Sean, thanks for the pointer. This was actually super helpful because in the Apple dtrace tarball there's a port of the dtrace toolkit; these examples are going to answer a lot of questions.
On Mon, Mar 31, 2008 at 12:17 AM, Sean McGrath - Sun Microsystems Ireland <[EMAIL PROTECTED]> wrote: > Travis Crawford stated: > > < Thanks Menno and Jim! I'm looking around the Apple documentation to > < hopefully find where they store the load average. Yes, it would be > < nice to have all the source available; I should take a better look at > < opensolaris. > > Why not browse the Apple port of The DTraceToolkit itself ? > > It uses averunnable.ldavg instead of the Solaris specific hp_avenrun. > Found from having a look at the OS-X port of DTrace at: > http://www.opensource.apple.com/darwinsource > > Regards, > Sean. > > > . > < > < --travis > < > < > < On Mon, Mar 31, 2008 at 12:02 AM, Jim Mauro <[EMAIL PROTECTED]> wrote: > < > Hi Travis - Your first clue here is the backtick operator (`) used to > < > extract hp_avenrun[0]. The backtick operator is used to read the > < > value of kernel variables, which will be specific to the running kernel. > < > That is, Solaris, Mac OS X (Darwin), FreeBSD and all other kernels > < > with DTrace will not have portability when it comes to dtrace scripts > < > that use the backtick variable, since by definition they will be kernel > < > specific. > < > > < > hp_avenrun[] is a Solaris kernel variable: > < > > < > > http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/os/clock.c#97 > < > > < > For some kernel variables (like avenrun), you could look around for > < > something > < > similar in your target kernel: > < > > < > kilroy> nm -x /mach_kernel | grep avenrun > < > 004d25ac 0f 08 0000 0002dbb9 _avenrun > < > kilroy> > < > > < > Of course, without the source, it's not clear what the variable type > is.... > < > > < > So....your example below is specific to Solaris. If you see the backtick > < > operator, think "kernel specific". > < > > < > HTH, > < > /jim > < > > < > > < > > < > Travis Crawford wrote: > < > > Hi dtrace-discuss, > < > > > < > > Having recently upgraded to OS X 10.5 I'm relatively new to DTrace, so > < > > apologies if this has been covered before; I did search the archives > < > > and didn't find anything though. > < > > > < > > As a DTrace starter project I'd like to understand how to extract > < > > common performance metrics before diving too far in. One of these > < > > common metrics is load average, which I thought would be pretty easy. > < > > However, I'm confused by this code snippet (from > < > > http://www.brendangregg.com/DTrace/iotop): > < > > > < > > """ > < > > /* fetch 1 min load average */ > < > > this->load1a = `hp_avenrun[0] / 65536; > < > > this->load1b = ((`hp_avenrun[0] % 65536) * 100) / 65536; > < > > """ > < > > > < > > I can't figure out where hp_avenrun is defined. I searched > < > > http://wikis.sun.com/display/DTrace as well as looking at all the > < > > probes on my system ($ sudo dtrace -l | grep hp_avenrun) and came up > < > > empty. > < > > > < > > So my question is, when reading d scripts, how should I go about > < > > finding out what these mysterious variables are? > < > > > < > > Thanks, > < > > Travis > < > > _______________________________________________ > < > > dtrace-discuss mailing list > < > > [email protected] > < > > > < > > < _______________________________________________ > < dtrace-discuss mailing list > < [email protected] > > -- > Sean. > . > _______________________________________________ dtrace-discuss mailing list [email protected]
