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File Formats | tnf_kernel_probes(4) |
| tnf_kernel_probes - TNF kernel probes |
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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
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tnf_probe_event tag
tnf_time_delta time_delta
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tag
- Encodes TNF references to two other records:
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tag
- Describes the layout of the event
record.
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schedule
- Identifies the writing thread and also contains a 64-bit base time
in nanoseconds.
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time_delta
- A 32-bit time offset from the base time; the sum of the
two times is the actual time of the event.
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Threads
| thread_create
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tnf_kthread_id tid
tnf_pid pid
tnf_symbol start_pc
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Thread creation event.
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tid
- The thread identifier for the new
thread.
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pid
- The process identifier for the new thread.
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start_pc
- The kernel address of its start routine.
thread_state
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tnf_kthread_id tid
tnf_microstate state
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Thread microstate transition events.
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tid
- Optional; if it is absent, the event
is for the writing thread, otherwise the event is for the specified thread.
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state
- Indicates the thread state:
- Running in user mode.
- Running in system mode.
- Asleep waiting for a user-mode lock.
- Asleep on a kernel object.
- Runnable (waiting for a cpu).
- 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_exitThread termination event for writing thread. This probe has no data
members other than the common members.
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Scheduling
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thread_queue
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tnf_kthread_id tid
tnf_cpuid cpuid
tnf_long priority
tnf_ulong queue_length
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Thread scheduling events. These are triggered when a runnable thread
is placed on a dispatch queue.
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cpuid
- Specifies the cpu to which the
queue is attached.
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priority
- The (global) dispatch priority of the thread.
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queue_length
- The current length of the cpu's dispatch queue.
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Blocking
| thread_block
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tnf_opaque reason
tnf_symbols stack
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Thread blockage event. This probe captures a partial stack backtrace
when the current thread blocks.
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reason
- The address of the object on
which the thread is blocking.
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symbols
- References a TNF array of kernel
addresses representing the PCs on the stack at the time the thread blocks.
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System Calls
| syscall_start
System call entry event.
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sysnum
- The system call number. The
writing thread implicitly enters the system microstate
with this event.
syscall_end
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tnf_long rval1
tnf_long rval2
tnf_long errno
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System call exit event.
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rval1 and rval2
- The two return values of the system call
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errno
- The error return.
The writing thread implicitly enters the user
microstate with this event.
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Page Faults
| address_fault
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tnf_opaque address
tnf_fault_type fault_type
tnf_seg_access access
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Address-space fault event.
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address
- Gives the faulting virtual address.
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fault_type
- Gives the fault type: invalid page, protection fault, software requested
locking or unlocking.
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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
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tnf_opaque vnode
tnf_offset offset
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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
Copy-on-write page fault event.
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address
- The virtual address at which
the new page is mapped.
anon_zero
Zero-fill page fault event.
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address
- The virtual address at which
the new page is mapped.
page_unmap
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tnf_opaque vnode
tnf_offset offset
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Page unmapping event. This probe marks the unmapping of a file system
page from the system.
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vnode and offset
- Identifies the file and offset of the page being unmapped.
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Pageins and Pageouts
| pagein
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tnf_opaque vnode
tnf_offset offset
tnf_size size
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Pagein start event. This event signals the initiation of pagein I/O.
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vnodeandoffset
- Identifyies the file and offset to be paged in.
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size
- Specifies the number of bytes to be paged in.
pageout
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tnf_opaque vnode
tnf_ulong pages_pageout
tnf_ulong pages_freed
tnf_ulong pages_reclaimed
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Pageout completion event. This event signals the completion of pageout
I/O.
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vnode
- Identifies the file of the pageout
request.
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pages_pageout
- The number of pages written out.
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pages_freed
- The number of pages freed after being written out.
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pages_reclaimed
- The number of pages reclaimed after being written out.
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Page Daemon (Page Stealer)
| pageout_scan_start
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tnf_ulong pages_free
tnf_ulong pages_needed
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Page daemon scan start event. This event signals the beginning of
one iteration of the page daemon.
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pages_free
- The number of free pages
in the system.
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pages_needed
- The number of pages desired free.
pageout_scan_end
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tnf_ulong pages_free
tnf_ulong pages_scanned
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Page daemon scan end event. This event signals the end of one iteration
of the page daemon.
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pages_free
- The number of free pages
in the system.
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pages_scanned
- The number of pages examined by the page daemon. (Potentially more
pages will be freed when any queued pageout requests complete.)
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Swapper
| swapout_process
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tnf_pid pid
tnf_ulong page_count
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Address space swapout event. This event marks the swapping out of
a process address space.
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pid
- Identifies the process.
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page_count
- Reports the number of pages either freed or queued for pageout.
swapout_lwp
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tnf_pid pid
tnf_lwpid lwpid
tnf_kthread_id tid
tnf_ulong page_count
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Light-weight process swapout event. This event marks the swapping
out of an LWP and its stack.
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pid
- The LWP's process identifier
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lwpid
- The LWP identifier
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tid member
- The LWP's kernel thread
identifier.
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page_count
- The number of pages swapped out.
swapin_lwp
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tnf_pid pid
tnf_lwpid lwpid
tnf_kthread_id tid
tnf_ulong page_count
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Light-weight process swapin event. This event marks the swapping
in of an LWP and its stack.
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pid
- The LWP's process identifier.
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lwpid
- The LWP identifier.
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tid
- The LWP's kernel thread identifier.
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page_count
- The number of pages swapped in.
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Local I/O
| strategy
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tnf_device device
tnf_diskaddr block
tnf_size size
tnf_opaque buf
tnf_bioflags flags
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Block I/O strategy event. This event marks a call to the strategy(9E) function of a block device
driver.
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device
- Contains the major and minor
numbers of the device.
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block
- The logical block number to be accessed on the device.
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size
- The size of the I/O request.
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buf
- The kernel address of the buf(9S)
structure associated with the transfer.
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flags
- The buf(9S) flags
associated with the transfer.
biodone
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tnf_device device
tnf_diskaddr block
tnf_opaque buf
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Buffered I/O completion event. This event marks calls to the biodone(9F)
function.
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device
- Contains the major and minor
numbers of the device.
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block
- The logical block number accessed on the device.
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buf
- The kernel address of the buf(9S)
structure associated with the transfer.
physio_start
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tnf_device device
tnf_offset offset
tnf_size size
tnf_bioflags rw
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Raw I/O start event. This event marks entry into the physio(9F) fufnction which performs
unbuffered I/O.
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device
- Contains the major and minor
numbers of the device of the transfer.
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offset
- The logical offset on the device for the transfer.
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size
- The number of bytes to be transferred.
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rw
- The direction of the transfer: read or write (see buf(9S)).
physio_end
Raw I/O end event. This event marks exit from the physio(9F) fufnction.
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device
- The major and minor numbers of
the device of the transfer.
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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:
- Become superuser (su).
- Allocate a kernel trace buffer of the desired
size (prex).
- Select the probes you want to trace and enable
(prex).
- Turn kernel tracing on (prex).
- Run your application.
- Turn kernel tracing off (prex).
- Extract the kernel trace buffer (tnfxtract).
- Disable all probes (prex).
- Deallocate the kernel trace buffer (prex).
- 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.
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