From: Guang Lei Li <liguangl@cn.ibm.com>
To: fche@redhat.com (Frank Ch. Eigler)
Cc: systemtap@sources.redhat.com
Subject: Re: adding statements in alias definition as epilogue
Date: Wed, 05 Apr 2006 16:06:00 -0000 [thread overview]
Message-ID: <OF9B1B05B9.D8056397-ON48257147.0056BDE4-48257147.00587928@cn.ibm.com> (raw)
In-Reply-To: <y0m4q18rzzo.fsf@ton.toronto.redhat.com>
systemtap-owner@sourceware.org wrote on 2006-04-05 20:03:23:
> Guang Lei Li <liguangl@cn.ibm.com> writes:
>
> > [...]
> > probe addevent.tskdispatching.* {}
> >
> > will cause both addevent.tskdispatch.cpuidle.backtrace &
> > addevent.tskdispatch.cpuidle to be triggered.
>
> Actually, it doesn't: the wildcard only consumes one component of the
> probe point name.
I tried, and found:
probe addevent.tskdispatching.* = probe addevent.tskdispatching.cpuidle
but addevent.tskdispatching.cpuidle.backtrace is removed away from the
generated probes.
>
> > And it also enables to turn on/off backtrace for each event
> > separately instead of turn on/off all backtraces as a whole.
>
> I see that, but is this capability important & useful? Plus, apropos
> an earlier message, how does the concept of high-performance binary
> tracing mesh at all with slow and bulky backtrace generation?
>
Because current backtrace printing is costly, so I want to let the user to
only turn on backtrace for those events necessary.
But you are right, backtrace printing is too slow, we need a faster way of
getting the backtrace
>
> > [...] Besides my specific need of alias definition as epilogue, I
> > think it is also useful if you want a filter: [...]
> >
> > probe derived_probe := alias_with_filter_codes {
> > filter_on = 1
> > scsi_lun = 2
> > scsi_dev_major = 3
> > }
>
> This style of usage could be accommodated with explicit code
> (analogous to "if (target() != pid()) next") instead of alias epilogues.
It is only suitable for filtering by pid, which provides a way of passing
in the target pid by "stap -c cmd" or "stap -x targetid". But how can you
pass in filter_on, scsi_lun & scsi_dev_major? The newly arguments support
in stap could make it, but it seems not a good solution in this example.
>
>
> - FChE
next prev parent reply other threads:[~2006-04-05 16:06 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-04-05 0:41 Guang Lei Li
2006-04-05 1:24 ` Frank Ch. Eigler
2006-04-05 2:46 ` Guang Lei Li
2006-04-05 12:03 ` Frank Ch. Eigler
2006-04-05 16:06 ` Guang Lei Li [this message]
2006-04-05 20:16 ` Frank Ch. Eigler
-- strict thread matches above, loose matches on Subject: below --
2006-04-03 9:25 Li Guanglei
2006-04-03 9:59 ` bibo,mao
2006-04-03 16:00 ` Frank Ch. Eigler
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