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+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/2002/REC-xhtml1-20020801/DTD/xhtml1-strict.dtd">
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+
<head>
<title>The LTTng trace format</title>
</head>
- <body>
+
+<body>
<h1>The LTTng trace format</h1>
-<P>
-This document describes the LTTng trace format. It should be used only by
+<p>
+<em>Last update: 2008/06/02</em>
+</p>
+
+<p>
+This document describes the LTTng trace format. It should be useful mainly to
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>
-<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:
+<p>
+A trace is contained in a directory tree. To send a trace remotely, the
+directory tree may be tar-gzipped. The trace <tt>foo</tt>, placed in the home
+directory of user john, /home/john, would have the following contents:
+</p>
-<PRE><TT>
+<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
| |-- modules_0
| |-- modules_1
| |-- modules_...
-| `-- processes_0
-| `-- processes_1
+| |-- network_0
+| |-- network_1
+| |-- network_...
+| |-- 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>
+</tt></pre>
+
+<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
+unused CPU numbers. For instance an 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>
+</p>
+
+<p>
+The files in the control directory also follow the .trace format and are
+also per cpu. The "facilities" files only contain "core" marker_id,
+marker_format and time_heartbeat events. The first two are used to describe the
+events that are in the trace. 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>
+
+<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>
+</p>
+
+<p>
Each block consists of :
-<PRE><TT>
+</p>
+
+<pre><tt>
block start/end header
trace header
event 1 header
event 2 variable length data
....
padding
-</TT></PRE>
+</tt></pre>
-<P>
-The block start/end header
+<h3>The block start/end header</h3>
-<PRE><TT>
+<pre><tt>
begin
* the beginning of buffer information
- timestamp
- * Used only when no TSC is available.
- uint32 seconds
- uint32 microseconds
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
- timestamp
- * Used only when no TSC is available.
- uint32 seconds
- uint32 microseconds
uint64 cycle_count
- * TSC at the beginning of the buffer
+ * TSC at the end of the buffer
uint64 freq
- * frequency of the CPUs at the beginning of the buffer.
+ * 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>
+</tt></pre>
-<P>
-The trace header
+<h3>The trace header</h3>
-<PRE><TT>
+<pre><tt>
uint32 magic_number
* 0x00D6B7ED, used to check the trace byte order vs host byte order.
uint32 arch_type
* 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).
+uint8 alignment
+ * Are event headers in this trace aligned ?
+ Yes -> the value indicates the alignment
No (0) -> data is packed.
-uint8 has_tsc
- * Does the traced machine has a working TSC ?
- Yes (1) -> event time is calculated from :
- trace_start_time + ((event_tsc - trace_start_tsc) * freq)
- No (0) -> event time is calculated from :
- trace_start_time
- + (buffer start timestamp - trace start_monotonic)
- + (event_time_delta)
- (not supported)
+uint8 tsc_lsb_truncate
+ * Used for compact channels
+uint8 tscbits
+ * Used for compact channels
+uint8 compact_data_shift
+ * Used for compact channels
+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
clock frequency).
uint32 seconds
uint32 nanoseconds
-</TT></PRE>
+</tt></pre>
-<P>
-Event header
+<h3>Event header</h3>
-<P>
-Event headers differs depending on those conditions : does the traced system has
-a heartbeat timer ? Is tracing alignment activated ?
+<p>
+Event headers differ according to the following conditions : does the
+traced system have a heartbeat timer? Is tracing alignment activated?
+</p>
-<P>
+<p>
Event header :
-<PRE><TT>
+</p>
+<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.
- * note : if there is no working TSC (has_tsc == 0), then this field contains
- either the complete monotonically increasing time or the time delta from the
- previous heartbeat event. (unsupported)
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
* Numerical ID of the event inside the facility.
uint16 event_size
* Size of the variable length data that follows this header.
-</TT></PRE>
+</tt></pre>
-<P>
+<p>
Event header alignment
+</p>
-<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>
+<p>
+If trace alignment is activated (<tt>alignment</tt>), the event header is
+aligned. In addition, 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>
+<!--
+<h2>System description</h2>
-<P>
+<p>
The system type description, in system.xml, looks like:
+</p>
-<PRE><TT>
+<pre><tt>
<system
node_name="vaucluse"
domainname="polymtl.ca"
>
Some comments about the system
</system>
-</TT></PRE>
+</tt></pre>
-<P>
+<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
+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
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>
-<P>
+<p>
Within the system element, the text enclosed may describe further the
system traced.
+</p>
-<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>
-<facility name=facility_name>
- <description>Some text</description>
- <event name=eventtype_name>
- <description>Some text</description>
- --type structure--
- </event>
- ...
- <type name=type_name>
- --type structure--
- </type>
-</facility>
-</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>
-<int size=isize format="printf format"/>
-
-<uint size=isize format="printf format"/>
+<h2>Bookmarks</h2>
-<float size=fsize format="printf format"/>
-
-<string format="printf format"/>
-
-<enum size=isize format="printf format">label1 label2 ...</enum>
-</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>
-<array size=n> --type structure-- </array>
-
-<sequence lengthsize=isize> --type structure-- </sequence>
-
-<struct>
- <field name=field_name>
- <description>Some text</description>
- --type structure--
- </field>
- ...
-</struct>
-
-<union typecodesize=isize>
- <field name=field_name>
- <description>Some text</description>
- --type structure--
- </field>
- ...
-</union>
-</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>
-<typeref name=type_name/>
-</PRE></TT>
-
-<H2>Builtin events</H2>
-
-<P>
-The facility named "builtin" is always present and contains at least the
-following event types.
-
-<PRE><TT>
-<event name=facility_load>
- <description>Facility used in the trace</description>
- <struct>
- <field name="name"><string/></field>
- <field name="checksum"><uint size=4/></field>
- <field name="base_code"><uint size=4/></field>
- </struct>
-</event>
-
-<event name=block_start>
- <description>Block start timestamp</description>
- <typeref name=block_timestamp/>
-</event>
-
-<event name=block_end>
- <description>Block end timestamp</description>
- <typeref name=block_timestamp/>
-</event>
-
-<event name=time_heartbeat>
- <description>System time values sent periodically to minimize cycle counter
- drift with respect to real time clock and to detect cycle counter
- rollovers
- </description>
- <typeref name=timestamp/>
-</event>
-
-<type name=block_timestamp>
- <struct>
- <field name=timestamp><typeref name=timestamp></field>
- <field name=block_id><uint size=4/></field>
- </struct>
-</type>
-
-<type name=timestamp>
- <struct>
- <field name=time><typeref name=timespec/></event>
- <field name="cycle_count"><uint size=8/></field>
- </struct>
-</event>
-
-<type name=timespec>
- <struct>
- <field name="seconds"><uint size=4/></field>
- <field name="nanoseconds"><uint size=4/></field>
- </struct>
-</type>
-</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>
-<event name=interrupt>
- <description>Interrupt request number assignment<description>
- <struct>
- <field name="number"><uint size=4/></field>
- <field name="count"><uint size=4/></field>
- <field name="controller"><string/></field>
- <field name="name"><string/></field>
- </struct>
-</event>
-</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>
-<event name=process>
- <description>Existing process<description>
- <struct>
- <field name="name"><string/></field>
- <field name="pid"><uint size=4/></field>
- <field name="ppid"><uint size=4/></field>
- <field name="tracer_pid"><uint size=4/></field>
- <field name="uid"><uint size=4/></field>
- <field name="euid"><uint size=4/></field>
- <field name="suid"><uint size=4/></field>
- <field name="fsuid"><uint size=4/></field>
- <field name="gid"><uint size=4/></field>
- <field name="egid"><uint size=4/></field>
- <field name="sgid"><uint size=4/></field>
- <field name="fsgid"><uint size=4/></field>
- <field name="state"><enum size=4>
- Running WaitInterruptible WaitUninterruptible Zombie Traced Paging
- </enum></field>
- </struct>
-</event>
-</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>
+<p>
Bookmarks are user supplied information added to a trace. They contain user
annotations attached to a time interval.
+</p>
-<PRE><TT>
+
+<pre><tt>
<bookmarks>
<location name=name cpu=n start_time=t end_time=t>Some text</location>
...
</bookmarks>
-</TT></PRE>
+</tt></pre>
-<P>
+<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.
+</p>
-</BODY>
-</HTML>
-
-
-
-
+-->
+</body>
+</html>
projects / lttv.git / blobdiff