Xserver-DTrace.xml [plain text]
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<!ENTITY % defs SYSTEM "/xserver/doc/xml/xserver.ent"> %defs;
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<article id="Xserver-DTrace">
<articleinfo>
<title>Xserver provider for DTrace</title>
<author>
<firstname>Alan</firstname><surname>Coopersmith</surname>
<affiliation>
<orgname>Oracle Corporation</orgname>
<orgdiv>Solaris Engineering</orgdiv>
</affiliation>
</author>
<releaseinfo>X.Org Xserver version &xserver.version;</releaseinfo>
<legalnotice id="copyright">
<para>
Copyright (c) 2005, 2006, 2007, 2010, Oracle and/or its affiliates.
All rights reserved.
</para><para>
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following conditions:
</para><para>
The above copyright notice and this permission notice (including the next
paragraph) shall be included in all copies or substantial portions of the
Software.
</para><para>
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.
</para>
</legalnotice>
</articleinfo>
<sect1 id="introduction">
<title>Introduction</title>
<para>
This page provides details on a
<ulink url="http://wikis.sun.com/display/DTrace/Statically+Defined+Tracing+for+User+Applications">statically defined user application tracing provider</ulink>
for the
<ulink url="http://hub.opensolaris.org/bin/view/Community+Group+dtrace/">DTrace</ulink>
facility in <productname>Solaris</productname> 10,
<productname>MacOS X</productname> 10.5, and later releases. This
provider instruments various points in the X server, to allow
tracing what client applications are up to.
</para>
<para>
The provider was integrated into the X.Org git master repository
with Solaris 10 & OpenSolaris support for the Xserver 1.4 release,
released in 2007 with X11R7.3. Support for DTrace on MacOS X
was added in Xserver 1.7.
</para>
<para>
These probes expose the request and reply structure of the X protocol
between clients and the X server, so an understanding of that basic
nature will aid in learning how to use these probes.
</para>
</sect1>
<sect1 id="probes">
<title>Available probes</title>
<para>
Due to the way User-Defined DTrace probes work, arguments to
these probes all bear undistinguished names of
<parameter>arg0</parameter>, <parameter>arg1</parameter>,
<parameter>arg2</parameter>, etc. These tables should help you
determine what the real data is for each of the probe arguments.
<table id="Probes_and_their_arguments">
<title>Probes and their arguments</title>
<tgroup cols='7'>
<colspec colname="probe" colwidth="2*"/>
<colspec colname="desc" colwidth="3*"/>
<colspec colname="arg0" colwidth="1*"/>
<colspec colname="arg1" colwidth="1*"/>
<colspec colname="arg2" colwidth="1*"/>
<colspec colname="arg3" colwidth="1*"/>
<colspec colname="arg4" colwidth="1*"/>
<spanspec spanname="all" namest="probe" nameend="arg4"/>
<thead>
<row>
<entry>Probe name</entry>
<entry>Description</entry>
<entry>arg0</entry>
<entry>arg1</entry>
<entry>arg2</entry>
<entry>arg3</entry>
<entry>arg4</entry>
</row>
</thead>
<tbody>
<row>
<entry spanname="all" class="grouphead">Request Probes</entry>
</row>
<row>
<entry>request-start</entry>
<entry>Called just before processing each client request.</entry>
<entry><parameter>requestName</parameter></entry>
<entry><parameter>requestCode</parameter></entry>
<entry><parameter>requestLength</parameter></entry>
<entry><parameter>clientId</parameter></entry>
<entry><parameter>requestBuffer</parameter></entry>
</row>
<row>
<entry>request-done</entry>
<entry>Called just after processing each client request.</entry>
<entry><parameter>requestName</parameter></entry>
<entry><parameter>requestCode</parameter></entry>
<entry><parameter>sequenceNumber</parameter></entry>
<entry><parameter>clientId</parameter></entry>
<entry><parameter>resultCode</parameter></entry>
</row>
<row>
<entry spanname="all" class="grouphead">Event Probes</entry>
</row>
<row>
<entry>send-event</entry>
<entry>Called just before send each event to a client.</entry>
<entry><parameter>clientId</parameter></entry>
<entry><parameter>eventCode</parameter></entry>
<entry><parameter>eventBuffer</parameter></entry>
<entry nameend="arg4" class="unused"/>
</row>
<row>
<entry spanname="all" class="grouphead">Client Connection Probes</entry>
</row>
<row>
<entry>client-connect</entry>
<entry>Called when a new connection is opened from a client</entry>
<entry><parameter>clientId</parameter></entry>
<entry><parameter>clientFD</parameter></entry>
<entry nameend="arg4" class="unused"/>
</row>
<row>
<entry>client-auth</entry>
<entry>Called when client authenticates (normally just after connection opened)</entry>
<entry><parameter>clientId</parameter></entry>
<entry><parameter>clientAddr</parameter></entry>
<entry><parameter>clientPid</parameter></entry>
<entry><parameter>clientZoneId</parameter></entry>
<entry nameend="arg4" class="unused"/>
</row>
<row>
<entry>client-disconnect</entry>
<entry>Called when a client connection is closed</entry>
<entry><parameter>clientId</parameter></entry>
<entry nameend="arg4" class="unused"/>
</row>
<row>
<entry spanname="all" class="grouphead">Resource Allocation Probes</entry>
</row>
<row>
<entry>resource-alloc</entry>
<entry>Called when a new resource (pixmap, gc, colormap, etc.) is allocated</entry>
<entry><parameter>resourceId</parameter></entry>
<entry><parameter>resourceTypeId</parameter></entry>
<entry><parameter>resourceValue</parameter></entry>
<entry><parameter>resourceTypeName</parameter></entry>
<entry nameend="arg4" class="unused"/>
</row>
<row>
<entry>resource-free</entry>
<entry>Called when a resource is freed</entry>
<entry><parameter>resourceId</parameter></entry>
<entry><parameter>resourceTypeId</parameter></entry>
<entry><parameter>resourceValue</parameter></entry>
<entry><parameter>resourceTypeName</parameter></entry>
<entry nameend="arg4" class="unused"/>
</row>
</tbody>
</tgroup>
</table>
</para>
</sect1>
<sect1 id="arguments">
<title>Data Available in Probe Arguments</title>
<para>
To access data in arguments of type <type>string</type>, you will need
to use <ulink url="http://wikis.sun.com/display/DTrace/Actions+and+Subroutines#ActionsandSubroutines-{{copyinstr}}"><function>copyinstr()</function></ulink>.
To access data buffers referenced via <type>uintptr_t</type>'s, you will
need to use <ulink url="http://wikis.sun.com/display/DTrace/Actions+and+Subroutines#ActionsandSubroutines-{{copyin}}"><function>copyin()</function></ulink>.
<table id="Probe_Arguments">
<title>Probe Arguments</title>
<tgroup cols='3'>
<colspec colname="arg" colwidth="2*"/>
<colspec colname="type" colwidth="1*"/>
<colspec colname="desc" colwidth="7*"/>
<thead>
<row>
<entry>Argument name</entry>
<entry>Type</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><parameter>clientAddr</parameter></entry>
<entry><type>string</type></entry>
<entry>String representing address client connected from</entry>
</row>
<row>
<entry><parameter>clientFD</parameter></entry>
<entry><type>int</type></entry>
<entry>X server's file descriptor for server side of each connection</entry>
</row>
<row>
<entry><parameter>clientId</parameter></entry>
<entry><type>int</type></entry>
<entry>Unique integer identifier for each connection to the
X server</entry>
</row>
<row>
<entry><parameter>clientPid</parameter></entry>
<entry><type>pid_t</type></entry>
<entry>Process id of client, if connection is local
(from <function>getpeerucred()</function>)</entry>
</row>
<row>
<entry><parameter>clientZoneId</parameter></entry>
<entry><type>zoneid_t</type></entry>
<entry>Solaris: Zone id of client, if connection is local
(from <function>getpeerucred()</function>)</entry>
</row>
<row>
<entry><parameter>eventBuffer</parameter></entry>
<entry><type>uintptr_t</type></entry>
<entry>Pointer to buffer containing X event - decode using
structures in
<<ulink url="http://cgit.freedesktop.org/xorg/proto/xproto/tree/Xproto.h"><filename class="headerfile">X11/Xproto.h</filename></ulink>>
and similar headers for each extension</entry>
</row>
<row>
<entry><parameter>eventCode</parameter></entry>
<entry><type>uint8_t</type></entry>
<entry>Event number of X event</entry>
</row>
<row>
<entry><parameter>resourceId</parameter></entry>
<entry><type>uint32_t</type></entry>
<entry>X resource id (XID)</entry>
</row>
<row>
<entry><parameter>resourceTypeId</parameter></entry>
<entry><type>uint32_t</type></entry>
<entry>Resource type id</entry>
</row>
<row>
<entry><parameter>resourceTypeName</parameter></entry>
<entry><type>string</type></entry>
<entry>String representing X resource type
(<literal>"PIXMAP"</literal>, etc.)</entry>
</row>
<row>
<entry><parameter>resourceValue</parameter></entry>
<entry><type>uintptr_t</type></entry>
<entry>Pointer to data for X resource</entry>
</row>
<row>
<entry><parameter>resultCode</parameter></entry>
<entry><type>int</type></entry>
<entry>Integer code representing result status of request</entry>
</row>
<row>
<entry><parameter>requestBuffer</parameter></entry>
<entry><type>uintptr_t</type></entry>
<entry>Pointer to buffer containing X request - decode using
structures in
<<ulink url="http://cgit.freedesktop.org/xorg/proto/xproto/tree/Xproto.h"><filename class="headerfile">X11/Xproto.h</filename></ulink>>
and similar headers for each extension</entry>
</row>
<row>
<entry><parameter>requestCode</parameter></entry>
<entry><type>uint8_t</type></entry>
<entry>Request number of X request or Extension</entry>
</row>
<row>
<entry><parameter>requestName</parameter></entry>
<entry><type>string</type></entry>
<entry>Name of X request or Extension</entry>
</row>
<row>
<entry><parameter>requestLength</parameter></entry>
<entry><type>uint16_t</type></entry>
<entry>Length of X request</entry>
</row>
<row>
<entry><parameter>sequenceNumber</parameter></entry>
<entry><type>uint32_t</type></entry>
<entry>Number of X request in in this connection</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
</sect1>
<sect1 id="examples">
<title>Examples</title>
<example id="Counting_requests_by_request_name">
<title>Counting requests by request name</title>
<para>
This script simply increments a counter for each different request
made, and when you exit the script (such as by hitting
<keycombo action='simul'><keycap>Control</keycap><keycap>C</keycap>
</keycombo>) prints the counts.
<programlisting>
#!/usr/sbin/dtrace -s
Xserver*:::request-start
{
@counts[copyinstr(arg0)] = count();
}
</programlisting>
The output from a short run may appear as:
<screen>
QueryPointer 1
CreatePixmap 2
FreePixmap 2
PutImage 2
ChangeGC 10
CopyArea 10
CreateGC 14
FreeGC 14
RENDER 28
SetClipRectangles 40
</screen>
</para>
<para>
This can be rewritten slightly to cache the string containing the name
of the request since it will be reused many times, instead of copying
it over and over from the kernel:
<programlisting>
#!/usr/sbin/dtrace -s
string Xrequest[uintptr_t];
Xserver*:::request-start
/Xrequest[arg0] == ""/
{
Xrequest[arg0] = copyinstr(arg0);
}
Xserver*:::request-start
{
@counts[Xrequest[arg0]] = count();
}
</programlisting>
</para>
</example>
<example id="Get_average_CPU_time_per_request">
<title>Get average CPU time per request</title>
<para>This script records the CPU time used between the probes at
the start and end of each request and aggregates it per request type.
<programlisting>
#!/usr/sbin/dtrace -s
Xserver*:::request-start
{
reqstart = vtimestamp;
}
Xserver*:::request-done
{
@times[copyinstr(arg0)] = avg(vtimestamp - reqstart);
}
</programlisting>
The output from a sample run might look like:
<screen>
ChangeGC 889
MapWindow 907
SetClipRectangles 1319
PolyPoint 1413
PolySegment 1434
PolyRectangle 1828
FreeCursor 1895
FreeGC 1950
CreateGC 2244
FreePixmap 2246
GetInputFocus 2249
TranslateCoords 8508
QueryTree 8846
GetGeometry 9948
CreatePixmap 12111
AllowEvents 14090
GrabServer 14791
MIT-SCREEN-SAVER 16747
ConfigureWindow 22917
SetInputFocus 28521
PutImage 240841
</screen>
</para>
</example>
<example id="Monitoring_clients_that_connect_and_disconnect">
<title>Monitoring clients that connect and disconnect</title>
<para>
This script simply prints information about each client that
connects or disconnects from the server while it is running.
Since the provider is specified as <code>Xserver$1</code> instead
of <code>Xserver*</code> like previous examples, it won't monitor
all Xserver processes running on the machine, but instead expects
the process id of the X server to monitor to be specified as the
argument to the script.
<programlisting>
#!/usr/sbin/dtrace -s
Xserver$1:::client-connect
{
printf("** Client Connect: id %d\n", arg0);
}
Xserver$1:::client-auth
{
printf("** Client auth'ed: id %d => %s pid %d\n",
arg0, copyinstr(arg1), arg2);
}
Xserver$1:::client-disconnect
{
printf("** Client Disconnect: id %d\n", arg0);
}
</programlisting>
A sample run:
<screen>
<prompt>#</prompt> <userinput>./foo.d 5790</userinput>
<computeroutput>dtrace: script './foo.d' matched 4 probes
CPU ID FUNCTION:NAME
0 15774 CloseDownClient:client-disconnect ** Client Disconnect: id 65
2 15774 CloseDownClient:client-disconnect ** Client Disconnect: id 64
0 15773 EstablishNewConnections:client-connect ** Client Connect: id 64
0 15772 AuthAudit:client-auth ** Client auth'ed: id 64 => local host pid 2034
0 15773 EstablishNewConnections:client-connect ** Client Connect: id 65
0 15772 AuthAudit:client-auth ** Client auth'ed: id 65 => local host pid 2034
0 15774 CloseDownClient:client-disconnect ** Client Disconnect: id 64
</computeroutput>
</screen>
</para>
</example>
<example id="Monitoring_clients_creating_Pixmaps">
<title>Monitoring clients creating Pixmaps</title>
<para>
This script can be used to determine which clients are creating
pixmaps in the X server, printing information about each client
as it connects to help trace it back to the program on the other
end of the X connection.
<programlisting>
#!/usr/sbin/dtrace -qs
string Xrequest[uintptr_t];
string Xrestype[uintptr_t];
Xserver$1:::request-start
/Xrequest[arg0] == ""/
{
Xrequest[arg0] = copyinstr(arg0);
}
Xserver$1:::resource-alloc
/arg3 != 0 && Xrestype[arg3] == ""/
{
Xrestype[arg3] = copyinstr(arg3);
}
Xserver$1:::request-start
/Xrequest[arg0] == "X_CreatePixmap"/
{
printf("-> %s: client %d\n", Xrequest[arg0], arg3);
}
Xserver$1:::request-done
/Xrequest[arg0] == "X_CreatePixmap"/
{
printf("<- %s: client %d\n", Xrequest[arg0], arg3);
}
Xserver$1:::resource-alloc
/Xrestype[arg3] == "PIXMAP"/
{
printf("** Pixmap alloc: %08x\n", arg0);
}
Xserver$1:::resource-free
/Xrestype[arg3] == "PIXMAP"/
{
printf("** Pixmap free: %08x\n", arg0);
}
Xserver$1:::client-connect
{
printf("** Client Connect: id %d\n", arg0);
}
Xserver$1:::client-auth
{
printf("** Client auth'ed: id %d => %s pid %d\n",
arg0, copyinstr(arg1), arg2);
}
Xserver$1:::client-disconnect
{
printf("** Client Disconnect: id %d\n", arg0);
}
</programlisting>
Sample output from a run of this script:
<screen><computeroutput>
** Client Connect: id 17
** Client auth'ed: id 17 => local host pid 20273
-> X_CreatePixmap: client 17
** Pixmap alloc: 02200009
<- X_CreatePixmap: client 17
-> X_CreatePixmap: client 15
** Pixmap alloc: 01e00180
<- X_CreatePixmap: client 15
-> X_CreatePixmap: client 15
** Pixmap alloc: 01e00181
<- X_CreatePixmap: client 15
-> X_CreatePixmap: client 14
** Pixmap alloc: 01c004c8
<- X_CreatePixmap: client 14
** Pixmap free: 02200009
** Client Disconnect: id 17
** Pixmap free: 01e00180
** Pixmap free: 01e00181
</computeroutput></screen>
</para>
</example>
</sect1>
</article>