Re: [Valgrind-users] Pre-instrumented vs JIT instrumentation

[Mike B. <mbr...@vi...>]

Perhaps I misunderstand how valgrind works.  I have the understanding that,
using the synthetic CPU, valgrind instruments the application on the fly and
stores the instrumented code blocks in a cache.  The author describes this
process here http://developer.kde.org/~sewardj/docs-1.9.5/mc_techdocs.html.

Do I misunderstand?

Note that Quanitfy for Windows does not require a relink.  You just point it
at an executable and off it goes.  First it instruments the executable and
dependent DLLs and then it executes it.  The UNIX version requires a
relink - or at least it did when I last used it in the mid-1990's on HPUX.

Mike Bresnahan
----- Original Message ----- 
From: "Alex Ivershen" <ale...@in...>
To: "Mike Bresnahan" <mbr...@vi...>
Cc: <Val...@li...>
Sent: Thursday, June 05, 2003 5:41 PM
Subject: Re: [Valgrind-users] Pre-instrumented vs JIT instrumentation


> Valgrind, unlike Rational suite tools, does not "instrument" anything.
That's the beauty of it - you don't need to recompile (or in case ot
Quantify re-link) the application.  The difference is that Rational tools
embed extra code inside your object files and libraries - for memory or
performance profiling. As a result, executable size, shared libraries sizes
are huge and executiion suffers greatly (esp. with purify). Valgrind, on the
other hand, runs your application on a synthetic CPU, all the machine
instructions of your app are executed by Valgrind on this CPU and
memory/performance profiling is done there, not in your app code.  As far as
Quantify comparison, cachegrind sking gives you much more information - e.g.
Quantify does not report cache usage profile.
> Last but not least - Valgrind is free, has MUCH better developer support,
and is updated more frequently.
> Downside - only runs on x86 Linux, exactly because of synthetic CPU -
porting it to other platforms is too much work, so developers chose the most
popular platform.
>
> Regards,
> Alex