Comment 6 for bug 2025647

Something that quickly gave me the libc realloc calls including their size argument but at relatively low overhead was:

$ git clone https://github.com/brendangregg/perf-tools.git
$ cd perf-tools
$ sudo chmod +x /lib/x86_64-linux-gnu/libc.so.6
$ sudo ./bin/uprobe -H 'p:libc:realloc %di %si' | grep libvirtd

# you could do similar with perf trace looking at brk/mmap
$ sudo apt install linux-tools-common linux-tools-generic
$ perf trace

You might need to modify this to your needs, e.g. restrict the PID/Thread to your libvirt instead of grep (have a look with the above first how/if pids fluctuate throughout your load).