Hello,
doc/src/smgl/config.sgml: line 2049 for postgres 9.6 states: "Whenever more than backend_flush_after bytes have been written...", which suggests that the data is interpreted as bytes. However the by initdb generated postgresql.conf file mentions that backend_flush_after is in pages, and pg_settings says the unit is 8kB.
Please rephrase doc/src/smgl/config.sgml to state, that the unit for backend_flush_after is not bytes, but pages.
Kind regards
Dilian