool "Kernel Function Graph Return Value" depends on HAVE_FUNCTION_GRAPH_RETVAL depends on FUNCTION_GRAPH_TRACER default n help Support recording and printing the function return value when using function graph tracer. It can be helpful to locate functions that return errors. This feature is off by default, and you can enable it via the trace option funcgraph-retval. See Documentation/trace/ftrace.rst config FUNCTION_GRAPH_RETADDR bool "Kernel Function Graph Return Address" depends on FUNCTION_GRAPH_TRACER default n help Support recording and printing the function return address when using function graph tracer. It can be helpful to locate code line that the function is called. This feature is off by default, and you can enable it via the trace option funcgraph-retaddr. config DYNAMIC_FTRACE bool "enable/disable function tracing dynamically" depends on FUNCTION_TRACER depends on HAVE_DYNAMIC_FTRACE default y help This option will modify all the calls to function tracing dynamically (will patch them out of the binary image and replace them with a No-Op instruction) on boot up. During compile time, a table is made of all the locations that ftrace can function trace, and this table is linked into the kernel image. When this is enabled, functions can be individually enabled, and the functions not enabled will not affect performance of the system. See the files in /sys/kernel/tracing: available_filter_functions set_ftrace_filter set_ftrace_notrace This way a CONFIG_FUNCTION_TRACER kernel is slightly larger, but otherwise has native performance as long as no tracing is active. config DYNAMIC_FTRACE_WITH_REGS def_bool y depends on DYNAMIC_FTRACE depends on HAVE_DYNAMIC_FTRACE_WITH_REGS config DYNAMIC_FTRACE_WITH_DIRECT_CALLS def_bool y depends on DYNAMIC_FTRACE_WITH_REGS || DYNAMIC_FTRACE_WITH_ARGS depends on HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS config DYNAMIC_FTRACE_WITH_CALL_OPS def_bool y depends on HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS config DYNAMIC_FTRACE_WITH_ARGS def_bool y depends on DYNAMIC_FTRACE depends on HAVE_DYNAMIC_FTRACE_WITH_ARGS config FPROBE bool "Kernel Function Probe (fprobe)" depends on FUNCTION_TRACER depends on DYNAMIC_FTRACE_WITH_REGS depends on HAVE_RETHOOK select RETHOOK default n help This option enables kernel function probe (fprobe) based on ftrace. The fprobe is similar to kprobes, but probes only for kernel function entries and exits. This also can probe multiple functions by one fprobe. If unsure, say N. config FUNCTION_PROFILER bool "Kernel function profiler" depends on FUNCTION_TRACER default n help This option enables the kernel function profiler. A file is created in debugfs called function_profile_enabled which defaults to zero. When a 1 is echoed into this file profiling begins, and when a zero is entered, profiling stops. A "functions" file is created in the trace_stat directory; this file shows the list of functions that have been hit and their counters. If in doubt, say N. config STACK_TRACER bool "Trace max stack" depends on HAVE_FUNCTION_TRACER select FUNCTION_TRACER select STACKTRACE select KALLSYMS help This special tracer records the maximum stack footprint of the kernel and displays it in /sys/kernel/tracing/stack_trace. This tracer works by hooking into every function call that the kernel executes, and keeping a maximum stack depth value and stack-trace saved. If this is configured with DYNAMIC_FTRACE then it will not have any overhead while the stack tracer is disabled. To enable the stack tracer on bootup, pass in 'stacktrace' on the kernel command line. The stack tracer can also be enabled or disabled via the sysctl kernel.stack_tracer_enabled Say N if unsure. config TRACE_PREEMPT_TOGGLE bool help Enables hooks which will be called when preemption is first disabled, and last enabled. config IRQSOFF_TRACER bool "Interrupts-off Latency Tracer" default n depends on TRACE_IRQFLAGS_SUPPORT select TRACE_IRQFLAGS select GENERIC_TRACER select TRACER_MAX_TRACE select RING_BUFFER_ALLOW_SWAP select TRACER_SNAPSHOT select TRACER_SNAPSHOT_PER_CPU_SWAP help This option measures the time spent in irqs-off critical sections, with microsecond accuracy. The default measurement method is a maximum search, which is disabled by default and can be runtime (re-)started via: echo 0 > /sys/kernel/tracing/tracing_max_latency (Note that kernel size and overhead increase with this option enabled. This option and the preempt-off timing option can be used together or separately.) config PREEMPT_TRACER bool "Preemption-off Latency Tracer" default n depends on PREEMPTION select GENERIC_TRACER select TRACER_MAX_TRACE select RING_BUFFER_ALLOW_SWAP select TRACER_SNAPSHOT select TRACER_SNAPSHOT_PER_CPU_SWAP select TRACE_PREEMPT_TOGGLE help This option measures the time spent in preemption-off critical sections, with microsecond accuracy. The default measurement method is a maximum search, which is disabled by default and can be runtime (re-)started via: echo 0 > /sys/kernel/tracing/tracing_max_latency (Note that kernel size and overhead increase with this option enabled. This option and the irqs-off timing option can be used together or separately.) config SCHED_TRACER bool "Scheduling Latency Tracer" select GENERIC_TRACER select CONTEXT_SWITCH_TRACER select TRACER_MAX_TRACE select TRACER_SNAPSHOT help This tracer tracks the latency of the highest priority task to be scheduled in, starting from the point it has woken up. config HWLAT_TRACER bool "Tracer to detect hardware latencies (like SMIs)" select GENERIC_TRACER select TRACER_MAX_TRACE help This tracer, when enabled will create one or more kernel threads, depending on what the cpumask file is set to, which each thread spinning in a loop looking for interruptions caused by something other than the kernel. For example, if a System Management Interrupt (SMI) takes a noticeable amount of time, this tracer will detect it. This is useful for testing if a system is reliable for Real Time tasks. Some files are created in the tracing directory when this is enabled: hwlat_detector/width - time in usecs for how long to spin for hwlat_detector/window - time in usecs between the start of each iteration A kernel thread is created that will spin with interrupts disabled for "width" microseconds in every "window" cycle. It will not spin for "window - width" microseconds, where the system can continue to operate. The output will appear in the trace and trace_pipe files. When the tracer is not running, it has no affect on the system, but when it is running, it can cause the system to be periodically non responsive. Do not run this tracer on a production system. To enable this tracer, echo in "hwlat" into the current_tracer file. Every time a latency is greater than tracing_thresh, it will be recorded into the ring buffer. config OSNOISE_TRACER bool "OS Noise tracer" select GENERIC_TRACER select TRACER_MAX_TRACE help In the context of high-performance computing (HPC), the Operating System Noise (osnoise) refers to the interference experienced by an application due to activities inside the operating system. In the context of Linux, NMIs, IRQs, SoftIRQs, and any other system thread can cause noise to the system. Moreover, hardware-related jobs can also cause noise, for example, via SMIs. The osnoise tracer leverages the hwlat_detector by running a similar loop with preemption, SoftIRQs and IRQs enabled, thus allowing all the sources of osnoise during its execution. The osnoise tracer takes note of the entry and exit point of any source of interferences, increasing a per-cpu interference counter. It saves an interference counter for each source of interference. The interference counter for NMI, IRQs, SoftIRQs, and threads is increased anytime the tool observes these interferences' entry events. When a noise happens without any interference from the operating system level, the hardware noise counter increases, pointing to a hardware-related noise. In this way, osnoise can account for any source of interference. At the end of the period, the osnoise tracer prints the sum of all noise, the max single noise, the percentage of CPU available for the thread, and the counters for the noise sources. In addition to the tracer, a set of tracepoints were added to facilitate the identification of the osnoise source. The output will appear in the trace and trace_pipe files. To enable this tracer, echo in "osnoise" into the current_tracer file. config TIMERLAT_TRACER bool "Timerlat tracer" select OSNOISE_TRACER select GENERIC_TRACER help The timerlat tracer aims to help the preemptive kernel developers to find sources of wakeup latencies of real-time threads. The tracer creates a per-cpu kernel thread with real-time priority. The tracer thread sets a periodic timer to wakeup itself, and goes to sleep waiting for the timer to fire. At the wakeup, the thread then computes a wakeup latency value as the difference between the current time and the absolute time that the timer was set to expire. The tracer prints two lines at every activation. The first is the