Hi!
tst_pollute_memory() consume time is proportional to the amount of free RAM, it is hard to find one fixed value of max_runtime to fit all test platforms.
From my experience, if you limited this test only run with small machine (e.g. RAM <= 32G), that performs well with whatever bare metal or VM, no timeout ever.
Btw, we did that by setting a test filter before LTP running, also we could add a field .max_mem_avail to tst_test struct for achieving that, but not sure if it's worth doing that at this moment.
The proper solution will be adding a separate timeouts for setup/cleanup and limiting the setup runtime to something sensible, but that is something for the next development cycle.