[dtrace-discuss] Dtrace compiler performance

[CHIAN-PHON LIN]

Hi,

Running a Dtrace program with simple probe pattern:

fbt:genunix::entry

got

dtrace: script 'cc.d' matched 5953 probes

in ONE second.

However, running with 100 probe patterns such as:

fbt:genunix:calcloadavg:entry,
fbt:genunix:delay_wakeup:entry,
fbt:genunix:deadman:entry,
fbt:genunix:deadman_online:entry,
fbt:genunix:clock_highres_settime:entry,
  ..
  ..
<100 of them>

got

dtrace: script 'cc.d' matched 100 probes

in about TEN seconds.

I also try 200 probes and got about 20 seconds.
So, it appears to be proportional to the number
of probe patterns.

My question is:
Why enabling 2% of the probes in a module takes
10 time longer than enabling the entire module?

BTW, people might want to ask why I am doing this.
It is because I am developing a test coverage
tool which allow user to define their own tracing
scope.  For instance, user might want to select
600 probes in genunix as tracing scope and ends
up waiting for one minute before they could run
their applications or test programs.  This may
not be acceptable to the user.

Thanks.

************************************************
* C P Lin, Common Technology Project Lead.     *
* Sun Microsystems Inc.                        *
* E-Mail:  c.lin at sun.com                       *
* Address: 4150 Network Circle, M/S UMPK12-330 *
* Santa Clara, CA 95054                        *
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