Re: malloc() tracing in perf?

[Pekka Enberg]

Pekka Enberg wrote:
> Hi Peter,
>
> On Thu, 2009-08-06 at 10:48 +0300, Pekka Enberg wrote:
> > > Hi,
> > >
> > > It's me again :-).
> > >
> > > I have a little user-space application that is pretty memory hungry 
> > > and I want to understand why. I started to google around for a memory 
> > > profiler or a malloc() tracer but didn't seem to find anything really 
> > > useful.
> > >
> > > But then it hit me, why can't I have kmemtrace + perf but for 
> > > user-space? Something like the "Malloc Trace" shown here:
> > >
> > > http://developer.apple.com/documentation/developertools/conceptual/SharkUserGuide/OtherProfilingandTracingTechniques/OtherProfilingandTracingTechniques.html#//apple_ref/doc/uid/TP40005233-CH6-SW17 
> > >
> > >
> > > Does this sound like something that could/should be part of "perf"? 
> > > How would all this work anyway? Can we intercept malloc() and free() 
> > > somehow? Where would the data be pushed? Am I just going perf-crazy 
> > > and trying to turn it into a swiss army knife because it's so easy to 
> > > use?-)
>
> Peter Zijlstra wrote:
> > OK, you just trod into a wasp's nest :-)
> >
> > That sounds like uprobes, the equivalent of kprobes but for userspace.
> >
> > I seem to have heard people are working on such a thing, but I can't
> > seem to find a single LKML post with 'uprobe' in the subject in the past
> > two years or something (except for MTUprobe) -- so I guess its not
> > really going anywhere any fast.
>
> [snip]
>
> Right. Are dynamic tracepoints what we want for malloc() and free() 
> interception, though? I guess we can just do generic "userspace function 
> called" events and record the passed parameters. Then "perf memreport" 
> can just go find all the malloc() and free() calls and construct a 
> memory profile out of it?
>
> That said, I'd also be interested in wiring my userspace VM garbage 
> collector to emit similar alloc and free events as well (because perf 
> already has a JIT symbol map) which makes me think we want generic 
> "userspace allocated memory" events.

Argh, I dropped LKML from the CC. Sorry for the duplicate email!

			Pekka
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