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Re: [PATCH v3] Tracepoint Tapset for Memory Subsystem
- From: Rajasekhar Duddu <rajduddu at linux dot vnet dot ibm dot com>
- To: "Frank Ch. Eigler" <fche at redhat dot com>
- Cc: systemtap at sources dot redhat dot com
- Date: Fri, 9 Oct 2009 22:38:05 +0530
- Subject: Re: [PATCH v3] Tracepoint Tapset for Memory Subsystem
- References: <4AB90BE0.4030405@redhat.com> <y0mmy4mishg.fsf@fche.csb> <4AB94A1B.4090801@redhat.com> <20090924180817.GA9698@rajduddu> <4ABD3B2B.4020107@redhat.com> <20090930101156.GA3792@rajduddu> <20091002151344.GA9516@rajduddu> <y0mocokgxe2.fsf@fche.csb> <20091007130728.GA6574@rajduddu> <y0mk4z7gez8.fsf@fche.csb>
On Wed, Oct 07, 2009 at 03:51:07PM -0400, Frank Ch. Eigler wrote:
> Rajasekhar Duddu <rajduddu@linux.vnet.ibm.com> writes:
>
> > [...]
> >> Nice. I thought that the raison d'etre for these aliases was to
> >> abstract the presence or absence of tracepoints, so is there no
> >> fallback kprobe available? Something like this:
> >>
> > Fallback kprobe is not available for other memory functions because
> > the variables exported by them are will be modified.
>
> Could you elaborate? Do you mean that the same values may not be
> available from a kprobe context?
>
>
Hi Frank,
Yes, the same values may not be available from a kprobe
context, for example if we take "ret" variable as it is populated mid-way in
the function and it is also the return value of a function which can
be captured only by a return probe. But by a return probe we cannot
capture the formal parameters of the memory function.
Thanks
--
Rajasekhar Duddu (rajduddu@linux.vnet.ibm.com),
Linux on System z - CSVT, IBM LTC, Bangalore.