These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.05 s (backtrack: 0/20).

[ebuild  N     ] dev-libs/libaio-0.3.113_p8::gentoo  USE="-static-libs -test" 74 KiB
[ebuild  N     ] dev-lang/luajit-2.1.1787165859:2/2.1.1787165859::gentoo  USE="-lua52compat -static-libs" 1078 KiB
[ebuild  N     ] dev-libs/concurrencykit-0.7.2-r1::gentoo  252 KiB
[ebuild  N     ] app-benchmarks/sysbench-1.0.20-r101::gentoo  USE="aio largefile -attachsql -drizzle -mysql -postgres -test" LUA_SINGLE_TARGET="luajit" 1475 KiB

Total: 4 packages (4 new), Size of downloads: 2877 KiB