@Dongho Kim you could set the value you desire in the default

osquery.flags

file,

/etc/osquery/osquery.flags

on linux,

C:\Program Files\osquery\osquery.flags

on Windows, and.. I think

/var/osquery/osquery.flags

on macos. Set

read_max=[Your Value]

and whenever you start osquery, it should resolve the default flags file and load that value