[lttv.git] / lttng-xenomai / LinuxTraceToolkitViewer-0.8.61-xenoltt / doc / developer / format.html

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
  <title>The LTTng trace format</title>
</head>
  <body>

<h1>The LTTng trace format</h1>

<P>
This document describes the LTTng trace format. It should be used only by
developers who code the LTTng tracer or the traceread LTTV library, as this
library offers all the necessary abstractions on top of the raw trace data.

<P>
A trace is contained in a directory tree. To send a trace remotely,
the directory tree may be tar-gzipped. Trace foo, placed in the home
directory of user john, /home/john, would have the following content:

<PRE><TT>
$ cd /home/john
$ tree foo
foo/
|-- eventdefs
|   |-- core.xml
|   |-- fs.xml
|   |-- ipc.xml
|   |-- kernel.xml
|   |-- memory.xml
|   |-- network.xml
|   |-- process.xml
|   |-- s390_kernel.xml
|   |-- socket.xml
|   |-- timer.xml
|   `-- ...
|-- info
|   |-- bookmarks.xml
|   `-- system.xml
|-- control
|   |-- facilities_0
|   |-- facilities_1
|   |-- facilities_...
|   |-- interrupts_0
|   |-- interrupts_1
|   |-- interrupts_...
|   |-- modules_0
|   |-- modules_1
|   |-- modules_...
|   `-- processes_0
|   `-- processes_1
|   `-- processes_...
|-- cpu_0
|-- cpu_1
`-- cpu_...

</TT></PRE>

<P>
The eventdefs directory contains the events descriptions for all the
facilities used. The syntax is a simple subset of XML; XML is widely
known and easily parsed or hand edited. Each file contains one or more
<FACILITY NAME=name>...</FACILITY> elements. Indeed, several
facilities may have the same name but different content (and thus will
generate a different checksum). It typically happens when, while tracing
is enabled, a module using the named facility is unloaded, modified
(along with the description of some events), recompiled and reloaded.
Then, the trace will contain events from two different, similarly named,
facility versions.

<P>
A small number of events are predefined, part of the "core" facility, 
and are not present there. These "core" events include "facility_load", 
"facility_unload", "time_heartbeat" and "state_dump_facility_load".

<P>
The root directory contains a tracefile for each cpu, numbered from 0, 
in .trace format. A uniprocessor thus only contains the file cpu_0. 
A multi-processor with some unused (possibly hotplug) CPU slots may have some
unused CPU numbers. For instance a 8 way SMP board with 6 CPUs randomly 
installed may produce tracefiles named 0, 1, 2, 4, 6, 7.

<P>
The files in the control directory also follow the .trace format and are also
per cpu. 
The "facilities" file only contains "core" facility_load, facility_unload,
time_heartbeat and state_dump_facility_load events
and is used to determine the facilities used and the code range assigned 
to each facility. The other control files contain the initial system
state and various subsequent important events, for example process 
creations and exit. The interest of placing such subsequent events 
in control trace files instead of (or in addition to) in the per cpu 
trace files is that they may be accessed more quickly/conveniently 
and that they may be kept even when the per cpu files are overwritten 
in "flight recorder mode".

<P>
The info directory contains in system.xml a description of the system on which
the trace was created as well as different user annotations in bookmark.xml.
This directory may also contain various information about the trace, generated 
during trace analysis (statistics, index...).


<H2>Trace format</H2>

<P>
Each tracefile is divided into equal size blocks with a header at the beginning
of the block. Events are packed sequentially in the block starting right after
the block header.
<P>
Each block consists of :
<PRE><TT>
block start/end header
trace header
event 1 header
event 1 variable length data
event 2 header
event 2 variable length data
....
padding
</TT></PRE>

<P>
The block start/end header

<PRE><TT>
begin
	* the beginning of buffer information
	uint64 cycle_count
		* TSC at the beginning of the buffer
	uint64 freq
		* frequency of the CPUs at the beginning of the buffer.
end
	* the end of buffer information
	uint64 cycle_count
		* TSC at the beginning of the buffer
	uint64 freq
		* frequency of the CPUs at the end of the buffer.
uint32 lost_size
	* number of bytes of padding at the end of the buffer.
uint32 buf_size
	* size of the sub-buffer.
</TT></PRE>


<P>
The trace header

<PRE><TT>
uint32 magic_number
	* 0x00D6B7ED, used to check the trace byte order vs host byte order.
uint32 arch_type
	* Architecture type of the traced machine.
uint32 arch_variant
	* Architecture variant of the traced machine. May be unused on some arch.
uint32 float_word_order
	* Byte order of floats and doubles, sometimes different from integer byte
	  order. Useful only for user space traces.
uint8 arch_size
	* Size (in bytes) of the void * on the traced machine.
uint8 major_version
	* major version of the trace.
uint8 minor_version
	* minor version of the trace.
uint8 flight_recorder
	* Is flight recorder mode activated ? If yes, data might be missing
	  (overwritten) in the trace.
uint8	has_heartbeat
	* Does this trace have heartbeat timer event activated ?
		Yes (1) -> Event header has 32 bits TSC
		No (0) -> Event header has 64 bits TSC
uint8 has_alignment
	* Is the information in this trace aligned ?
		Yes (1) -> aligned on min(arch size, atomic data size).
		No (0) -> data is packed.
uint32 freq_scale
		event time is always calculated from :
			trace_start_time + ((event_tsc - trace_start_tsc) * (freq / freq_scale))
uint64 start_freq
	* CPUs clock frequency at the beginnig of the trace.
uint64 start_tsc
	* TSC at the beginning of the trace.
uint64 start_monotonic
	* monotonically increasing time at the beginning of the trace.
		(currently not supported)
start_time
	* Real time at the beginning of the trace (as given by date, adjusted by NTP)
		This is the only time reference with the real world : the rest of the trace
		has monotonically increasing time from this point (with TSC difference and
		clock frequency).
	uint32 seconds
	uint32 nanoseconds
</TT></PRE>


<P>
Event header

<P>
Event headers differs depending on those conditions : does the traced system has
a heartbeat timer ? Is tracing alignment activated ?

<P>
Event header :
<PRE><TT>
{ uint32 timestamp
	or
	uint64 timestamp }
	* if has_heartbeat : 32 LSB of the cycle counter at the event record time.
	* else : 64 bits complete cycle counter.
uint8 facility_id
	* Numerical ID of the facility corresponding to the event. See the facility
	  tracefile to know which facility ID matches which facility name and
		description.
uint8 event_id
	* Numerical ID of the event inside the facility.
uint16 event_size
	* Size of the variable length data that follows this header.
</TT></PRE>

<P>
Event header alignment

<P>
If trace alignment is activated (has_alignment), the event header is aligned
on the architecture size (void pointer size). In addition, a padding is
automatically added after the event header so the variable length data is
automatically aligned on the architecture size.

<P>

<H2>System description</H2>

<P>
The system type description, in system.xml, looks like:

<PRE><TT>
&lt;system 
 node_name="vaucluse"
 domainname="polymtl.ca" 
 cpu=4
 arch_size="ILP32" 
 endian="little" 
 kernel_name="Linux" 
 kernel_release="2.4.18-686-smp" 
 kernel_version="#1 SMP Sun Apr 14 12:07:19 EST 2002"
 machine="i686" 
 processor="unknown" 
 hardware_platform="unknown"
 operating_system="Linux" 
 ltt_major_version="2"
 ltt_minor_version="0"
 ltt_block_size="100000"
&gt;
Some comments about the system
&lt;/system&gt;
</TT></PRE>

<P>
The system attributes kernel_name, node_name, kernel_release,
 kernel_version, machine, processor, hardware_platform and operating_system
come from the uname(1) program. The domainname attribute is obtained from
the "hostname --domain" command. The arch_size attribute is one of
LP32, ILP32, LP64 or ILP64 and specifies the length in bits of integers (I),
long (L) and pointers (P). The endian attribute is "little" or "big".
While the arch_size and endian attributes could be deduced from the platform
type, having these explicit allows analysing traces from yet unknown
platforms. The cpu attribute specifies the maximum number of processors in
the system; only tracefiles 0 to this maximum - 1 may exist in the cpu
directory.

<P>
Within the system element, the text enclosed may describe further the
system traced.


<H2>Event type descriptions</H2>

<P>
A facility contains the descriptions of several event types. When a structure
is reused in several event types, a named type is defined and may be referenced
by several other event types or named types.

<PRE><TT>
&lt;facility name=facility_name&gt;
  &lt;description&gt;Some text&lt;/description&gt;
  &lt;event name=eventtype_name&gt;
    &lt;description&gt;Some text&lt;/description&gt;
    --type structure--
  &lt;/event&gt;
  ...
  &lt;type name=type_name&gt;
    --type structure--
  &lt;/type&gt;
&lt;/facility&gt;
</TT></PRE>

<P>
The type structure may be one of the following primitive type elements.
Whenever the keyword isize is used, the allowed values are 
short, medium, long, 1, 2, 4, 8, indicating the size in bytes.
The fsize keyword represents one of medium, long, 4 and 8 bytes.

<PRE><TT>
&lt;int size=isize format="printf format"/&gt;

&lt;uint size=isize format="printf format"/&gt;

&lt;float size=fsize format="printf format"/&gt;

&lt;string format="printf format"/&gt;

&lt;enum size=isize format="printf format"&gt;label1 label2 ...&lt;/enum&gt;
</TT></PRE>

<P>
The string is null terminated. For the enumeration, the size of the integer
used for its representation is specified.

<P>
The type structure may also be a compound type.

<PRE><TT>
&lt;array size=n&gt; --type structure-- &lt;/array&gt;

&lt;sequence lengthsize=isize&gt; --type structure-- &lt;/sequence&gt;

&lt;struct&gt;
  &lt;field name=field_name&gt;
    &lt;description&gt;Some text&lt;/description&gt;
    --type structure--
  &lt;/field&gt;
  ...
&lt;/struct&gt;

&lt;union typecodesize=isize&gt;
  &lt;field name=field_name&gt;
    &lt;description&gt;Some text&lt;/description&gt;
    --type structure--
  &lt;/field&gt;
  ...
&lt;/union&gt;
</TT></PRE>

<P>
Array is a fixed size array of length size. Sequence is a variable size
array with its length stored as a prepended uint of length lengthsize. 
A structure is simply an aggregation of fields. An union is one of its n 
fields (variant record), as indicated by a preceeding code (0 to n - 1)
of the specified size typecodesize.

<P>
Finally the type structure may be defined by referencing a named type.

<PRE><TT>
&lt;typeref name=type_name/&gt;
</PRE></TT>

<H2>Core events</H2>

<P>
The facility named "core" is always present and contains at least the
following event types.

<PRE><TT>
&lt;event name=facility_load&gt;
  &lt;description&gt;Facility used in the trace&lt;/description&gt;
  &lt;struct&gt;
    &lt;field name="name"&gt;&lt;string/&gt;&lt;/field&gt;
    &lt;field name="checksum"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="id"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="int_size"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="long_size"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="pointer_size"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="size_t_size"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="has_alignment"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
  &lt;/struct&gt;
&lt;/event&gt;

&lt;event name=state_dump_facility_load&gt;
  &lt;description&gt;Facility used in the trace&lt;/description&gt;
  &lt;struct&gt;
    &lt;field name="name"&gt;&lt;string/&gt;&lt;/field&gt;
    &lt;field name="checksum"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="id"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="int_size"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="long_size"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="pointer_size"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="size_t_size"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="has_alignment"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
  &lt;/struct&gt;
&lt;/event&gt;

&lt;event name=time_heartbeat&gt;
  &lt;description&gt;System time values sent periodically to minimize cycle counter 
    drift with respect to real time clock and to detect cycle counter
    rollovers
  &lt;/description&gt;
  &lt;typeref name=timestamp/&gt;
&lt;/event&gt;

&lt;type name=timestamp&gt;
  &lt;struct&gt;
    &lt;field name="seconds"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="nanoseconds"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="cycle_count"&gt;&lt;uint size=8/&gt;&lt;/field&gt;
  &lt;/struct&gt;
&lt;/event&gt;

</TT></PRE>

<H2>Control files</H2>

<P>
The interrupts file reflects the content of the /proc/interrupts system file.
It contains one event describing each interrupt. At trace start, events are
generated describing all the current interrupts. If the assignment of
interrupts changes later, due to devices or device drivers being activated or
deactivated, additional events may be added to the file. Each interrupt
event has the following structure.

<PRE><TT>
&lt;event name=interrupt&gt;
  &lt;description&gt;Interrupt request number assignment&lt;description&gt;
  &lt;struct&gt;
    &lt;field name="number"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="count"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="controller"&gt;&lt;string/&gt;&lt;/field&gt;
    &lt;field name="name"&gt;&lt;string/&gt;&lt;/field&gt;
  &lt;/struct&gt;
&lt;/event&gt;
</TT></PRE>

<P>
The processes file contains the list of processes already created when the
trace starts. Each process describing event is modeled after the 
/proc/self/status system file. The number of fields in this event is
expected to be expanded in the future to include groups, signal masks,
opened file descriptors and address maps.

<PRE><TT>
&lt;event name=process&gt;
  &lt;description&gt;Existing process&lt;description&gt;
  &lt;struct&gt;
    &lt;field name="name"&gt;&lt;string/&gt;&lt;/field&gt;
    &lt;field name="pid"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="ppid"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="tracer_pid"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="uid"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="euid"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="suid"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="fsuid"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="gid"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="egid"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="sgid"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="fsgid"&gt;&lt;uint size=4/&gt;&lt;/field&gt;
    &lt;field name="state"&gt;&lt;enum size=4&gt;
        Running WaitInterruptible WaitUninterruptible Zombie Traced Paging
    &lt;/enum&gt;&lt;/field&gt;
  &lt;/struct&gt;
&lt;/event&gt;
</TT></PRE>

<H2>Facilities</H2>

<P>
Facilities define a granularity of events grouping for filtering, activation
and compilation. Each facility does cost a table entry in the kernel (name,
checksum, event type code range), or somewhere between 20 and 30 bytes. Having
one facility per tracing statement in the kernel would be too much (assuming
that they eventually are routinely inserted in the kernel code and replace 
the 80000+ printk statements in some proportion). However, having a few 
facilities, up to a few tens, would make sense.

<P>
The "builtin" facility contains a small number of predefined events which must
always exist. The "core" facility contains a small subset of OS events which
are almost always of interest (scheduling, interrupts, faults, system calls).
Then, specialized facilities may exist for each subsystem (network, disks,
USB, SCSI...).
 

<H2>Bookmarks</H2>

<P>
Bookmarks are user supplied information added to a trace. They contain user
annotations attached to a time interval.

<PRE><TT>
&lt;bookmarks&gt;
  &lt;location name=name cpu=n start_time=t end_time=t&gt;Some text&lt;/location&gt;
  ...
&lt;/bookmarks&gt;
</TT></PRE>

<P>
The interval is defined using either "time=" or "start_time=" and 
"end_time=", or "cycle=" or "start_cycle=" and "end_cycle=". 
The time is in seconds with decimals up to nanoseconds and cycle counts 
are unsigned integers with a 64 bits range. The cpu attribute is optional.

</BODY>
</HTML>
Commit	Line	Data
0bc7c2cd	1	<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
	2	<html>
	3	<head>
	4	<title>The LTTng trace format</title>
	5	</head>
	6	<body>
	7
	8	<h1>The LTTng trace format</h1>
	9
	10	<P>
	11	This document describes the LTTng trace format. It should be used only by
	12	developers who code the LTTng tracer or the traceread LTTV library, as this
	13	library offers all the necessary abstractions on top of the raw trace data.
	14
	15	<P>
	16	A trace is contained in a directory tree. To send a trace remotely,
	17	the directory tree may be tar-gzipped. Trace foo, placed in the home
	18	directory of user john, /home/john, would have the following content:
	19
	20	<PRE><TT>
	21	$ cd /home/john
	22	$ tree foo
	23	foo/
	24	\|-- eventdefs
	25	\| \|-- core.xml
	26	\| \|-- fs.xml
	27	\| \|-- ipc.xml
	28	\| \|-- kernel.xml
	29	\| \|-- memory.xml
	30	\| \|-- network.xml
	31	\| \|-- process.xml
	32	\| \|-- s390_kernel.xml
	33	\| \|-- socket.xml
	34	\| \|-- timer.xml
	35	\| `-- ...
	36	\|-- info
	37	\| \|-- bookmarks.xml
	38	\| `-- system.xml
	39	\|-- control
	40	\| \|-- facilities_0
	41	\| \|-- facilities_1
	42	\| \|-- facilities_...
	43	\| \|-- interrupts_0
	44	\| \|-- interrupts_1
	45	\| \|-- interrupts_...
	46	\| \|-- modules_0
	47	\| \|-- modules_1
	48	\| \|-- modules_...
	49	\| `-- processes_0
	50	\| `-- processes_1
	51	\| `-- processes_...
	52	\|-- cpu_0
	53	\|-- cpu_1
	54	`-- cpu_...
	55
	56	</TT></PRE>
	57
	58	<P>
	59	The eventdefs directory contains the events descriptions for all the
	60	facilities used. The syntax is a simple subset of XML; XML is widely
	61	known and easily parsed or hand edited. Each file contains one or more
	62	<FACILITY NAME=name>...</FACILITY> elements. Indeed, several
	63	facilities may have the same name but different content (and thus will
	64	generate a different checksum). It typically happens when, while tracing
65	is enabled, a module using the named facility is unloaded, modified
66	(along with the description of some events), recompiled and reloaded.
67	Then, the trace will contain events from two different, similarly named,
68	facility versions.
69
70	<P>
71	A small number of events are predefined, part of the "core" facility,
72	and are not present there. These "core" events include "facility_load",
73	"facility_unload", "time_heartbeat" and "state_dump_facility_load".
74
75	<P>
76	The root directory contains a tracefile for each cpu, numbered from 0,
77	in .trace format. A uniprocessor thus only contains the file cpu_0.
78	A multi-processor with some unused (possibly hotplug) CPU slots may have some
79	unused CPU numbers. For instance a 8 way SMP board with 6 CPUs randomly
80	installed may produce tracefiles named 0, 1, 2, 4, 6, 7.
81
82	<P>
83	The files in the control directory also follow the .trace format and are also
84	per cpu.
85	The "facilities" file only contains "core" facility_load, facility_unload,
86	time_heartbeat and state_dump_facility_load events
87	and is used to determine the facilities used and the code range assigned
88	to each facility. The other control files contain the initial system
89	state and various subsequent important events, for example process
90	creations and exit. The interest of placing such subsequent events
91	in control trace files instead of (or in addition to) in the per cpu
92	trace files is that they may be accessed more quickly/conveniently
93	and that they may be kept even when the per cpu files are overwritten
94	in "flight recorder mode".
95
96	<P>
97	The info directory contains in system.xml a description of the system on which
98	the trace was created as well as different user annotations in bookmark.xml.
99	This directory may also contain various information about the trace, generated
100	during trace analysis (statistics, index...).
101
102
103	<H2>Trace format</H2>
104
105	<P>
106	Each tracefile is divided into equal size blocks with a header at the beginning
107	of the block. Events are packed sequentially in the block starting right after
108	the block header.
109	<P>
110	Each block consists of :
111	<PRE><TT>
112	block start/end header
113	trace header
114	event 1 header
115	event 1 variable length data
116	event 2 header
117	event 2 variable length data
118	....
119	padding
120	</TT></PRE>
121
122	<P>
123	The block start/end header
124
125	<PRE><TT>
126	begin
127	* the beginning of buffer information
128	uint64 cycle_count
129	* TSC at the beginning of the buffer
130	uint64 freq
131	* frequency of the CPUs at the beginning of the buffer.
132	end
133	* the end of buffer information
134	uint64 cycle_count
135	* TSC at the beginning of the buffer
136	uint64 freq
137	* frequency of the CPUs at the end of the buffer.
138	uint32 lost_size
139	* number of bytes of padding at the end of the buffer.
140	uint32 buf_size
141	* size of the sub-buffer.
142	</TT></PRE>
143
144
145
146	<P>
147	The trace header
148
149	<PRE><TT>
150	uint32 magic_number
151	* 0x00D6B7ED, used to check the trace byte order vs host byte order.
152	uint32 arch_type
153	* Architecture type of the traced machine.
154	uint32 arch_variant
155	* Architecture variant of the traced machine. May be unused on some arch.
156	uint32 float_word_order
157	* Byte order of floats and doubles, sometimes different from integer byte
158	order. Useful only for user space traces.
159	uint8 arch_size
160	* Size (in bytes) of the void * on the traced machine.
161	uint8 major_version
162	* major version of the trace.
163	uint8 minor_version
164	* minor version of the trace.
165	uint8 flight_recorder
166	* Is flight recorder mode activated ? If yes, data might be missing
167	(overwritten) in the trace.
168	uint8 has_heartbeat
169	* Does this trace have heartbeat timer event activated ?
170	Yes (1) -> Event header has 32 bits TSC
171	No (0) -> Event header has 64 bits TSC
172	uint8 has_alignment
173	* Is the information in this trace aligned ?
174	Yes (1) -> aligned on min(arch size, atomic data size).
175	No (0) -> data is packed.
176	uint32 freq_scale
177	event time is always calculated from :
178	trace_start_time + ((event_tsc - trace_start_tsc) * (freq / freq_scale))
179	uint64 start_freq
180	* CPUs clock frequency at the beginnig of the trace.
181	uint64 start_tsc
182	* TSC at the beginning of the trace.
183	uint64 start_monotonic
184	* monotonically increasing time at the beginning of the trace.
185	(currently not supported)
186	start_time
187	* Real time at the beginning of the trace (as given by date, adjusted by NTP)
188	This is the only time reference with the real world : the rest of the trace
189	has monotonically increasing time from this point (with TSC difference and
190	clock frequency).
191	uint32 seconds
192	uint32 nanoseconds
193	</TT></PRE>
194
195
196	<P>
197	Event header
198
199	<P>
200	Event headers differs depending on those conditions : does the traced system has
201	a heartbeat timer ? Is tracing alignment activated ?
202
203	<P>
204	Event header :
205	<PRE><TT>
206	{ uint32 timestamp
207	or
208	uint64 timestamp }
209	* if has_heartbeat : 32 LSB of the cycle counter at the event record time.
210	* else : 64 bits complete cycle counter.
211	uint8 facility_id
212	* Numerical ID of the facility corresponding to the event. See the facility
213	tracefile to know which facility ID matches which facility name and
214	description.
215	uint8 event_id
216	* Numerical ID of the event inside the facility.
217	uint16 event_size
218	* Size of the variable length data that follows this header.
219	</TT></PRE>
220
221	<P>
222	Event header alignment
223
224	<P>
225	If trace alignment is activated (has_alignment), the event header is aligned
226	on the architecture size (void pointer size). In addition, a padding is
227	automatically added after the event header so the variable length data is
228	automatically aligned on the architecture size.
229
230	<P>
231
232	<H2>System description</H2>
233
234	<P>
235	The system type description, in system.xml, looks like:
236
237	<PRE><TT>
238	<system
239	node_name="vaucluse"
240	domainname="polymtl.ca"
241	cpu=4
242	arch_size="ILP32"
243	endian="little"
244	kernel_name="Linux"
245	kernel_release="2.4.18-686-smp"
246	kernel_version="#1 SMP Sun Apr 14 12:07:19 EST 2002"
247	machine="i686"
248	processor="unknown"
249	hardware_platform="unknown"
250	operating_system="Linux"
251	ltt_major_version="2"
252	ltt_minor_version="0"
253	ltt_block_size="100000"
254	>
255	Some comments about the system
256	</system>
257	</TT></PRE>
258
259	<P>
260	The system attributes kernel_name, node_name, kernel_release,
261	kernel_version, machine, processor, hardware_platform and operating_system
262	come from the uname(1) program. The domainname attribute is obtained from
263	the "hostname --domain" command. The arch_size attribute is one of
264	LP32, ILP32, LP64 or ILP64 and specifies the length in bits of integers (I),
265	long (L) and pointers (P). The endian attribute is "little" or "big".
266	While the arch_size and endian attributes could be deduced from the platform
267	type, having these explicit allows analysing traces from yet unknown
268	platforms. The cpu attribute specifies the maximum number of processors in
269	the system; only tracefiles 0 to this maximum - 1 may exist in the cpu
270	directory.
271
272	<P>
273	Within the system element, the text enclosed may describe further the
274	system traced.
275
276
277	<H2>Event type descriptions</H2>
278
279	<P>
280	A facility contains the descriptions of several event types. When a structure
281	is reused in several event types, a named type is defined and may be referenced
282	by several other event types or named types.
283
284	<PRE><TT>
285	<facility name=facility_name>
286	<description>Some text</description>
287	<event name=eventtype_name>
288	<description>Some text</description>
289	--type structure--
290	</event>
291	...
292	<type name=type_name>
293	--type structure--
294	</type>
295	</facility>
296	</TT></PRE>
297
298	<P>
299	The type structure may be one of the following primitive type elements.
300	Whenever the keyword isize is used, the allowed values are
301	short, medium, long, 1, 2, 4, 8, indicating the size in bytes.
302	The fsize keyword represents one of medium, long, 4 and 8 bytes.
303
304	<PRE><TT>
305	<int size=isize format="printf format"/>
306
307	<uint size=isize format="printf format"/>
308
309	<float size=fsize format="printf format"/>
310
311	<string format="printf format"/>
312
313	<enum size=isize format="printf format">label1 label2 ...</enum>
314	</TT></PRE>
315
316	<P>
317	The string is null terminated. For the enumeration, the size of the integer
318	used for its representation is specified.
319
320	<P>
321	The type structure may also be a compound type.
322
323	<PRE><TT>
324	<array size=n> --type structure-- </array>
325
326	<sequence lengthsize=isize> --type structure-- </sequence>
327
328	<struct>
329	<field name=field_name>
330	<description>Some text</description>
331	--type structure--
332	</field>
333	...
334	</struct>
335
336	<union typecodesize=isize>
337	<field name=field_name>
338	<description>Some text</description>
339	--type structure--
340	</field>
341	...
342	</union>
343	</TT></PRE>
344
345	<P>
346	Array is a fixed size array of length size. Sequence is a variable size
347	array with its length stored as a prepended uint of length lengthsize.
348	A structure is simply an aggregation of fields. An union is one of its n
349	fields (variant record), as indicated by a preceeding code (0 to n - 1)
350	of the specified size typecodesize.
351
352	<P>
353	Finally the type structure may be defined by referencing a named type.
354
355	<PRE><TT>
356	<typeref name=type_name/>
357	</PRE></TT>
358
359	<H2>Core events</H2>
360
361	<P>
362	The facility named "core" is always present and contains at least the
363	following event types.
364
365	<PRE><TT>
366	<event name=facility_load>
367	<description>Facility used in the trace</description>
368	<struct>
369	<field name="name"><string/></field>
370	<field name="checksum"><uint size=4/></field>
371	<field name="id"><uint size=4/></field>
372	<field name="int_size"><uint size=4/></field>
373	<field name="long_size"><uint size=4/></field>
374	<field name="pointer_size"><uint size=4/></field>
375	<field name="size_t_size"><uint size=4/></field>
376	<field name="has_alignment"><uint size=4/></field>
377	</struct>
378	</event>
379
380	<event name=state_dump_facility_load>
381	<description>Facility used in the trace</description>
382	<struct>
383	<field name="name"><string/></field>
384	<field name="checksum"><uint size=4/></field>
385	<field name="id"><uint size=4/></field>
386	<field name="int_size"><uint size=4/></field>
387	<field name="long_size"><uint size=4/></field>
388	<field name="pointer_size"><uint size=4/></field>
389	<field name="size_t_size"><uint size=4/></field>
390	<field name="has_alignment"><uint size=4/></field>
391	</struct>
392	</event>
393
394	<event name=time_heartbeat>
395	<description>System time values sent periodically to minimize cycle counter
396	drift with respect to real time clock and to detect cycle counter
397	rollovers
398	</description>
399	<typeref name=timestamp/>
400	</event>
401
402	<type name=timestamp>
403	<struct>
404	<field name="seconds"><uint size=4/></field>
405	<field name="nanoseconds"><uint size=4/></field>
406	<field name="cycle_count"><uint size=8/></field>
407	</struct>
408	</event>
409
410	</TT></PRE>
411
412	<H2>Control files</H2>
413
414	<P>
415	The interrupts file reflects the content of the /proc/interrupts system file.
416	It contains one event describing each interrupt. At trace start, events are
417	generated describing all the current interrupts. If the assignment of
418	interrupts changes later, due to devices or device drivers being activated or
419	deactivated, additional events may be added to the file. Each interrupt
420	event has the following structure.
421
422	<PRE><TT>
423	<event name=interrupt>
424	<description>Interrupt request number assignment<description>
425	<struct>
426	<field name="number"><uint size=4/></field>
427	<field name="count"><uint size=4/></field>
428	<field name="controller"><string/></field>
429	<field name="name"><string/></field>
430	</struct>
431	</event>
432	</TT></PRE>
433
434	<P>
435	The processes file contains the list of processes already created when the
436	trace starts. Each process describing event is modeled after the
437	/proc/self/status system file. The number of fields in this event is
438	expected to be expanded in the future to include groups, signal masks,
439	opened file descriptors and address maps.
440
441	<PRE><TT>
442	<event name=process>
443	<description>Existing process<description>
444	<struct>
445	<field name="name"><string/></field>
446	<field name="pid"><uint size=4/></field>
447	<field name="ppid"><uint size=4/></field>
448	<field name="tracer_pid"><uint size=4/></field>
449	<field name="uid"><uint size=4/></field>
450	<field name="euid"><uint size=4/></field>
451	<field name="suid"><uint size=4/></field>
452	<field name="fsuid"><uint size=4/></field>
453	<field name="gid"><uint size=4/></field>
454	<field name="egid"><uint size=4/></field>
455	<field name="sgid"><uint size=4/></field>
456	<field name="fsgid"><uint size=4/></field>
457	<field name="state"><enum size=4>
458	Running WaitInterruptible WaitUninterruptible Zombie Traced Paging
459	</enum></field>
460	</struct>
461	</event>
462	</TT></PRE>
463
464	<H2>Facilities</H2>
465
466	<P>
467	Facilities define a granularity of events grouping for filtering, activation
468	and compilation. Each facility does cost a table entry in the kernel (name,
469	checksum, event type code range), or somewhere between 20 and 30 bytes. Having
470	one facility per tracing statement in the kernel would be too much (assuming
471	that they eventually are routinely inserted in the kernel code and replace
472	the 80000+ printk statements in some proportion). However, having a few
473	facilities, up to a few tens, would make sense.
474
475	<P>
476	The "builtin" facility contains a small number of predefined events which must
477	always exist. The "core" facility contains a small subset of OS events which
478	are almost always of interest (scheduling, interrupts, faults, system calls).
479	Then, specialized facilities may exist for each subsystem (network, disks,
480	USB, SCSI...).
481
482
483	<H2>Bookmarks</H2>
484
485	<P>
486	Bookmarks are user supplied information added to a trace. They contain user
487	annotations attached to a time interval.
488
489	<PRE><TT>
490	<bookmarks>
491	<location name=name cpu=n start_time=t end_time=t>Some text</location>
492	...
493	</bookmarks>
494	</TT></PRE>
495
496	<P>
497	The interval is defined using either "time=" or "start_time=" and
498	"end_time=", or "cycle=" or "start_cycle=" and "end_cycle=".
499	The time is in seconds with decimals up to nanoseconds and cycle counts
500	are unsigned integers with a 64 bits range. The cpu attribute is optional.
501
502	</BODY>
503	</HTML>
504
505
506
507