[Valgrind-developers] How can I improve the performance of my memcheck customization?

[Enzo B. <enz...@gm...>]

Hello,

For my computer science thesis, I need to instrument programs in order to
know which floating point values are being stored to buffers whose size is
greater than a certain threshold. For doing that, I modified the tool
memcheck in this public repository
<https://github.com/enzobonansea/floating-point-vectors-inspector>; you can
find my modifications by searching for "memlog" in the code.

The customization works as I expect, giving me the floating point values
that I need. Now, I want to optimize my code since it's CPU intensive and
makes the instrumented applications too slow. For instance, I ran the
memcheck customization against the SPEC2017 tool called lbm which took
originally a few seconds to run, but under the tool it takes more than 2
minutes with the CPU at 100% all the time.

If you see the code, the cause of the performance degradation is evident:
for every store I'm calling the dirty helper log_store, which means that
I'm calling that C function millions of times.

I used Valgrind's memcheck several times as a user, but 2 months ago was my
first time seeing the tool's source code. So, since I'm new on this and you
guys have a lot of experience working on the project, maybe you find my
problem trivial and you can have a good idea of how I can improve the
performance of my customization of memcheck.

Any ideas will be welcomed, thanks!