File:  [NetBSD Developer Wiki] / wikisrc / tutorials / how_to_enable_and_run_dtrace.mdwn
Revision 1.4: download - view: text, annotated - select for diffs
Mon Nov 4 02:50:01 2013 UTC (5 months, 2 weeks ago) by wiki
Branches: MAIN
CVS tags: HEAD
web commit by mspo: make links go somewhere

DTrace is a Dynamic Tracing framework developed by Sun and ported to NetBSD. It enables extensive instrumentation of the kernel and user space. See the [DTrace Community Page](http://dtrace.org) for more information. Also see [DTrace Introduction](http://dtrace.org/guide/preface.html). 


DTrace is a work-in-progress effort and it is for x86 systems only currently (there is some arm support but it is completely untested). Two providers are available; the Statically Defined Tracing (SDT) provider and the Function Boundary Tracer (FBT) provider. 

You can currently run a hello world DScript. 

##  Building DTrace 

You need the following options in your kernel: 
    
    options         INSECURE
    options         KDTRACE_HOOKS   # DTrace support
    options         MODULAR
    

You also need to build distribution with the options MKMODULAR=yes and MKDTRACE=yes. 

##  Running hello world 

Load the solaris and dtrace modules, and the SDT (Statically Defined Tracing) and FBT (Function Boundary Tracing) modules: 
    
    modload solaris
    modload dtrace
    modload sdt
    modload fbt
    

Make the dtrace device node: 
    
    mkdir /dev/dtrace
    mknod /dev/dtrace/dtrace c dtrace 0
    

List the dtrace probes 
    
    dtrace -l
    
       ID   PROVIDER            MODULE                          FUNCTION NAME
        1     dtrace                                                     BEGIN
        2     dtrace                                                     END
        3     dtrace                                                     ERROR
        4        fbt            netbsd             AcpiAcquireGlobalLock entry
        5        fbt            netbsd             AcpiAcquireGlobalLock return
        6        fbt            netbsd             AcpiAllocateRootTable entry
        7        fbt            netbsd                    AcpiAttachData entry
        . 
        .
    29129        fbt           solaris                   zfs_vop_getattr entry 
    29130        fbt           solaris                   zfs_vop_getattr return
    29131       proc                                                     create
    29132       proc                                                     exec 
        .
        .
    29140       proc                                                     lwp_start
    29141       proc                                                     lwp_exit
    

  


Put the following into the file hello.d 
    
    BEGIN
    {
        trace("Hello world");
        exit(0);
    }
    

Run the hello world script: 
    
    dtrace -s hello.d
    
    dtrace: script './hello.d' matched 1 probe
    CPU     ID                    FUNCTION:NAME
      0      1                           :BEGIN   Hello world
    

A more complex example that traces the execution of a sleep operation in the kernel: 
    
    #pragma D option flowindent
    
    fbt::syscall:entry
    /execname == "sleep" && guard++ == 0/
    {
            self->traceme = 1;
            printf("fd: %d", arg0);
    }
    
    fbt:::
    /self->traceme/
    {}
    
    fbt::syscall:return
    /self->traceme/
    {
            self->traceme = 0;
            exit(0);
    }
    

Start the script running (dtrace -s <scriptname.d>) and then execute a sleep 2 in another shell. 


CVSweb for NetBSD wikisrc <wikimaster@NetBSD.org> software: FreeBSD-CVSweb