Ram usage way higher in 17.04.1 than openwrt 15.05

I notice this differnce:

17.01.4:

VmallocTotal: 1048372 kB
VmallocUsed: 0 kB
VmallocChunk: 0 kB

15.05:

VmallocTotal: 1048372 kB
VmallocUsed: 1644 kB
VmallocChunk: 1028204 kB