TNF_KERNEL_PROBES(4) File Formats and Configurations TNF_KERNEL_PROBES(4)


NAME


tnf_kernel_probes - TNF kernel probes

DESCRIPTION


The set of probes (trace instrumentation points) available in the
standard kernel. The probes log trace data to a kernel trace buffer in
Trace Normal Form (TNF). Kernel probes are controlled by prex(1). A
snapshot of the kernel trace buffer can be made using tnfxtract(1) and
examined using tnfdump(1).


Each probe has a name and is associated with a set of symbolic keys, or
categories. These are used to select and control probes from prex(1). A
probe that is enabled for tracing generates a TNF record, called an
event record. An event record contains two common members and may contain
other probe-specific data members.

Common Members


tnf_probe_event tag
tnf_time_delta time_delta


tag
Encodes TNF references to two other records:

tag
Describes the layout of the event record.


schedule
Identifies the writing thread and also contains
a 64-bit base time in nanoseconds.


time_delta
A 32-bit time offset from the base time; the sum of the two
times is the actual time of the event.


Threads


thread_create
tnf_kthread_id tid
tnf_pid pid
tnf_symbol start_pc


Thread creation event.

tid
The thread identifier for the new thread.


pid
The process identifier for the new thread.


start_pc
The kernel address of its start routine.


thread_state
tnf_kthread_id tid
tnf_microstate state


Thread microstate transition events.

tid
Optional; if it is absent, the event is for the writing thread,
otherwise the event is for the specified thread.


state
Indicates the thread state:

o Running in user mode.

o Running in system mode.

o Asleep waiting for a user-mode lock.

o Asleep on a kernel object.

o Runnable (waiting for a cpu).

o Stopped.
The values of this member are defined in <sys/msacct.h>. Note
that to reduce trace output, transitions between the system and
user microstates that are induced by system calls are not
traced. This information is implicit in the system call entry
and exit events.


thread_exit
Thread termination event for writing thread. This probe has no data
members other than the common members.

Scheduling



thread_queue
tnf_kthread_id tid
tnf_cpuid cpuid
tnf_long priority
tnf_ulong queue_length


Thread scheduling events. These are triggered when a runnable thread is
placed on a dispatch queue.

cpuid
Specifies the cpu to which the queue is attached.


priority
The (global) dispatch priority of the thread.


queue_length
The current length of the cpu's dispatch queue.


Blocking


thread_block
tnf_opaque reason
tnf_symbols stack


Thread blockage event. This probe captures a partial stack backtrace
when the current thread blocks.

reason
The address of the object on which the thread is blocking.


symbols
References a TNF array of kernel addresses representing the
PCs on the stack at the time the thread blocks.


System Calls


syscall_start
tnf_sysnum sysnum


System call entry event.

sysnum
The system call number. The writing thread implicitly enters
the system microstate with this event.


syscall_end
tnf_long rval1
tnf_long rval2
tnf_long errno


System call exit event.

rval1 and rval2
The two return values of the system call


errno
The error return.


The writing thread implicitly enters the user microstate with this event.

Page Faults


address_fault
tnf_opaque address
tnf_fault_type fault_type
tnf_seg_access access


Address-space fault event.

address
Gives the faulting virtual address.


fault_type
Gives the fault type: invalid page, protection fault,
software requested locking or unlocking.


access
Gives the desired access protection: read, write, execute
or create. The values for these two members are defined in
<vm/seg_enum.h>.


major_fault
tnf_opaque vnode
tnf_offset offset


Major page fault event. The faulting page is mapped to the file given by
the vnode member, at the given offset into the file. (The faulting
virtual address is in the most recent address_fault event for the writing
thread.)

anon_private
tnf_opaque address


Copy-on-write page fault event.

address
The virtual address at which the new page is mapped.


anon_zero
tnf_opaque address


Zero-fill page fault event.

address
The virtual address at which the new page is mapped.


page_unmap
tnf_opaque vnode
tnf_offset offset


Page unmapping event. This probe marks the unmapping of a file system
page from the system.

vnode and offset
Identifies the file and offset of the page being
unmapped.


Pageins and Pageouts


pagein
tnf_opaque vnode
tnf_offset offset
tnf_size size


Pagein start event. This event signals the initiation of pagein I/O.

vnodeandoffset
Identifies the file and offset to be paged in.


size
Specifies the number of bytes to be paged in.


pageout
tnf_opaque vnode
tnf_ulong pages_pageout
tnf_ulong pages_freed
tnf_ulong pages_reclaimed


Pageout completion event. This event signals the completion of pageout
I/O.

vnode
Identifies the file of the pageout request.


pages_pageout
The number of pages written out.


pages_freed
The number of pages freed after being written out.


pages_reclaimed
The number of pages reclaimed after being written out.


Page Daemon (Page Stealer)
pageout_scan_start
tnf_ulong pages_free
tnf_ulong pages_needed


Page daemon scan start event. This event signals the beginning of one
iteration of the page daemon.

pages_free
The number of free pages in the system.


pages_needed
The number of pages desired free.


pageout_scan_end
tnf_ulong pages_free
tnf_ulong pages_scanned


Page daemon scan end event. This event signals the end of one iteration
of the page daemon.

pages_free
The number of free pages in the system.


pages_scanned
The number of pages examined by the page daemon.
(Potentially more pages will be freed when any queued
pageout requests complete.)


Swapper


swapout_process
tnf_pid pid
tnf_ulong page_count


Address space swapout event. This event marks the swapping out of a
process address space.

pid
Identifies the process.


page_count
Reports the number of pages either freed or queued for
pageout.


swapout_lwp
tnf_pid pid
tnf_lwpid lwpid
tnf_kthread_id tid
tnf_ulong page_count


Light-weight process swapout event. This event marks the swapping out of
an LWP and its stack.

pid
The LWP's process identifier


lwpid
The LWP identifier


tid member
The LWP's kernel thread identifier.


page_count
The number of pages swapped out.


swapin_lwp
tnf_pid pid
tnf_lwpid lwpid
tnf_kthread_id tid
tnf_ulong page_count


Light-weight process swapin event. This event marks the swapping in of
an LWP and its stack.

pid
The LWP's process identifier.


lwpid
The LWP identifier.


tid
The LWP's kernel thread identifier.


page_count
The number of pages swapped in.


Local I/O
strategy
tnf_device device
tnf_diskaddr block
tnf_size size
tnf_opaque buf
tnf_bioflags flags


Block I/O strategy event. This event marks a call to the strategy(9E)
function of a block device driver.

device
Contains the major and minor numbers of the device.


block
The logical block number to be accessed on the device.


size
The size of the I/O request.


buf
The kernel address of the buf(9S) structure associated with the
transfer.


flags
The buf(9S) flags associated with the transfer.


biodone
tnf_device device
tnf_diskaddr block
tnf_opaque buf


Buffered I/O completion event. This event marks calls to the biodone(9F)
function.

device
Contains the major and minor numbers of the device.


block
The logical block number accessed on the device.


buf
The kernel address of the buf(9S) structure associated with the
transfer.


physio_start
tnf_device device
tnf_offset offset
tnf_size size
tnf_bioflags rw


Raw I/O start event. This event marks entry into the physio(9F) function
which performs unbuffered I/O.

device
Contains the major and minor numbers of the device of the
transfer.


offset
The logical offset on the device for the transfer.


size
The number of bytes to be transferred.


rw
The direction of the transfer: read or write (see buf(9S)).


physio_end
tnf_device device


Raw I/O end event. This event marks exit from the physio(9F) function.

device
The major and minor numbers of the device of the transfer.


USAGE


Use the prex utility to control kernel probes. The standard prex commands
to list and manipulate probes are available to you, along with commands
to set up and manage kernel tracing.


Kernel probes write trace records into a kernel trace buffer. You must
copy the buffer into a TNF file for post-processing; use the tnfxtract
utility for this.


You use the tnfdump utility to examine a kernel trace file. This is
exactly the same as examining a user-level trace file.


The steps you typically follow to take a kernel trace are:

1. Become superuser (su).

2. Allocate a kernel trace buffer of the desired size (prex).

3. Select the probes you want to trace and enable (prex).

4. Turn kernel tracing on (prex).

5. Run your application.

6. Turn kernel tracing off (prex).

7. Extract the kernel trace buffer (tnfxtract).

8. Disable all probes (prex).

9. Deallocate the kernel trace buffer (prex).

10. Examine the trace file (tnfdump).


A convenient way to follow these steps is to use two shell windows; run
an interactive prex session in one, and run your application and
tnfxtract in the other.

SEE ALSO


prex(1), tnfdump(1), tnfxtract(1), libtnfctl(3TNF), TNF_PROBE(3TNF),
tracing(3TNF), strategy(9E), biodone(9F), physio(9F), buf(9S)


May 16, 2020 TNF_KERNEL_PROBES(4)