From: Guang Lei Li <liguangl@cn.ibm.com>
To: systemtap@sources.redhat.com
Cc: fche@redhat.com
Subject: Re: adding statements in alias definition as epilogue
Date: Wed, 05 Apr 2006 02:46:00 -0000 [thread overview]
Message-ID: <OFC1F2C5D4.A0F684D7-ON48257147.000F0756-48257147.000F2A0A@cn.ibm.com> (raw)
In-Reply-To: <20060405012447.GC16498@redhat.com>
> OK, how about forking it into independent twins?
>
> probe addevent.tskdispatch.cpuidle = kernel.inline("idle_balance") {
> log_cpuidle_tracedata(HOOKID_TASK_CPUIDLE, 0)
> }
> probe addevent.tskdispatch.cpuidle.backtrace =
kernel.inline("idle_balance") {
> log_cpuidle_tracedata(HOOKID_TASK_CPUIDLE, 1)
> }
>
I ever thought abut doing like this. But the biggest problem of it is not
only the redundant codes, but it will have trouble if you use wildcard(*)
to specify a group of hooks, for example:
probe addevent.tskdispatching.* {}
will cause both addevent.tskdispatch.cpuidle.backtrace &
addevent.tskdispatch.cpuidle to be triggered.
> 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. And it also enables to turn
on/off backtrace for each event separately instead of turn on/off all
backtraces as a whole.
>
> It still seems like a big step to introduce this inverted data/control
> flow. We would have to consider composing multiple levels of aliases,
> to make sure a programmer and a user can reason easily about what
> should happen.
>
> - FChE
Yes. Maybe some syntax for specifying different kinds of aliases need to
be introduced.
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
}
- Li Guanglei
next prev parent reply other threads:[~2006-04-05 2:46 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 [this message]
2006-04-05 12:03 ` Frank Ch. Eigler
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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