mirek wrote on Mon, 24 June 2019 03:22

Based on this, I do not see any defect or deficiency, except the choosen one (keep the memory).

Well, I do not think that taking from the system 4.6Gb when the app is allocating ~400Mb is acceptable.
Default behavior of glibc's allocator is optimized for huge enterprise-level apps, but with some manual tweaking it performs fine with small apps. jemalloc would perform even better, I believe.