Why RSS is much bigger than GC live?

I used the function mentioned herehttps://discourse.julialang.org/t/how-to-track-total-memory-usage-of-julia-process-over-time/91167/2, meminfo_julia() and meminfo_procfs() to get RSS and GC_live memory, but I found my program have much bigger RSS memory than GC_live, I don’t know why.

1    RSS:       16651.820 MiB        GC live:    5026.047 MiB        Max. RSS:  47895.031 MiB
2    RSS:       16658.062 MiB        GC live:    5054.207 MiB        Max. RSS:  47895.031 MiB
3    RSS:       17807.227 MiB        GC live:   11322.439 MiB        Max. RSS:  47895.031 MiB
4    RSS:       34378.992 MiB        GC live:    5388.977 MiB        Max. RSS:  52125.352 MiB

Above is some output during the program.
Are there useful tools that I can use to optimize my program? my program is easy to outofmemory, but actually I didn’t save so much objects.