Xserver Provider for DTrace Alan Coopersmith Oracle Corporation Solaris Engineering X Server Version 1.12.2 Copyright © 2005, 2006, 2007, 2010 Oracle and/or its affiliates. All rights reserved. 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: The above copyright notice and this permission notice (including the next paragraph) shall be included in all copies or substantial portions of the Software. 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. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Table of Contents Introduction Available probes Data Available in Probe Arguments Examples Introduction This page provides details on a statically defined user application tracing provider for the DTrace facility in Solaris™ 10, MacOS X™ 10.5, and later releases. This provider instruments various points in the X server, to allow tracing what client applications are up to. 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. 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. Available probes Due to the way User-Defined DTrace probes work, arguments to these probes all bear undistinguished names of arg0, arg1, arg2, etc. These tables should help you determine what the real data is for each of the probe arguments. Table 1. Probes and their arguments ┌─────────────────┬─────────────┬───────────┬──────────────┬──────────────┬────────────────┬─────────────┐ │ Probe name │ Description │ arg0 │ arg1 │ arg2 │ arg3 │ arg4 │ ├─────────────────┴─────────────┴───────────┴──────────────┴──────────────┴────────────────┴─────────────┤ │Request Probes │ ├─────────────────┬─────────────┬───────────┬──────────────┬──────────────┬────────────────┬─────────────┤ │ │Called just │ │ │ │ │ │ │ │before │ │ │ │ │ │ │request-start │processing │requestName│requestCode │requestLength │clientId │requestBuffer│ │ │each client │ │ │ │ │ │ │ │request. │ │ │ │ │ │ ├─────────────────┼─────────────┼───────────┼──────────────┼──────────────┼────────────────┼─────────────┤ │ │Called just │ │ │ │ │ │ │ │after │ │ │ │ │ │ │request-done │processing │requestName│requestCode │sequenceNumber│clientId │resultCode │ │ │each client │ │ │ │ │ │ │ │request. │ │ │ │ │ │ ├─────────────────┴─────────────┴───────────┴──────────────┴──────────────┴────────────────┴─────────────┤ │Event Probes │ ├─────────────────┬─────────────┬───────────┬──────────────┬──────────────┬────────────────┬─────────────┤ │ │Called just │ │ │ │ │ │ │send-event │before send │clientId │eventCode │eventBuffer │  │  │ │ │each event to│ │ │ │ │ │ │ │a client. │ │ │ │ │ │ ├─────────────────┴─────────────┴───────────┴──────────────┴──────────────┴────────────────┴─────────────┤ │Client Connection Probes │ ├─────────────────┬─────────────┬───────────┬──────────────┬──────────────┬────────────────┬─────────────┤ │ │Called when a│ │ │ │ │ │ │ │new │ │ │ │ │ │ │client-connect │connection is│clientId │clientFD │  │  │  │ │ │opened from a│ │ │ │ │ │ │ │client │ │ │ │ │ │ ├─────────────────┼─────────────┼───────────┼──────────────┼──────────────┼────────────────┼─────────────┤ │ │Called when │ │ │ │ │ │ │ │client │ │ │ │ │ │ │ │authenticates│ │ │ │ │ │ │client-auth │(normally │clientId │clientAddr │clientPid │clientZoneId │  │ │ │just after │ │ │ │ │ │ │ │connection │ │ │ │ │ │ │ │opened) │ │ │ │ │ │ ├─────────────────┼─────────────┼───────────┼──────────────┼──────────────┼────────────────┼─────────────┤ │ │Called when a│ │ │ │ │ │ │client-disconnect│client │clientId │  │  │  │  │ │ │connection is│ │ │ │ │ │ │ │closed │ │ │ │ │ │ ├─────────────────┴─────────────┴───────────┴──────────────┴──────────────┴────────────────┴─────────────┤ │Resource Allocation Probes │ ├─────────────────┬─────────────┬───────────┬──────────────┬──────────────┬────────────────┬─────────────┤ │ │Called when a│ │ │ │ │ │ │ │new resource │ │ │ │ │ │ │resource-alloc │(pixmap, gc, │resourceId │resourceTypeId│resourceValue │resourceTypeName│  │ │ │colormap, │ │ │ │ │ │ │ │etc.) is │ │ │ │ │ │ │ │allocated │ │ │ │ │ │ ├─────────────────┼─────────────┼───────────┼──────────────┼──────────────┼────────────────┼─────────────┤ │ │Called when a│ │ │ │ │ │ │resource-free │resource is │resourceId │resourceTypeId│resourceValue │resourceTypeName│  │ │ │freed │ │ │ │ │ │ └─────────────────┴─────────────┴───────────┴──────────────┴──────────────┴────────────────┴─────────────┘ Data Available in Probe Arguments To access data in arguments of type string, you will need to use copyinstr(). To access data buffers referenced via uintptr_t's, you will need to use copyin (). Table 2. Probe Arguments ┌────────────────┬─────────┬──────────────────────────────────────────────────┐ │ Argument name │ Type │ Description │ ├────────────────┼─────────┼──────────────────────────────────────────────────┤ │clientAddr │string │String representing address client connected from │ ├────────────────┼─────────┼──────────────────────────────────────────────────┤ │clientFD │int │X server's file descriptor for server side of each│ │ │ │connection │ ├────────────────┼─────────┼──────────────────────────────────────────────────┤ │clientId │int │Unique integer identifier for each connection to │ │ │ │the X server │ ├────────────────┼─────────┼──────────────────────────────────────────────────┤ │clientPid │pid_t │Process id of client, if connection is local (from│ │ │ │getpeerucred()) │ ├────────────────┼─────────┼──────────────────────────────────────────────────┤ │clientZoneId │zoneid_t │Solaris: Zone id of client, if connection is local│ │ │ │(from getpeerucred()) │ ├────────────────┼─────────┼──────────────────────────────────────────────────┤ │ │ │Pointer to buffer containing X event - decode │ │eventBuffer │uintptr_t│using structures in and similar │ │ │ │headers for each extension │ ├────────────────┼─────────┼──────────────────────────────────────────────────┤ │eventCode │uint8_t │Event number of X event │ ├────────────────┼─────────┼──────────────────────────────────────────────────┤ │resourceId │uint32_t │X resource id (XID) │ ├────────────────┼─────────┼──────────────────────────────────────────────────┤ │resourceTypeId │uint32_t │Resource type id │ ├────────────────┼─────────┼──────────────────────────────────────────────────┤ │resourceTypeName│string │String representing X resource type ("PIXMAP", │ │ │ │etc.) │ ├────────────────┼─────────┼──────────────────────────────────────────────────┤ │resourceValue │uintptr_t│Pointer to data for X resource │ ├────────────────┼─────────┼──────────────────────────────────────────────────┤ │resultCode │int │Integer code representing result status of request│ ├────────────────┼─────────┼──────────────────────────────────────────────────┤ │ │ │Pointer to buffer containing X request - decode │ │requestBuffer │uintptr_t│using structures in and similar │ │ │ │headers for each extension │ ├────────────────┼─────────┼──────────────────────────────────────────────────┤ │requestCode │uint8_t │Request number of X request or Extension │ ├────────────────┼─────────┼──────────────────────────────────────────────────┤ │requestName │string │Name of X request or Extension │ ├────────────────┼─────────┼──────────────────────────────────────────────────┤ │requestLength │uint16_t │Length of X request │ ├────────────────┼─────────┼──────────────────────────────────────────────────┤ │sequenceNumber │uint32_t │Number of X request in in this connection │ └────────────────┴─────────┴──────────────────────────────────────────────────┘ Examples Example 1. Counting requests by request name This script simply increments a counter for each different request made, and when you exit the script (such as by hitting Control+C) prints the counts. #!/usr/sbin/dtrace -s Xserver*:::request-start { @counts[copyinstr(arg0)] = count(); } The output from a short run may appear as: QueryPointer 1 CreatePixmap 2 FreePixmap 2 PutImage 2 ChangeGC 10 CopyArea 10 CreateGC 14 FreeGC 14 RENDER 28 SetClipRectangles 40 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: #!/usr/sbin/dtrace -s string Xrequest[uintptr_t]; Xserver*:::request-start /Xrequest[arg0] == ""/ { Xrequest[arg0] = copyinstr(arg0); } Xserver*:::request-start { @counts[Xrequest[arg0]] = count(); } Example 2. Get average CPU time per request This script records the CPU time used between the probes at the start and end of each request and aggregates it per request type. #!/usr/sbin/dtrace -s Xserver*:::request-start { reqstart = vtimestamp; } Xserver*:::request-done { @times[copyinstr(arg0)] = avg(vtimestamp - reqstart); } The output from a sample run might look like: 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 Example 3. Monitoring clients that connect and disconnect 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 Xserver$1 instead of Xserver* 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. #!/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); } A sample run: # ./foo.d 5790 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 Example 4. Monitoring clients creating Pixmaps 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. #!/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); } Sample output from a run of this script: ** 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