"Cannot allocate memory" error when memory is enough

Hi all,

Greeting from me!

I am running OpenBSD 6.3, and don't know from when, loading some
binary will prompt "Cannot allocate memory":

$ egdb
ksh: egdb: Cannot allocate memory

$ cmake
ksh: cmake: Cannot allocate memory

But the memory seems enough:
$top
......
Memory: Real: 57M/1365M act/tot Free: 2546M Cache: 925M Swap: 0K/4103M
......

I try to use "ktrace/kdump" tool, but can't find something special:
......
21881 ktrace NAMI "/usr/local/bin/egdb"
21881 ktrace RET execve -1 errno 12 Cannot allocate memory
......

Could anyone give some clues? Thanks very much in advance!
Best Regards
Nan Xiao