From: fche@redhat.com (Frank Ch. Eigler)
To: Guang Lei Li <liguangl@cn.ibm.com>
Cc: systemtap@sources.redhat.com
Subject: Re: adding statements in alias definition as epilogue
Date: Wed, 05 Apr 2006 12:03:00 -0000 [thread overview]
Message-ID: <y0m4q18rzzo.fsf@ton.toronto.redhat.com> (raw)
In-Reply-To: <OFC1F2C5D4.A0F684D7-ON48257147.000F0756-48257147.000F2A0A@cn.ibm.com>
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.
> > This assumes that per-probe backtrace configuration makes more sense
> > than, say, a single global variable.
>
> 'backtrace' used inside the probe definitions is a local variable, which
> is cheaper than using a global variable.
Only slightly (one extra shared lock).
> 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?
> [...] 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.
- FChE
next prev parent reply other threads:[~2006-04-05 12:03 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 [this message]
2006-04-05 16:06 ` Guang Lei Li
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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