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Re: Cross instrumentation with user space tracing enabled
- From: fche at redhat dot com (Frank Ch. Eigler)
- To: h patel <hpatel05 at gmail dot com>
- Cc: systemtap at sources dot redhat dot com
- Date: Mon, 06 Dec 2010 16:59:20 -0500
- Subject: Re: Cross instrumentation with user space tracing enabled
- References: <AANLkTinVz6jb+rXMsYJOq6UGvqry2hi1Qz926vZitSj4@mail.gmail.com>
Hi -
hpatel05 wrote:
> [...]
> My setup is one of the most complex use case for systemtap :)
> - Cross Instrumentation with user space trace support required.
> - Host : Running CentOS 5.4 with 2.6.18-164.el5 i686
> - Target : Self compiled Kernel 2.6.32.10 i686, image size max 512 mb.
Sounds fine.
> My queries are as follows :
> 1) I was able to run normal kernel scripts successfully on target, but
> user space script is having issue.. [...]
You found the uprobes.ko bit. git systemtap contains a fix to the
client/server code to automate this aspect too.
> 2) Is it possible to use for Systemtap without debuginfo ? e.g. Only
> with Kernel Markers support and User space traces enabled.
Kernel markers & tracepoints don't require kernel-debuginfo on the
systemtap compile (host) side. Modern user-space markers (sys/sdt.h)
usually don't require userspace debuginfo either. General user-space
probes may require userspace debuginfo (for the probed processes).
> As of now, I am working the long way of keeping debuginfo for target
> on Host box itself, I can't afford debuginfo on target as it goes
> beyond max image size.
Of course. None of this is needed on the target.
> 3) This is with performance related. Pardon my kernel knowledge. How
> the dynamic filtering of traces actually works?
Each kernel & user-space marker/tracepoint is individually controlled.
Only those you attach to with live stap scripts represent any run-time
overhead.
- FChE